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Dissertations / Theses on the topic 'Nanoparticles polymer nanocomposites'

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Published: 6 September 2023

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1

Paul, Anita N. "Silver-Polymer Nanocomposites." Digital Commons @ East Tennessee State University, 2016. https://dc.etsu.edu/etd/3077.

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The objective of this research was the development of an efficient method for the preparation of silver-polymer nanocomposites containing finely dispersed silver nanoparticles. The surface of nanosilver was functionalized by thiolation with 2-aminoethanethiol. Amino-modified nanosilver was covalently bonded to polyacrylic acid, biodegradable polymers like acid terminated polylactic acid, ester terminated poly(DL-lactide-co-glycolide) and acid terminated poly(DL lactide-co-glycolide) in the presence of diisopropylcarbodiimide by carbodiimide method. Esterification of the carboxyl groups of Ag-polyacrylic acid by hydrochloric acid in methanol resulted in the formation of a stable colloidal dispersion of Ag nanoparticles in the polymer matrix. It was observed that not just acid terminated polymers but also ester terminated polymers could react with functionalized nanosilver. This unusual reaction was due to the aminolysis of the ester bond in the polymer chain by the surface amino groups. Silver-polymer nanocomposites obtained with acid terminated polylactic acid and poly(DL-lactide-co-glycolide) contained highly dispersed nanosilver in the polymer matrix in comparison with the ester terminated poly(DL-lactide-co-glycolide). Chemical and structural characteristics of the obtained materials were studied by instrumental methods. Attained biodegradable materials confirmed X-ray contrast and bactericidal properties, which could be eventually used for biomedical applications.
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2

Shepherd, Céline. "New routes for functionalised nanoparticles for polymer nanocomposites." Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:b148b604-80c9-464f-937c-0b3f1553468a.

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Polymer nanocomposites represent a class of advanced, multifunctional materials, combining the attractive features of both nanomaterials and polymers. The level of dispersion of the nanoparticles directly controls the extent to which nanocomposites can maximize the unique attributes of their nano-scale fillers. However, as a consequence of the tendency of nanofillers to agglomerate, the anticipated superior properties of polymer nanocomposites are yet to be realised, and remain merely a theoretical prediction. As a result, the surface chemistry of nanofillers is often tailored to reduce the attractive interparticle interactions that promote agglomeration. This modification can also be used to enhance the interfacial interactions between the nanofiller and polymer matrices to achieve improved filler dispersion. Accordingly, this thesis addresses this challenge in nanocomposite technology by investigating the chemical surface functionalisation of various nanoparticles in order to produce polypropylene (PP) nanocomposites with superior electrical, mechanical and thermal properties. Part I describes covalent modification of nanosilica, microsilica, furnace Carbon Black (CB), acetylene black (ACB) and carbon nanotube (CNT) nanomaterials by carbene insertion and azo-coupling reactions, in a series of studies, in order to tailor their surfaces for application in polypropylene (PP) nanocomposites. The surface characterisation of the modified nanomaterials was assessed in detail using XPS, CHN, SSNMR, BET, ATR-IR and thermal analysis techniques. The surface grafting densities were estimated to be of the order of 1013 and 1014 molecules/cm2 and additionally, SSNMR provided direct evidence of the diarylcarbene reaction to the silica surface. Following nanocomposite production with PP by solvent mixing methods, the macroscopic properties were studied demonstrating altered electrical, mechanical and thermal properties following assessment of the DC conductivity, dielectric properties, thermal analysis (TGA, DSC, DMA) and morphological measurements. In particular, the introduction to the CB surface of a diaryl complex with terminal dodecyl hydrocarbon chains demonstrated substantial improvements to the DC electrical and dielectric properties of the PP nanocomposites. Part II explores the non-covalent surface functionalisation of CB and ACB by the physisorption of the non-ionic surfactant Triton-X-100. Various protocols were developed in which an optimal surface loading for CB was determined by treatment at 0.024 mM(aq). In addition, the modification procedure was combined with the granulation protocol of ACB in an effort to evaluate the potential for industrial applications. The degree of surface functionalisation was extensively characterised by BET, XPS, thermal analysis, UV-Vis and ATR-IR analyses. PP nanocomposites produced by solvent and melt mixing methods demonstrated similar conductive properties following the nanoscale modification, however morphological, dielectric and thermal analysis indicated altered interfacial interactions demonstrating improved mechanical properties.
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3

Burgos, Marmol Jose Javier. "Molecular simulation of polymer nanocomposites." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/molecular-simulation-of-polymer-nanocomposites(56a195bb-81ed-4eb8-81d7-b3357d7f2316).html.

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Polymer nanocomposites (PNCs) are hybrid materials incorporating organic or inorganic nanoparticles (NPs) with at least one dimension in the submicron scale. Over the last two decades, these materials have drawn a remarkable attention due to their central role in industrial formulations and technological applications, extending from food packaging to smart coatings. Incorporating nanoparticles (NPs) to a polymer matrix can significantly alter the conformation and the mobility of the polymer chains in their proximity. Moreover, understanding the delicate balance between the enthalpic and entropic interactions is crucial to control and predict the ability of NPs to diffuse and disperse in the polymer matrix. The impact of these interactions on the structure and the dynamics of polymer chains and NPs is fully revealed in how a number of macroscopic properties changes, justifying the high interest on these materials for industrial applications. In this thesis, the impact on the structure, dynamics, viscosity and thermal conductivity of a number of microscopic properties is investigated by performing Molecular Dynamics (MD) simulations. Specifically, the PNC is represented by a coarse-grained model of a melt of linear homopolymer chains containing spherical NPs. Throughout this work, a number of parameters are modified in order to unveil possible patterns in the PNC’s performance. To this end, this work focuses on the consequences of modifying the NP size dispersity, NP-polymer chain relative size, and chains’ degree of stiffness. Four theoretical models describing the diffusivity of NPs, three of which include nano-scale corrections, have been averaged to study the dependence of dilute NPs’ diffusivity on the NP polydispersity index. By comparing these models to the simulation results at different degrees of polydispersity, it is possible to obtain a more complete picture of their validity as compared to the monodisperse case. Regarding the diffusion of polymer chains, simulation results were in good agreement with the experimental results previously obtained by Composto and coworkers (Soft Matter 2012, 8, 6512), which relate the chains’ diffusivity to the average interparticle distance. As far as the transport properties are concerned, they show a weaker dependence on the polydispersity index. By contrast, results on viscosity and thermal conducitivity show that they are conditioned by the polymer-NP specific interfacial area and the inverse average mass, respectively. These results are in good agreement with previous experimental results. A deeper examination of this intriguing deviation from viscosity predictions in traditional composites, reveals a non-trivial combination of thickening and thinning effects contributing to the final viscosity of the PNC. This thesis also address the influence of the chains’ stiffness on the dynamical and viscous behaviour. An isotropic-to-nematic phase transition is observed, regardless of the NP-monomer interactions, below which a monotonic increase of both properties is observed, whereas orientationally ordered systems dramatically modify them, resulting into a steep increase or a smooth decrease depending on the direction in which they are measured.
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4

Kim, Philseok. "Surface modification of nanoparticles for polymer/ceramic nanocomposites and their applications." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/31651.

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Thesis (Ph.D)--Chemistry and Biochemistry, Georgia Institute of Technology, 2009.
Committee Chair: Perry, Joseph W.; Committee Member: Kippelen, Bernard; Committee Member: Lyon, L. Andrew; Committee Member: Marder, Seth R.; Committee Member: Whetten, Robert L. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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5

Samchenko, Yu M., S. O. Kryklia, T. P. Poltoratska, Леонід Федорович Суходуб, Леонид Федорович Суходуб, Leonid Fedorovych Sukhodub, Yu O. Isheikina, V. I. Makarenko, and V. V. Konovalova. "Hybrid Hydrogel Materials with Incorporated Nanoparticles." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35464.

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Synthesis and physico-chemical studies of new promising hybrid hydrogels based on polyvinyl alcohol (PVA) acetales and copolymer hydrogels based on vynil monomers have been studied. Acrylamide and Acrylnitrile were used as some of components that carry various fillers . Sponge acetales of polyvinyl alco-hol were used as enforcing net. The synthesized composites demonstrated high strength as compared to standard hydrogels- Yung-module varied in the range of 80 to 300 kPa depending on the extent of PVA ac-etale matrix filling with hydrogel component. The materials showed high sorbability to water and water solutions. Study of swelling kinetics as compared to solvents of various nature (water, ethanol, sunflower oil ) was carried out. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35464
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6

Vitoux, Pauline. "Élaboration de nanocomposites "nanoparticules métalliques / polymère" en milieux fluides supercritiques." Phd thesis, Université Sciences et Technologies - Bordeaux I, 2008. http://tel.archives-ouvertes.fr/tel-00627637.

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Structurer les matériaux composites, pour au moins une des phases, à l'échelle nanométrique, c'est-à-dire former des matériaux nanocomposites, est une voie pour optimiser nombre de leurs propriétés. Le domaine de la propulsion et des propergols n'échappe pas à cette règle. C'est dans ce contexte que s'est déroulée cette thèse sur la synthèse de nanocomposites 'nanoparticules métalliques/polymère' en milieux fluides supercritiques (FSCs). Les principales étapes rencontrées dans l'élaboration de nanocomposites en milieu scCO2 ont été étudiées : i) Etude thermodynamique des systèmes polymère/scCO2, ii) Mesure de leur viscosité et iii) Synthèse de nanoparticules inorganiques dans des polymères en milieux FSCs. De plus, une partie importante de la thèse a concerné la synthèse de nanoparticules d'aluminium en milieux fluides supercritiques en vue de leur intégration dans des matrices polymères pour des applications propergols.
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7

Mbese, Johannes Zanoxolo. "Synthesis and characterization of metal sulfide nanoparticles/polymer nanocomposites." Thesis, University of Fort Hare, 2013. http://hdl.handle.net/10353/d1016190.

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The focus of this project was to synthesize and characterize metal sulfide nanoparticles /polymer nanocomposites. The work involved the synthesis of dithiocarbamato ligands and complexes derived from aniline. Zn(II), Cd(II) and Hg(II) dithiocarbamato complexes were used as single-molecule precursors for the synthesis of the ZnS, CdS and HgS nanoparticles and their optical and structural properties studied. The other focus of this work was to synthesize a combined functionality metal sulfide nanoparticles/polymer nanocomposites by dispersing as-synthesized ZnS, CdS and HgS nanoparticles in polymethyl methacrylate (PMMA) matrix. The characterization of the ligands, complexes, nanoparticles and nanocomposites were investigated using relevant instrumental tools like UV-Vis, photoluminescence (PL), Fourier transform infrared (FTIR), X-ray diffraction (XRD), energy dispersion X-ray (EDX), nuclear magnetic resonance (NMR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM).
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8

Yourdkhani, Mostafa. "Aspects of nanoparticles dispersion and interaction in polymer nanocomposites." Thesis, McGill University, 2014. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=123090.

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Polymer nanocomposites have attracted a great deal of attention during the past few decades. Benefiting from the nanoscale geometry, immense surface-to-volume ratio, and exceptional chemical and physical properties, nanoparticles are theoretically expected to enhance the performance of polymer systems. In practice, the preparation of polymer nanocomposites brings its own challenges. To achieve the best reinforcing effect, nanoparticles should be uniformly dispersed within the polymer matrix, and effectively interact with the polymer chains. The strong attractive forces that exist at molecular levels between the nanoparticles through their extensive interfacial area make it very challenging to overcome these issues. Furthermore, the presence of nanoparticles in the polymer matrix significantly alters the processing condition of the polymer system. Therefore, the main objective of this thesis is to investigate the dispersion and interfacial interactions in polymer nanocomposites. To avoid the uncertainties associated with the visual and qualitative analysis of dispersion, which is commonly used by the researchers, a robust algorithm was developed to automatically quantify the state of dispersion in optical and electron micrographs. Several experiments were carried out to perceive the influence of surface modification of nanoparticles on the performance of polymer nanocomposites. Two different material systems were examined: organoclay-modified polylactide (PLA), and carbon nanotube (CNT)-modified epoxy. It was shown that the proper surface modification of nanoparticles could facilitate the dispersion, and consequently, enhance the mechanical and physical performance of the host polymer. To understand the effect of processing conditions on the dispersion quality of nanocomposites, a systematic study on the dispersion stability of CNT-modified epoxy resin was performed. It was found out that at elevated temperatures, CNTs show little affinity for the resin; thereby, any factors that promote the possibility of contacts between the nanotubes may result in their reagglomeration. Consequently, during processing, the dispersion stability is highly influenced with the flow-induced mobility of nanotubes resulting from external shear forces or a change in the viscosity. The insights gained throughout this investigation can be used to optimize the processing conditions and manufacturing methods for maintaining a stable dispersion during processing, and consequently obtaining nanocomposites with enhanced performance.
Les polymères nano-renforcés ont attiré beaucoup d'attention au cours des dernières décennies. Profitant de la géométrie à l'échelle nanométrique, immense rapport surface/volume, et les propriétés chimiques et physiques exceptionnelles, les nanoparticules améliorent en théorie la performance des systèmes de polymères. Dans la pratique, la préparation de polymères nano-renforcés comporte ses propres défis. Pour obtenir le meilleur renforcement possible, les nanoparticules doivent être uniformément dispersées dans la matrice, afin d'interagir efficacement avec les chaînes du polymère. Les forces d'attraction moléculaires qui existent à l'interface entre différentes nanoparticules rendent ces problèmes difficiles à surmonter. En outre, la présence de nanoparticules dans la matrice modifie de manière significative les procédés de fabrication de ce système polymère. Par conséquent, l'objectif principal de cette thèse est d'étudier la dispersion et les interactions interfaciales dans les polymères nano-renforcés. Pour éviter les incertitudes liées à l'analyse visuelle et qualitative de la dispersion, utilisée couramment par les chercheurs, un algorithme robuste a été développé pour quantifier automatiquement l'état de dispersion dans les micrographies optiques et électroniques. Plusieurs expériences ont été réalisées pour comprendre l'influence de la modification de surface des nanoparticules sur la performance des polymères nano-renforcés. Deux matériaux différents ont été examinés: un polylactide (PLA) renforcé avec des organo-argiles, et un époxy renforcé par des nanotubes de carbone (CNT). Il a été démontré qu'une modification appropriée de la surface des nanoparticules pourrait faciliter la dispersion, et par conséquent pourrait améliorer les performances mécaniques et physiques du matériau. Pour comprendre l'effet des procédés de fabrication sur la dispersion des polymères nano-renforcés, une étude systématique sur la stabilité de la dispersion de résine époxyde renforcée par des CNT a été effectuée. Il a été constaté que, à des températures élevées, les nanotubes de carbone présentent peu d'affinité avec la résine, et de ce fait, tous les facteurs qui favorisent la possibilité de contacts entre nanotubes peuvent conduire à leur ré-agglomération. Par conséquent, pendant le procédé de fabrication, la stabilité de la dispersion est fortement influencée par la mobilité induite par l'écoulement de nanotubes résultant de forces de cisaillement externes ou un changement de la viscosité. Les connaissances acquises tout au long de cette enquête peuvent être utilisés pour optimiser les procédés et les méthodes de fabrication afin de maintenir une dispersion stable tout au long de la fabrication, et obtenir ainsi un polymère nano-renforcé avec des performances accrues.
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9

Cipriano, Bani Hans. "Structure and properties of polymer nanocomposites containing anisotropic nanoparticles." College Park, Md.: University of Maryland, 2007. http://hdl.handle.net/1903/7608.

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Thesis (Ph. D.) -- University of Maryland, College Park, 2007.
Thesis research directed by: Dept. of Chemical and Biomolecular Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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10

Smith, Jon Anthony. "Polyaniline Gold Nanocomposites." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/4900.

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Polyaniline/Gold Nanocomposites J. Anthony Smith 141 Pages Directed by Dr. Ji and #345;?anata The expectation that it is possible to create a range of new materials from two basic components, polyaniline fibers and gold particles is explored. Three synthetic methods were employed each of which created different materials and required different investigation techniques. The methods are: chemical, one step aniline oxidation / AuCl4- reduction; electrochemical/chemical, a two-step composite growth achieved by electrochemical polyaniline thin film growth followed by film immersion in AuCl4- solution and spontaneous reduction to gold particles; electrochemical, resulting in freestanding polyaniline thin film/Au nanoparticles carried out by electrochemical stripping of a polyaniline thin film grown over a sacrificial gold layer in the presence halide solutions. The incorporation of particles was shown to affect film morphology and electrical properties in all synthetic methods. The changes are in large part attributed to the development of a contact potential between the polyaniline and the gold particles. Applications for the composites include use as chemically sensitive layers, corrosion inhibition materials, and use as probes to evaluate nanoparticle substrate interactions.
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Inglefield, Jr David Lott. "Tailoring Intermolecular Interactions for High-Performance Nanocomposites." Diss., Virginia Tech, 2001. http://hdl.handle.net/10919/64411.

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Acid oxidation of multi-walled carbon nanotubes (MWCNTs) introduced carboxylic acid sites onto the MWCNT surface, which permitted further functionalization. Derivatization of carboxylic acid sites yielded amide-amine and amide-urea functionalized MWCNTs from oxidized precursors. Conventional MWCNT characterization techniques including X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and Raman spectroscopy supported successful MWCNT functionalization. Incorporation of MWCNTs functionalized with hydrogen bonding groups into a segmented polyurethane matrix led to an increase in mechanical properties at optimized MWCNT loadings, in contrast with non-functionalized MWCNTs that resulted in mechanical property decreases across all loadings. Dynamic mechanical analysis (DMA) demonstrated an increase in the polyurethane-MWCNT composite flow temperature with increasing hydrogen bonding MWCNT incorporation, as opposed to non-functionalized MWCNT composites which displayed no significant change in flow temperature. Variable temperature Fourier transform infrared spectroscopy (VT FT-IR) probed temperature-dependent hydrogen bonding in the polyurethane-MWCNT composites and revealed a significant impact on composite hydrogen bonding interactions upon MWCNT incorporation, which was amplified in composites formed using hydrogen bonding functionalized MWCNTs. Acid oxidation of carbon nanohorns (CNHs) yielded carboxylic acid functionalized CNHs, providing sites for further reaction with histamine to afford histamine-functionalized CNHs (His-CNHs). Raman spectroscopy, XPS and TGA confirmed successful functionalization. Transmission electron microscopy (TEM) demonstrated that His-CNHs efficiently complex quantum dots (QDs) through imidazole-Zn interactions. Combination of His-CNHs, QDs, and a poly(oligo-(ethylene glycol9) methyl ether methacrylate)-block-poly(4-vinyl imidazole) copolymer using an interfacial complexation technique afforded stable ternary nanocomplexes with average hydrodynamic diameters under 100 nm. These ternary nanocomplexes represent promising materials for photothermal cancer theranostics due to their size and stability. The efficient reaction of 2-isocyanatoethyl methacrylate with amines afforded urea-containing methacrylic monomers, where the amine-derived pendant groups determined the polymer Tg. Reversible addition-fragmentation chain-transfer (RAFT) polymerization enabled the synthesis of ABA triblock copolymers with urea-containing methacrylic outer blocks and poly(2-ethylhexyl methacrylate) inner blocks. These ABA triblocks copolymers displayed composition dependent phase-separated morphologies and desirable mechanical properties. The urea-containing polymers efficiently complexed gold nanoparticles through urea-gold interactions. Furthermore, urea-containing methacrylic polymers served as a useful matrix for incorporation of silica-coated upconverting nanoparticles, affording upconverting nanoparticle composite films.The novel ionene monomer N1,N2-bis(3-(dimethylamino)propyl)oxalamide permitted synthesis of novel oxalamide-containing ammonium ionenes. The hydrogen bonding, charge density, and counter anion tuned the ionene mechanical properties. The ionene structure also influenced water uptake and conductivity. The differences in physical properties correlated well with the morphology observed in small-angle X-ray scattering. The oxalamide-containing ionenes greatly enhance mechanical properties compared to typical ammonium ionenes, and further expand the library of ionene polymers.
Ph. D.
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12

Inglefield, David Lott Jr. "Tailoring Intermolecular Interactions for High-Performance Nanocomposites." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/64411.

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Acid oxidation of multi-walled carbon nanotubes (MWCNTs) introduced carboxylic acid sites onto the MWCNT surface, which permitted further functionalization. Derivatization of carboxylic acid sites yielded amide-amine and amide-urea functionalized MWCNTs from oxidized precursors. Conventional MWCNT characterization techniques including X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and Raman spectroscopy supported successful MWCNT functionalization. Incorporation of MWCNTs functionalized with hydrogen bonding groups into a segmented polyurethane matrix led to an increase in mechanical properties at optimized MWCNT loadings, in contrast with non-functionalized MWCNTs that resulted in mechanical property decreases across all loadings. Dynamic mechanical analysis (DMA) demonstrated an increase in the polyurethane-MWCNT composite flow temperature with increasing hydrogen bonding MWCNT incorporation, as opposed to non-functionalized MWCNT composites which displayed no significant change in flow temperature. Variable temperature Fourier transform infrared spectroscopy (VT FT-IR) probed temperature-dependent hydrogen bonding in the polyurethane-MWCNT composites and revealed a significant impact on composite hydrogen bonding interactions upon MWCNT incorporation, which was amplified in composites formed using hydrogen bonding functionalized MWCNTs. Acid oxidation of carbon nanohorns (CNHs) yielded carboxylic acid functionalized CNHs, providing sites for further reaction with histamine to afford histamine-functionalized CNHs (His-CNHs). Raman spectroscopy, XPS and TGA confirmed successful functionalization. Transmission electron microscopy (TEM) demonstrated that His-CNHs efficiently complex quantum dots (QDs) through imidazole-Zn interactions. Combination of His-CNHs, QDs, and a poly(oligo-(ethylene glycol9) methyl ether methacrylate)-block-poly(4-vinyl imidazole) copolymer using an interfacial complexation technique afforded stable ternary nanocomplexes with average hydrodynamic diameters under 100 nm. These ternary nanocomplexes represent promising materials for photothermal cancer theranostics due to their size and stability. The efficient reaction of 2-isocyanatoethyl methacrylate with amines afforded urea-containing methacrylic monomers, where the amine-derived pendant groups determined the polymer Tg. Reversible addition-fragmentation chain-transfer (RAFT) polymerization enabled the synthesis of ABA triblock copolymers with urea-containing methacrylic outer blocks and poly(2-ethylhexyl methacrylate) inner blocks. These ABA triblocks copolymers displayed composition dependent phase-separated morphologies and desirable mechanical properties. The urea-containing polymers efficiently complexed gold nanoparticles through urea-gold interactions. Furthermore, urea-containing methacrylic polymers served as a useful matrix for incorporation of silica-coated upconverting nanoparticles, affording upconverting nanoparticle composite films.The novel ionene monomer N1,N2-bis(3-(dimethylamino)propyl)oxalamide permitted synthesis of novel oxalamide-containing ammonium ionenes. The hydrogen bonding, charge density, and counter anion tuned the ionene mechanical properties. The ionene structure also influenced water uptake and conductivity. The differences in physical properties correlated well with the morphology observed in small-angle X-ray scattering. The oxalamide-containing ionenes greatly enhance mechanical properties compared to typical ammonium ionenes, and further expand the library of ionene polymers.
Ph. D.
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Wilson, Jessica L. "Synthesis and magnetic properties of polymer nanocomposites." [Tampa, Fla.] : University of South Florida, 2004. http://purl.fcla.edu/fcla/etd/SFE0000380.

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Wåhlander, Martin. "Controlled Polymer Grafting from Nanoparticles for the Design of Dielectric Nanocomposites." Doctoral thesis, KTH, Ytbehandlingsteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-204036.

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The interest for polymeric nanocomposites has rapidly grown during the last decades, fuelled by the great potential and superior properties of nanoparticles (NPs). The production volumes of commercial NPs have increased exponentially during the last ten years, and the quality has been significantly improved. The aim of this study was to design polymer grafted commercially available metal-oxide NPs, and graphene oxide (GO), to develop isotropic (homogeneous) and anisotropic (heterogeneous) polymer nanocomposites for dielectric applications. The motivation was to formulate functional insulation materials for compact components in future power-grid systems using high-voltage direct-current (HVDC) or high-voltage alternating-current (HVAC), and to fabricate responsive sensor materials for monitoring e.g. temperature and voltage fluctuations in so called “Smart Grids”. Aluminium oxide (Al2O3), zinc oxide (ZnO) and reduced GO (rGO) NPs were modified with sparse polymer grafts via a controlled “covalent route” and were mixed with silicone (PDMS) or polyethylene matrices (EBA and LDPE) commonly used in HV-cable systems. The graft length and the graft-to-matrix compatibility were tailored to obtain nanocomposites with various self-assembled NP-morphologies, including well-dispersed, connected and phase-separated structures. The graft length was used to adjust the inter-particle distance of nanocomposites with continuous morphologies or connected (percolated) NPs. It was found that nanocomposites with percolated NPs and short inter-particle distances exhibited 10-100 times higher conductivity than the unfilled (neat) polymer, or displayed a rapid non-linear increase in conductivity (~1 million times) with increasingelectric field, while well-dispersed NPs with long inter-particle distances exhibited 10-100 times lower conductivity (i.e. higher resistivity) as an effect of their trapping of charge carriers. These tunable and functional properties are desirable for HV-insulation, field-grading applications, and flexible electronics. In addition it was shown that GO modified with dense polymer grafts via a “physisorption route” formed suspensions with liquid crystals, or matrix-free GO-composites with well-dispersed GO in isotropic or nematic states. These materials were reinforced by the GO, and exhibited elevated glass transition temperatures and a rapid thermo-responsive shape-memory effect, and are thus proposed to have a great potential as sensor materials and responsive separation membranes.
Intresset för polymera nanokompositer har snabbt ökat under de senaste decennierna, drivet av den stora potentialen och de överlägsna egenskaperna hos nanopartiklar (NPs). Produktionsvolymerna för kommersiella NP har ökat exponentiellt under de senaste tio åren, och kvaliteten har förbättrats avsevärt. Syftet med denna studie var att polymer-ympa kommersiellt tillgängliga metalloxid-NPs, och grafenoxid (GO), för att designa isotropa (homogena) och anisotropa (heterogena) polymera nanokompositer för dielektriska tillämpningar. Motiveringen var att formulera funktionella isoleringsmaterial för kompakta komponenter i framtida kraftnätssystem som använder högspänd likström (HVDC) eller högspänd växelström (HVAC), samt att tillverka responsiva sensormaterial för övervakning av t.ex. temperatur- and spänningsvariationer i så kallade "Smart Grids". Aluminiumoxid (Al2O3), zinkoxid (ZnO) och reducerad GO (rGO) NPs modifierades med glesa polymerympar via en kontrollerad "kovalent väg" och blandades med silikon (PDMS) eller polyeten matriser (EBA och LDPE) som är vanliga i HV-kabelsystem. Ymplängden och ymp-till-matrix kompatibiliteten skräddarsyddes för att erhålla nanokompositer med olika självordnande NP-morfologier, inklusive väldispergerade, länkade och fasseparerade strukturer. Ymplängden användes för att justera partikelavståndet i nanokompositer med förbundna morfologier eller länkade NPs. Man fann att nanokompositer med länkade NPs och korta interpartikelavstånd uppvisade 10-100 gånger högre konduktivitet än den ofyllda (rena) polymeren, eller erhöll en snabb icke-linjär ökning i konduktivitet (~1 miljon gånger) med ökande elektriskt fält, medan väldispergerade NPs med långa interpartikelavstånd uppvisade 10-100 gånger lägre ledningsförmåga (dvs. högre resistivitet) som en effekt av deras infångande av laddningsbärare. Dessa inställbara och funktionella egenskaper är önskvärda för HV-isolering, fältstyrande applikationer och flexibel elektronik. Dessutom visades att GO, som modifierats med täta polymerympar via en "fysisorptionsväg", bildade suspensioner med flytande kristaller, eller matrisfria GO-kompositer med väldispergerad GO i isotropa eller nematiska tillstånd. Dessa material armerades av GO och uppvisade förhöjda glastransitionstemperaturer och en snabb värmeresponsiv form-minneseffekt, och föreslås därigenom ha en stor potential som sensor-material och responsiva separationsmembran.

QC 20170323

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Cheerarot, Onanong. "The effects of nanoparticles on structure development in immiscible polymer blends." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/the-effects-of-nanoparticles-on-structure-development-in-immiscible-polymer-blends(cca9d075-dfcd-46c5-b865-290c414b4315).html.

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Composites based on binary polymer blends of polystyrene (PS)/poly(ethylene-co-vinyl alcohol) (EVOH) (70/30 wt%) containing natural Montmorillonite, Na-MMTs (Nanomer PGW or Cloisite Na+) and organically modified Montmorillonite clays, OMMTs (Nanomer I.30T, Cloisite 30B or Cloisite 10A) were prepared via melt compounding. The interactions between the polymers and clays were studied using flow micro-calorimetry (FMC). Data obtained from FMC indicated that the probe molecule mimicking EVOH (butan-2-ol) interacted with the MMTs and OMMTs much more strongly than PS. Scanning electron microscopy (SEM) revealed that composites based on binary blends had dispersed/continuous morphologies, in which EVOH was dispersed in a PS matrix. The size of the EVOH droplets in the PS matrix increased with increasing clay loading. Transmission electron microscopy (TEM) and wide angle X-ray diffraction (WAXD) were used to determine the extent of dispersion and location of clay in the PS/EVOH/clay composites. These techniques confirmed the formation of intercalated clay structures. As predicted by FMC, the clay platelets were selectively located in the EVOH phase, independent of the blending sequence and the type of organic modifier in the OMMT. Composites containing OMMTs showed better dispersion of platelets within the EVOH phase than those containing Na-MMTs. Differential scanning calorimetry (DSC); showed the crystallisation behaviour of EVOH to depend on the clay loading and the nature of the organic modifier in the OMMT. Nanomer PGW, Cloisite Na+ and Cloisite 30B acted as weak nucleating agents. In contrast, Nanomer I.30T and Cloisite 10A significantly hindered the crystallisation of EVOH in the blends due to the restriction of chain segment mobility. Dynamic mechanical thermal analysis (DMTA) confirmed that the presence of clay increases the storage modulus of the composites compared to an unfilled blend. In addition, the improvement in storage modulus reflected the dispersion state of the different clays and their interaction with the polymers of the blend. Ternary-blend based composites were formed by adding poly(styrene-co-acrylonitrile) (SAN) to the composites based on binary PS/EVOH blends. This resulted in a finer dispersion of the EVOH phase and the development of a core-shell morphology, in which SAN encapsulated and formed shells around EVOH droplets. In contrast to binary blend composites, the clay platelets were found at the interface between SAN and EVOH in the ternary blends.
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16

Wang, Nannan. "Carbon-coated nanoparticles and their application in high performance polymer nanocomposites." Thesis, University of Exeter, 2018. http://hdl.handle.net/10871/33110.

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Shrinking down into nanoscale, materials exhibit huge property advantages over their bulk form. New forms of carbon at nanoscale have occupied the prominent position in modern materials research. With a very long history accompanying our human civilisation, carbon as a wonder material has once again contributed to our technological advances, as evidenced by the discoveries and research attractions in the last a few decades. Research into fullerenes (C60, C70, etc.), carbon nanotubes (CNTs) and graphene has been continued raising, because of the numerous novel properties associated with these new carbon forms1-3. On top of their excellent electronical, physical and chemical properties, CNTs and graphene also exhibit excellent mechanical properties including ultra-high tensile strength, Young’s Modulus, as well as high thermal conductivities. Research into carbon has also promoted the flourish of many new non-carbon nanomaterials, and typical examples include the inorganic fullerene-like tungsten disulphide (IF-WS2) nanoparticles (NPs), numerous oxide NPs and nanowires that also exhibit various remarkable properties, such as high hardness and anti-oxidation stability. To combine the outstanding performances of both carbon and non-carbon nanomaterials by marrying nanoscale carbon with various metal oxide particles, which forms the backbone of my thesis by carrying out the intensive investigations. In my project it have further validated the advantages of the resulting new carbon-coated NPs in different polymeric matrix composites. The main findings are as follows: 1. A home-made rotary chemical vapour deposit (RCVD) system has been modified and this versatile facility has been applied successfully to produce different types of graphitic carbon-coated nanocomposite particles, from micro- down to nano-scale, including IF-WS2, TiO2, ZnO, Y2O3, Cr2O3, CeO2 and ZrO2 etc. The production can be up to 30 g/per batch, which is 10s times more than using a traditional static furnace, by avoiding severe agglomeration. 2. The resulting coating consists of a few layered graphitic carbon with lattice space 0.34 nm. The thickness of the coating is simply controllable between 1-5 nm, depending on the deposition time (10~60 min), precursor injection flow rate (1.2~2.4 ml/L) and heating temperature (700~900 oC). Furthermore, the oxide core of ZnO@C was removed by heating under the H2/Ar atmosphere, and have successfully generated nano- to micro-scale, hollow, closed, and all-carbon structures. 3. The commercial Nylon 12 is applied to fabricate the metal oxide polymer composite. Using ZnO@C-Nylon 12 composite as an example, at 2 wt% content, the composites have achieved with the ultimate tensile strength increased by 27% (from 47.9 to 59.6 MPa), In particular, at 4 wt% content, the ZnO@C showed an impressive improvement in thermal conductivity of nearly 50% (From 0.21 t0 0.31 W∙m-1∙K-1), comparing 16% improvement for ZnO-Nylon 12 composite. 4. Apart from investigations of nylon composite, intensive studies of the Poly ether ether ketone (PEEK), an important high performance engineering thermoplastics polymer, and its nanocomposites reinforced by IF-WS2 and IF-WS2@C have been carried out in this thesis. The IF-WS2/PEEK composites exhibited not only an improvements of 24% (From 77.6 to 96.7 MPa) in the tensile strength (2 wt%), but also showed an extraordinary increase in thermal conductivity by 190%, from 0.248 to 0.719 W∙m-1∙K-1 at 8 wt%, higher onset decomposing temperatures (54 oC) against the plain PEEK. 5. Moreover, owing to the better dispersal capacity of IF-WS2@C NPs, the ternary IF-WS2@C-PEEK nanocomposites produced in this thesis displayed impressive mechanical properties, increased by 51% (From 77.6 to 120.9 MPa, at 2 wt%), and extremely greater thermal conductivity, with 235% (From 0.248 to 0.831 W∙m-1∙K-1 at 8 wt%), and better stability than the comparison IF-WS2-PEEK composites. The parameters influencing the coating quality and thickness have also been investigated. Further, their interface studies based on the FTIR and XPS techniques have verified the formation of chemical bonding (C=S bonding and carbon π-π bonding), rather than physically bonded together. The successful application of the generic RCVD process can be further extended to the processing of many new particles for an ultrathin carbon coating. Considering the vast amount of literature focusing on carbon, the project further processing of carbon-coated materials in composites could easily be tailored to achieve desired surface contacts with different matrices and leading to the better desired performance, as verified in this thesis for the advanced binary and ternary composites. Finally, this research is expecting to expand the application potentials of PEEK-based nanocomposites in critical areas where thermal conductivity and thermal stability are important.
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17

Dzhardimalieva, G. I., and A. D. Pomogailo. "Polymer-Assisted Synthesis, Structure and Properties of Metal Nanocomposites." Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/35061.

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We have elaborated methods for synthesis of macromolecular metal complexes via homo- and copolymerization of metal-containing monomers (unsaturated metal carboxylates, metal nitrates acrylamide complexes. Thermal transformations of such compounds possess the unique way for preparation of nanocomposite materials when metal (or their oxides and carbides) nanoparticles and a stabilizing polymer matrix are formed simultaneously in situ. Molecular and supramolecular organization of nanocomposites obtained can be controlled during the thermal transformation of such monomers in inert or self-generated atmosphere. The process includes three macrostages: dehydration, solid-phase polymerization, and pyrolysis of the polymer products formed. The approach makes it possible to adjust the mean particle size in a given range by just choosing the appropriate reaction conditions. The composition of metal nanoparticles, their size and distribution on the size as well as the type and thickness of polymer shell can be controlled on the stage of nanocomposite formation. The nanocomposites obtained reveal ferromagnetic behaviour at room temperature with high coercive force and magnetic anisotropy. With aim to control the composition and structure (for example, core-shell type) of ferromagnetic nanomaterials obtained as well as their properties, the reaction conditions such as temperature, ratio of starting compounds, the type of polymer matrix can be varied. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35061
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18

Stojak, Kristen Lee. "Synthesis and Properties of Polymer Nanocomposites with Tunable Electromagnetic Response." Scholar Commons, 2013. http://scholarcommons.usf.edu/etd/4587.

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Multifunctional polymer nanocomposites (PNCs) are attractive for the design of tunable RF and microwave components such as flexible electronics, attenuators, and antennas due to cost-effectiveness and durability of polymeric matrices. In this work, three separate PNCs were synthesized. Magnetite (Fe3O4) and cobalt ferrite (CFO) nanoparticles, synthesized by thermal decomposition, were used as PNC fillers. Polymers used in this work were a commercial polymer provided by the Rogers Corporation (RP) and polyvinylidene fluoride (PVDF). PNCs in this thesis consist of Fe3O4 in RP, CFO in RP, and Fe3O4 in PVDF. Characterization techniques for determining morphology of the nanoparticles, and their resulting PNCs, include x-ray diffraction, transmission electron microscopy and magnetometry. All magnetometry measurements were taken using a Quantum Design Physical Property Measurement System with a superconducting magnet. Temperature and external magnetic field magnetization measurements revealed that all samples exhibit superparamagnetic behavior at room temperature. Blocking temperature, coercivity and reduced remnant magnetization do not vary with concentration. Tunable saturation magnetization, based on nanoparticle loading, was observed across all PNCs, regardless of polymer or nanoparticle choice, indicating that this is an inherent property in all similar PNC materials. Tunability studies of the magneto-dielectric PNCs were carried out by adding the PNC to cavity and microstrip linear resonator devices, and passing frequencies of 1-6 GHz through them in the presence of transverse external magnetic fields of up to 4.5 kOe, provided by an electromagnet. Microwave characteristics were extracted from scattering parameters of the PNCs. In all cases, losses were reduced, quality factor was increased, and tunability of the resonance frequency was demonstrated. Strong magnetic field dependence was observed across all samples measured in this study.
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19

Khan, Assad Ullah. "Thin-Film Polymer Nanocomposites Composed of Two-Dimensional Plasmonic Nanoparticles and Graphene." Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/101942.

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Plasmonic polymer nanocomposites contain plasmonic nanoparticles that are dispersed within a polymer. The polymer matrix strongly influences the optical properties of plasmonic nanoparticles. It is imperative to understand the interaction between plasmonic nanoparticles and polymers so that one can develop functional devices using nanocomposites. The utilization of plasmonic nanoparticles as fillers has great potential to transform critical nanotechnologies where light management is crucial, such as refractive index based nanosensors, optical coatings, and light actuated devices. Despite the great potential, effective integration of plasmonic nanoparticles with polymers remains challenging. This dissertation presents i) the effects of dielectric media on the optical properties of plasmonic nanoparticles, ii) the sensing of polymer brush formation on nanoparticles, iii) the fabrication of plasmonic nanocomposite thin-films with controlled optical properties, and iv) the development of electrically conductive membranes for electrostatic speakers. The optical response of plasmonic nanoparticles (referred to as wavelength of localized surface plasmon resonance, λLSPR) is sensitive to changes in refractive index of the medium. The sensitivity (S) plays a critical role in determining the performance of nanoparticles in sensing applications. In this dissertation, I have conducted a systematic study on the sensitivity of plasmonic nanoparticles as a function of various parameters: shape, size, composition, initial plasmonic resonance wavelength, cross-sectional area, and aspect ratio. Among the parameters investigated, aspect ratio (R) is determined to be the key parameter that controls S, following an empirical equation, S = 46.87 R + 109.37. This relationship provides a guideline for selecting fillers in plasmonic polymer nanocomposites, and it predicts the final effect of plasmonic nanoparticles on the optical properties of polymer nanocomposites. Plasmonic nanoparticles are employed to probe polymer grafting on the surfaces of metal nanoparticles. Using ultraviolet-visible (UV-vis) spectroscopy, I have demonstrated the quantification of polymer grafting density on the surface of plasmonic nanoparticles. The λLSPR of plasmonic nanoparticles red-shifts as the polymer concentration near the nanoparticle surface increases. I have investigated the formation of polymer brush by grafting the nanoparticles with thiolated polyethylene glycol (PEG-SH) and revealed the three–regime kinetics in situ. Importantly, this study suggests that a latent regime arises due to fast polymer adsorption and prolonged chain rearrangement on nanoparticle surfaces. When the polymer chains rearrange and chemically tether to the surface, they contract and allow more polymer chains to graft onto the particle surface until saturation. This analytical method provides a new surface probing technique for polymer brush analysis, complementary to conventional methods such as quartz crystal microbalance, atomic force microscope, and microcantilivers. Commercial tinted glass employs expensive metalized films to reduce light transmittance but has limited spectral selectivity. To reduce the cost of metalized films and to improve the spectral selectivity, I have employed plasmonic nanoparticles in polymers to fabricate spectral-selective tinted films. First, I have synthesized two-dimensional (2D) plasmonic silver nanoparticles (AgNPs) using multi-step growth. The nanoparticles have a tunable plasmon resonance and provide spectral selectivity. The multi-step growth forgoes polymeric ligands such as poly(vinylpyrrolidone) (PVP) and solely relies on a small molecule sodium citrate. Briefly, small citrate-capped Ag seeds are first grown into small 2D AgNPs. The small 2D AgNPs are then used to grow large 2D AgNPs via multiple growth steps. The PVP-free method allows for fast synthesis of 2D AgNPs with large sizes and tunable plasmon resonance across the visible and NIR region. The 2D AgNPs are integrated with polymers to produce thin-film plasmonic nanocomposites. By controlling the planar orientation of the 2D AgNPs through layer-by-layer assembly, the polymer nancomposites have achieved reduced light transmittance and enhanced reflectance across the visible and NIR range. In contrast to conventional polymer nanocomposites where the AgNPs are randomly oriented, the thin-film polymer nanocomposites exhibit excellent control over nanoparticle density and hence the optical properties, that is, tunable light transmittance and reflectance across the visible and NIR. Lastly, graphene is used to prepare conductive free-standing polymer thin-films. Graphene, an ultralight weight 2D material with excellent electrical and mechanical properties, has potential for use in thin-film composites essential for photovoltaics, electrostatic speakers, sensors, and touch displays. Current graphene-based composite films contain graphene flakes randomly mixed in a polymer matrix and usually possess poor mechanical and electrical properties. In this dissertation, I have developed thin-film nanocomposites comprised of chemical vapor deposited (CVD) graphene and high-performance polyetherimide (PI). The CVD-grown graphene is polycrystalline, and it cannot be used as a free-standing film. By enforcing the polycrystalline graphene with a thin layer of PI, I have prepared free-standing thin-film composites with a high aspect ratio of 105. Mechanical and electrical property characterization reveals a Young's modulus of 3.33 GPa and a resistance of 200 - 500 Ω across the membrane. A typical spring constant of the membrane is ~387 N/m. Dynamic electromechanical actuation shows that the membrane vibrates at various input frequencies. The polymer/graphene film has excellent acoustic properties, and when used as a speaker membrane, it reduces the electrical power consumption by a factor of 10-100 over the frequency range of 600–10,000 Hz.
Doctor of Philosophy
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20

Fogelström, Linda. "Polymer Nanocomposites in Thin Film Applications." Doctoral thesis, KTH, Ytbehandlingsteknik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-12400.

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The introduction of a nanoscopic reinforcing phase to a polymer matrix offers great possibilities of obtaining improved properties, enabling applications outside the boundaries of traditional composites. The majority of the work in this thesis has been devoted to polymer/clay nanocomposites in coating applications, using the hydroxyl-functional hyperbranched polyester Boltorn® as matrix and montmorillonite clay as nanofiller. Nanocomposites with a high degree of exfoliation were readily prepared using the straightforward solution-intercalation method with water as solvent. Hard and scratch-resistant coatings with preserved flexibility and transparency were obtained, and acrylate functionalization of Boltorn® rendered a UV-curable system with similar property improvements. In order to elucidate the effect of the dendritic architecture on the exfoliation process, a comparative study on the hyperbranched polyester Boltorn® and a linear analogue of this polymer was performed. X-ray diffraction and transmission electron microscopy confirmed the superior efficiency of the hyperbranched polymer in the preparation of this type of nanocomposites. Additionally, an objective of this thesis was to investigate how cellulose nanofibers can be utilized in high performance polymer nanocomposites. A reactive cellulose “nanopaper” template was combined with a hydrophilic hyperbranched thermoset matrix, resulting in a unique nanocomposite with significantly enhanced properties. Moreover, in order to fully utilize the great potential of cellulose nanofibers as reinforcement in hydrophobic polymer matrices, the hydrophilic surface of cellulose needs to be modified in order to improve the compatibility. For this, a grafting-from approach was explored, using ring-opening polymerization of ε-caprolactone (CL) from microfibrillated cellulose (MFC), resulting in PCL-modified MFC. It was found that the hydrophobicity of the cellulose surfaces increased with longer graft lengths, and that polymer grafting rendered a smoother surface morphology. Subsequently, PCL-grafted MFC film/PCL film bilayer laminates were prepared in order to investigate the interfacial adhesion. Peel tests demonstrated a gradual increase in the interfacial adhesion with increasing graft lengths.
QC20100621
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21

Guerra, Dante Rene. "INFLUENCE OF NANOPARTICLES ON THE PHISICAL PROPERTIES OF FIBER REINFORCED POLYMER COMPOSITES." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1259091518.

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22

Chaparro, Dayling L. "Novel Polymer-Metal Nanocomposites for Applications in Detection and Sensing." Scholar Commons, 2007. http://scholarcommons.usf.edu/etd/3900.

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Detection of trace elements such as organic contaminants, explosive residues, and metal ions is an intellectually challenging task in science and engineering. It is also a topic of increasing importance due to its impact on society and the environment. Designing molecularly imprinted materials is one of the most promising approaches to explore sensing and detection applications. “Stimuli-sensitive” polymer materials are ideal candidates for these imprinted sensors as they are able to respond to changes in their environment and can be tailored by cross-linking the polymer chains. The responses can be amplified and transduced into measurable signals due to macromolecular properties provided by the use of a polymer. The purpose of the research in this project is to combine organic polymers with inorganic constituents to tailor the binding properties and the responses of the composite material for detection of metals ions in aqueous solutions. The research, here, is based on a thermally responsive polymer such as poly(Nisopropylacrylamide) (PNIPAM), which exhibits a well-known reversible volume phase transition in aqueous media around approximately 32°C. Combining cross-linked microgels formed from PNIPAM and its copolymers with gold nanoparticles (GNP) imparts the composite material with optical properties such as intense visible absorption due to the unique surface plasmon absorption of these small nanoparticles. The use of copolymers allows incorporation of functional groups, such as carboxylic acid, that are potential sites for binding metal ions. Cross-linking of the metal ion binding polymer imprints the metal ion in the PNIPAM microgel network. In this research, design of the composite material was investigated using copolymers of NIPAM and acrylic acid (AA), copolymers of NIPAM and glycidyl methacrylate (GMA), and interpenetrating networks of PNIPAM and PAA. A broad spectrum of polymerization conditions were studied such as changes in cross-linking density as well as changes in the synthetic procedure. Techniques such as turbidometry, ultraviolet visible spectroscopy (UV-VIS), transmission electron microscopy (TEM), and dynamic light scattering (DLS) were employed to characterize the microgels as well as their composites with GNP. Preliminary investigation of imprinting the microgels with heavy metal ions such as copper was also performed. The novel polymer-metal nanocomposites explored here will serve as an important contribution for the current ongoing research efforts in designing materials in the nano-scale capable of sensing and detecting metal ions in solution with high selectivity.
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23

Gendre, Laura. "A study of emission of nanoparticles during physical processing of aged polymer-matrix nanocomposites." Thesis, Cranfield University, 2016. http://dspace.lib.cranfield.ac.uk/handle/1826/12381.

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Nanotechnology research and its commercial applications have experienced an exponential rise in the recent decades. Although there are a lot of studies with regards to toxicity of nanoparticles, the exposure to nanoparticles, both in terms of quality and quantity, during the life cycle of nanocomposites is very much an unknown quantity and an active area of research. Unsurprisingly, the regulations governing the use and disposal of nanomaterials during its life cycle are behind the curve. This work aims to assess the quantity of nanoparticles released along the life cycle of nanocomposites. Machining operations such as milling and drilling were chosen to simulate the manufacturing of nanocomposites parts, and impact testing to recreate the end-of-life of the materials. Several studies have tried to simulate different release scenarios, however these experiments had many variables and in general were not done in controlled environments. In this study, a reliable method was developed to assess the release of nanoparticles during machining and low velocity impact of nanocomposites. The development and validation of a new prototype used for measurement and monitoring of nanoparticles in a controlled environment is presented, as along with release experiments on different nanocomposites. Every sample tested was found to release nanoparticles irrespective of the mechanical process used or the type of material tested. Even neat polymers released nanoparticles when subjected to mechanical forces. The type of matrix was identified to play a major role on the quantity of nanoparticles release during different process. Thermoset polymers (and especially polyester) were found to release a higher number concentration of particles, mainly due to their brittle properties. A polyester sample was found to release up to 48 times more particles than a polypropylene one during drilling. The nanofiller type and percentage used to reinforce the polymer is also a key point. For example, the addition of 2 wt.% of nano-alumina into polyester increases the number concentration of particles by 106 % following an impact. The nanofiller chosen and its quantity affect the mechanical properties and machinability of the composites and therefore its nanoparticles release potential. The mechanical process and the process parameters chosen were also found to be crucial with regards to the nanoparticles released with different trends observed during drilling and impact of similar materials. Finally, thermal ageing of nanocomposites increases the number concentration of nanoparticles released (by 8 to 17 times after 6 weeks).
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Chen, Hui. "DEVELOPMENT AND APPLICATION STUDY OF NANOSCALE THIN FILM MATERIALS AND POLYMER NANOCOMPOSITES." Doctoral diss., University of Central Florida, 2008. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2124.

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This dissertation demonstrated that the manipulation of substances at the molecular or nanometer level can lead to the discovery and development of new materials with interesting properties and important applications. Chapter 1 describes the development of a nanoscale molecular thin film material for corrosion protection. By using a self-assembled monolayer film with a thickness of only about 1 nanometer as a linkage, a covalent bonding was achieved between a polyurethane top coating and an aluminum alloy substrate. This covalent bonding between polymer top coating and the aluminum alloy substrate significantly improved the corrosion resistance of the substrate. Chapter 2 and Chapter 3 describe the development of a gold nanoparticle-polymer composite material in different forms with a number of applications. Gold nanoparticles are among one of the most extensively studied nanomaterials. When the size of gold is shrunk to the nanometer scale, many interesting and new physical properties start to appear from gold nanoparticles. The optical properties of gold nanoparticles, particularly the surface plasmon resonance absorption, have been investigated in this dissertation for the development of multifunctional nanocomposite materials. Chapter 2 presents the preparation of a gold nanoparticle/poly(methyl methacrylate) (PMMA) nanocomposite film and the application of such films for microstructure fabrication using a direct laser writing technique. Gold nanoparticles are excellent photon-thermal energy converters due to their large absorption cross section at the surface plasmon resonance region. Upon laser irradiation of the nanocomposite film, the thermal energy converted from the absorbed photon energy by gold nanopaticles induced a complete decomposition of PMMA, leading to the formation of various microstructures on the nanocomposite films. Chapter 3 reports the further development of a nanoparticle/polymer composite nanofiber material fabricated through an electrospinning process. The matrix of the nanofiber is made of two polyelectrolytes, poly(acrylic acid) (PAA) and poly(allylamine hydrochloride) (PAH). Three methods were developed to incorporate gold nanoparticles into the polymer matrix. The composite nanofiber materials developed in this study demonstrate multifunctional properties, including good electrical conductivity, photothermal response, and surface-enhanced IR absorption. This material may be used for many important applications including catalysis, chemical and biological sensors, and scaffold materials for tissue engineering. In Chapter 4, another most important nanomaterial, carbon naotubes (CNTs), were introduced as fillers to prepare polymer nanocomposites. A dispersion method for multi-walled carbon nanotubes (MWCNTs) using a conjugated conducting polymer, poly(3-hexylthiophene) (P3HT) as the third component and trifluoroacetic acid (TFA) as a co-solvent was developed. Due to the excellent dispersion of carbon nanotubes in PMMA and enhanced conductivity of the nanocomposites by the conjugated conducting polymers, the prepared composite materials has an extremely low percolation threshold of less than 0.006 wt% of MWCNT content. The potential use of MWCNT/conducting polymer composites for energy storage applications such as suppercapacitors was further investigated by Cyclic Voltammetry (CV), Electrochemical Impedance Spectroscopy (EIS) and charging-discharging cycles. Compared to pure carbon nanotubes, the nanocomposite materials have significantly improved properties and are promising for supercapacitor applications.
Ph.D.
Department of Mechanical, Materials and Aerospace Engineering
Engineering and Computer Science
Materials Science & Engr PhD
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25

Doddapaneni, Venkatesh. "On the polymer-based nanocomposites for electrical switching applications." Doctoral thesis, KTH, Tillämpad fysik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-202702.

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Recent research demonstrated that polymer based nanocomposites (PNCs) have been engineered in order to improve the arc interruption capability of the circuit breakers. PNCs are the combination of nano-sized inorganic nanoparticles (NPs) and polymers, opened up new developments in materials science and engineering applications. Inorganic NPs are selected based on their physical and chemical properties which could make multifunctional PNCs in order to interrupt the electrical arcs effectively. In particular, we presented the PNCs fabricated by using CuO, Fe3O4, ZnO and Au NPs in a poly (methyl methacrylate) (PMMA) matrix via in-situ polymerization method, recently developed method to avoid NPs agglomeration, leading to good spatial distribution in the polymer matrix. Thus, several samples with various wt% of NPs in PMMA matrix have been fabricated. These PNCs have been characterized in detail for the morphology of NPs, interaction between NPs and polymer matrix, and radiative/thermal energy absorption properties. In the next stage, PNCs are tested to determine their arc interruption performance and impact on the electrical arcs of current 1.6 kA generated using a specially designed test set-up. When PNCs interact with the electrical arcs, they generate ablation of chemical species towards core of the electrical arc, resulting in cooling-down the arc due to strong temperature and pressure gradient in the arc quenching domain. This thesis demonstrates for the first time that these engineered PNCs are easily processed, reproducible, and can be used to improve the arc interruption process in electrical switching applications.
Ny forskning har visat att polymerbaserade nanokompositer (PNCs) har utformats för att förbättra strömbrytares förmåga att undvika ljusbågar vid överslag. PNCs är en kombination av nanostora oorganiska nanopartiklar (NP) och polymerer, som har öppnat upp för ny utveckling inom materialvetenskap och tekniska tillämpningar. Oorganiska NP väljs baserat på deras fysikaliska och kemiska egenskaper som kan hjälpa PNCs att motverka elektriska ljusbågar effektivt. I synnerhet, presenterade vi PNCs tillverkade genom användning av CuO, Fe3O4, ZnO och Au NP i en poly (metylmetakrylat) (PMMA)-matris via in situ-polymerisationsmetod, nyligen utvecklad för att undvika NP-agglomerering, vilket leder till god rumslig fördelning i polymermatrisen. Därför har flera prover med olika vikt% av NP i PMMA-matris tillverkats. Dessa PNCs har utvärderats i detalj för NP-morfologi, interaktion mellan NP och polymermatris, och strålnings- och värmeenergiabsorption. I nästa skede testas PNCs för att bestämma deras förmåga att undvika ljusbågar och påverkan på de elektriska ljusbågarna av 1,6 kA strömstyrka, genererade med hjälp av en specialdesignad test-set-up. När PNCs interagerar med de elektriska ljusbågarna, genererar de ablation av kemiska ämnen mot kärnan i den elektriska ljusbågen, vilket resulterar i nedkylning av ljusbågen på grund av starka temperatur- och tryckgradienter i området. Denna avhandling visar för första gången att dessa konstruerade PNCs är lätta att framställa, reproducerbara, och kan användas för att förbättra avbrottsprocessen för ljusbågen i elektriska kopplingstillämpningar.

QC 20170303

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26

Jing, Hengye. "The Interaction of Engineered Nanoparticles with Microbial Biofilm and its Applications." University of Cincinnati / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1511799004863635.

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27

Li, Yonghui. "Biodegradable poly(lactic acid) nanocomposites: synthesis and characterization." Diss., Kansas State University, 2011. http://hdl.handle.net/2097/8543.

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Doctor of Philosophy
Department of Grain Science and Industry
X. Susan Sun
Biobased polymers derived from renewable resources are increasingly important due to acute concerns about the environmental issues and limited petroleum resources. Poly(lactic acid) (PLA) is such a polymer that has shown great potential to produce biodegradable plastics. However, low glass transition temperature (Tg), low thermal stability, slow biodegradation rate, and high cost limit its broad applications. This dissertation seeks to overcome these limitations by reinforcing PLA with inorganic nanoparticles and low-cost agricultural residues. We first synthesized PLA nanocomposites by in situ melt polycondensation of L-lactic acid and surface-hydroxylized nanoparticles (MgO nanocrystals and TiO2 nanowires) and investigated the structure-property relationships. PLA grafted nanoparticles (PLA-g-MgO, PLA-g-TiO2) were isolated from the bulk nanocomposites via repeated dispersion/centrifugation processes. The covalent grafting of PLA chains onto nanoparticle surface was confirmed by Fourier transform infrared spectroscopy and thermalgravimetric analysis (TGA). Transmission electron microscopy and differential scanning calorimetry (DSC) results also sustained the presence of the third phase. Morphological images showed uniform dispersion of nanoparticles in the PLA matrix and demonstrated a strong interfacial interaction between them. Calculation based on TGA revealed that more than 42.5% PLA was successfully grafted into PLA-g-MgO and more than 30% was grafted into PLA-g-TiO2. Those grafted PLA chains exhibited significantly increased thermal stability. The Tg of PLA-g-TiO2 was improved by 7 °C compared with that of pure PLA. We also reinforced PLA with low-value agricultural residues, including wood flour (WF), soy flour (SF), and distillers dried grains with solubles (DDGS) by thermal blending. Tensile measurements and morphological images indicated that methylene diphenyl diisocyanate (MDI) was an effective coupling agent for PLA/WF and PLA/DDGS systems. MDI compatibilized PLA/WF and PLA/DDGS composites showed comparable tensile strength and elongation at break as pure PLA, with obviously increased Young’s modulus. Increased crystallinity was observed for PLA composites with SF and DDGS. Such PLA composites have similar or superior properties compared with pure PLA, especially at a lower cost and higher biodegradation rate than pure PLA. The results from this study are promising. These novel PLA thermoplastic composites with enhanced properties have potential for many applications, such as packaging materials, textiles, appliance components, autoparts, and medical implants.
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Li, Rui. "Plastic UV radiation protection operating by Stokes emission." Thesis, Brunel University, 2013. http://bura.brunel.ac.uk/handle/2438/12434.

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A range of inorganic nanoparticles/nanophosphors that act as ultraviolet radiation absorbers were characterised and assessed in this thesis. Iron doped lithium aluminate phosphor was synthesised using a solid state reaction and also by flame spray pyrolysis. The phosphors prepared by different synthesis methods were characterised to identify their crystal structures and morphologies. Downconverting photoluminescent properties of the phosphors both as pure powders and embedded in polypropylene by co-rotating twin screw extrusion are reported. Zinc oxide nanoparticles made by flame spray pyrolysis were also investigated. They were incorporated into polymers by means of three different approaches including co-rotating twin screw extrusion, spin coating and solvent casting. The resulted composite films were explored to understand the distribution of the zinc oxide nanoparticles. The transmittance and ultraviolet absorption of the nanocomposites were studied and are reported herein. Another set of nanophosphors studied were zinc rich luminescent zinc oxides. They were prepared from the zinc oxide nanoparticles by firing them in a reducing atmosphere. The as-prepared nanophosphors manifested good downconverting photoluminescent properties and maintained their functions when embedded into polystyrene by solvent casting. In this thesis a new route of synthesising aluminium doped zinc oxide nanoparticles was also established. This new approach was based on a series of unexpected results within some trials that were attempting to coat a layer of alumina on the zinc oxide nanoparticles. The concentration of the Al3+ in the final product could be adjusted by tailoring the amount of the Al3+ in the reactants during the synthesis procedures. It was also possible to coat various zinc oxide nanostructures with the aluminium doped zinc oxide.
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Musino, Dafne. "Impact of surface modification on the structure and dynamics of silica-polymer nanocomposites." Thesis, Montpellier, 2017. http://www.theses.fr/2017MONTS015/document.

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Les matériaux nanocomposites obtenus par la dispersion de charges nanométriques dans un polymère ont de nombreuses applications industrielles à cause de l’amélioration des propriétés des matrices. La dispersion des charges pendant le procès de préparation des nanocomposites est déterminée par les interactions entre charges et avec le polymère. L’état final de dispersion impacte les propriétés structurales, dynamiques et mécaniques du matériau.Dans ce travail de thèse, nous proposons l’étude de nanocomposites produits par dispersion de billes de silice hydrophiles dans une matrice de polymère hydrophobe, i.e., styrene-butadiene (SB), couramment utilisé dans les pneumatiques. Nous avons notamment étudié l’impact des agents de recouvrement - des silanes réagissant avec la surface des charges – qui sont utilisés afin de promouvoir la compatibilité entre la silice et le SB.Dans un premier temps, nous avons étudié des matériaux composites industriels simplifiés obtenus par l’incorporation de silice hautement dispersible dans le SB. En couplant des expériences de diffusion des rayons-X aux petits angles (DXPA) avec de la microscopie, nous avons montré que : i) la présence d’un catalyseur (DPG) amplifie l’effet de l’agent de recouvrement; ii) l'augmentation de la quantité de silane favorise la réduction de la taille des agrégats de silice. De plus, un système modèle équivalent au système industriel simplifié a été développé, mais avec une silice colloïdale. Nous avons mis au point une nouvelle méthode pour modifier la surface des billes de silice en suspensions dans en mélange eau/éthanol. Ces nanoparticules sont ensuite stabilisées dans le même solvant utilisé pour la dissolution du SB, le MEK. Enfin, le composite modèle est obtenu par évaporation du solvant. La dispersion des billes de silice greffées a été étudiée en suspension (i.e., dans le mélange eau/éthanol et MEK) et dans le nanocomposite, en couplant DXPA avec des simulations de Monte-Carlo inverse. Nous avons montré que la qualité de la dispersion dépend du type de silane utilisé et qu’elle est transférée du solvant (MEK) au composite. De plus, l’impact des agents de recouvrement sur les propriétés dynamiques (relaxation α) du système modèle a été étudié par spectroscopie diélectrique, BDS. Nous avons découvert que les agents de recouvrement peuvent plastifier le SB pur, en induisant une baisse significative de la température de transition vitreuse. Dans les composites, la modification de l’état de surface des billes par l’agent de recouvrement n’altère pas la relaxation α. Cependant, la présence de molécules de silane libres dans la matrice polymère du nanocomposite peut également induire un effet de plastification
Nanocomposite materials made by dispersion of nano-scale fillers in a soft polymer matrix attract industrial interest because of their enhanced properties. During their formulation, filler-filler and filler-polymer interactions affect the dispersion of the particles, and thus the final nanocomposite structure. The filler dispersion as well as dynamical properties control many material properties and in particular the mechanical response of these materials.In this PhD work, we propose the study of nanocomposites made by dispersion of nano-metric hydrophilic silica particles in a soft hydrophobic polymer matrix of styrene/butadiene (SB), which is commonly used in car tire manufacturing. Since coating agents can react with the filler surface tuning the silica-silica and the silica-polymer interactions, they have been used to promote the compatibility between silica and SB. Firstly, we investigate “simplified industrial nanocomposites” obtained by solid mixing of SB and millimetric silica pellets. By a multiscale approach (microscopy and X-ray scattering, SAXS) we show that: i) the presence of a catalyzer (DPG) unambiguously amplifies the action of the coating agent; ii) the increase of silane content induces the progressive decrease of silica aggregate size. The study of the simplified industrial nanocomposites has been extended to a silica/SB model system. We developed an efficient method to surface-modify colloidal silica NPs in ethanol/water, to stabilize them in the same solvent (MEK) used to dissolve the polymer, and to obtain the final model nanocomposite by solvent casting. For the structural characterization of this multi-step system, we propose a combined SAXS-reverse Monte Carlo approach which allows to investigate the dispersion state of surface-modified silica NPs in precursor solvents (i.e., ethanol/water and MEK) and in the polymer matrix. The filler dispersion is influenced by the characteristics of the grafted silane molecule (varying hydrophobicity, grafting function, and density) and it is shown the quality of the dispersion state is maintained from the precursor suspension to the nanocomposite. Moreover, Broadband Dielectric Spectroscopy (BDS) has been used to investigate the role of silane coating agents in the segmental dynamics of model nanocomposites. We show that the silane molecules can act as plasticizers in pure styrene-butadiene matrices, inducing a significant decrease of the glass transition temperature. We also prove that the chemical surface-modification of the fillers does not affect the segmental dynamics (α-relaxation) in nanocomposites, whereas the presence of “free” silane molecules in the polymer bulk can induce a detectable plasticization effect
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30

Julien, Tamalia. "Synthesis, Modification, Characterization and Processing of Molded and Electrospun Thermoplastic Polymer Composites and Nanocomposites." Scholar Commons, 2018. https://scholarcommons.usf.edu/etd/7631.

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This dissertation focuses on the versatility and integrity of a novel, ultrasoft polycarbonate polyurethane (PCPU) by the introduction of nanoparticles and lithium salts. Additionally, the research takes into account the use of electrospinning as a technique to create PCPU and polyimide (PI) fibers. These polymers are of interest as they offer a wide range of properties and uses within the medical and industrial fields. An industrial batch of an ultrasoft thermoplastic polyurethane (TPU) was synthesized using a two-step process. The first was to create an end capped pre-polymer from methylene bis (4-cyclohexylisocyanate), and a polycarbonate polyol made up of 1,6- hexanediol and 3-methyl-1,5-pentanediol. The second step was done by reacting the pre-polymer with an excess of the polycarbonate polyol with a chain extender, 1,4-butanediol. Biocompatibility testing such as USP Class VI, MEM Elution Cytotoxicity and Hemolysis toxicology reported that PCPU showed no toxicity. This novel type of polyurethane material targets growing markets of biocompatible polymers and has been used for peristaltic pump tubing, but also can be utilized as balloon catheters, enteral feeding tubes and medical equipment gaskets and seals. This material is ideal for replacing materials such as soft plastisols containing diethylhexyl phthalate for use in biomedical and industrial applications. After extensive characterization of this polymer system another dimension was added to this research. The addition of nanoparticles and nanofillers to polyurethane can express enhanced mechanical, thermal and adhesion properties. The incorporation of nanoparticles such as nanosilica, nanosilver and carbon black into polyurethane materials showed improved tensile strength, thermal performance and adhesion properties of the PCPU. Samples were characterized using contact angle measurements, Fourier transform spectroscopy (FTIR), differential scanning calorimetry (DSC), parallel plate rheology and tensile testing. The second chapter entails the fabrication and characterization of PCPU nanofibers and nanomembranes through a process known as electrospinning. The resulting PCPU nanomembranes showed a crystalline peak from the WAXS profile which is due to electrospun and solution strain induced crystallinity. The PCPU nanocomposite nanomembranes displayed increased thermal stability and an increase in tensile performance at higher weight percent. The nanomembranes were investigated using contact angle measurements, thermogravimetric analysis (TGA), DSC, WAXS, SAXS and tensile testing. The final chapter focuses on investigating the rheological properties of PCPU/lithium electrolytes as well as transforming an unprocessable polyimide powder into a nanomembrane. The PCPU/ lithium composite electrolyte showed an increase in the activation energy and conductivity, while the PI/lithium showed increased conductivity over time. Dynamic mechanical analysis and four-point probe was used to investigate the samples.
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31

Kaur, Jasmeet. "Properties of biologically relevant nanocomposites: effects of calcium phosphate nanoparticle attributes and biodegradable polymer morphology." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/33981.

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This research is directed toward understanding the effect of nanoparticle attributes and polymer morphology on the properties of the nanocomposites with analogous nanoparticle chemistry. In order to develop this understanding, polymer nanocomposites containing calcium phosphate nanoparticles of different specific surface areas and shapes were fabricated and characterized through thermal and thermomechanical techniques. Nanoparticles were synthesized using reverse microemulsion technique. For nanocomposites with different surface area particles, the mobility of amorphous polymer chains was restricted significantly by the presence of particles with an interphase network morphology at higher loadings. Composites fabricated with different crystallinity matrices showed that the dispersion characteristics and reinforcement behavior of nanoparticles were governed by the amount of amorphous polymer fraction available. The study conducted on the effect of nanoparticle shape with near-spherical and nanofiber nanoparticles illustrated that the crystallization kinetics and the final microstructure of the composites was a function of shape of the nanoparticles. The results of this research indicate that nanoparticle geometry and matrix morphology are important parameters to be considered in designing and characterizing the structure-property relationship in polymer nanocomposites.
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32

Glogowski, Elizabeth M. "Nanoparticle functionalization and grafting-from chemistry for controlling surface properties and nanocomposite behavior." Amherst, Mass. : University of Massachusetts Amherst, 2009. http://scholarworks.umass.edu/dissertations/AAI3349701/.

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Schlea, Michelle Renee. "Processing and characterization of high performance polyimide nanocomposites." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/39557.

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The goal of this work was to achieve a homogeneous morphology of carbon nanotubes in a polyimide matrix, characterize the resulting nanocomposite properties, and understand structure-property relationships. Melt-mixing was used as an effective method for dispersing multiwall nanotubes and carbon nanofibers in a phenylethynyl terminated imide resin where aggregation occurred only in particle-saturated systems. Particle network formation within the nanocomposites was studied using rheology and impedance spectroscopy; results showed that the electrical percolation threshold occurred at a lower particle loading than the rheological percolation threshold, consistent with the oligomer size in comparison to the distance for electrical conductivity (~5 nm). Thermomechanical analysis showed that the addition of nanoparticles enhanced the polyimide storage modulus and thermal behavior indicated that the nanoparticles restricted polymer motion to higher temperatures. A study of the cure mechanism of the oligomer with and without nanoparticles showed that the nanoparticles reduced the activation energy required for cure initiation while increasing the obtainable extent of cure at various isothermal temperatures. The work presented in this dissertation shows that an easy, time effective processing method can be used to homogeneously disperse nanoparticles in an imide oligomer, and the resulting nanocomposites exhibit enhanced properties. A business plan is also presented that reflects the market potential of this technology.
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Haba, D., M. Barbezat, and A. J. Brunner. "Secondary Crack Formation as Fracture Mechanism in Nanocomposites of Epoxy and Fullerene-Like WS2." Thesis, Sumy State University, 2015. http://essuir.sumdu.edu.ua/handle/123456789/42488.

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Fullerene-like WS2 (IF-WS2) nanoparticles (NPs) were used as a toughening agent in epoxy nanocomposites. Already 0.5 % IF-WS2 by mass increased the critical energy release rate GIc by 45 % to 62 %. Conicsection-shaped crack lines were observed on the fracture surfaces in some distance to the NPs. Nanomechanical AFM modulus measurements showed, however, no measurable differences between the modulus distribution in the vicinity of the NPs and the bulk epoxy. Possible secondary crack formation at the NPs explains the crack lines nicely. The crack line geometry allows determining the relative velocity of the secondary crack. Topographic AFM showed vertical steps several hundred nanometers high at the crack lines, indicating shear fracture and suggesting the presence of numerous subsurface cracks, which might explain the toughness increase.
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Capozzi, Charles J. "Controlled self-assembly of ito nanoparticles into aggregate wire structures in pmma-ito nanocomposites." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/28277.

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Thesis (M. S.)--Materials Science and Engineering, Georgia Institute of Technology, 2009.
Committee Chair: Gerhardt, Rosario; Engineering: Dr. Arun M. Gokhale; Engineering: Dr. Preet Singh; Engineering: Dr. Mohan Srinivasarao; Engineering: Dr. Meisha Shofner.
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Starkweather, Nathan S. "Controlling Nanoparticle Dispersion For Nanoscopic Self-Assembly." DigitalCommons@CalPoly, 2012. https://digitalcommons.calpoly.edu/theses/973.

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Nanotechnology is the manipulation of matter and devices on the nanometer scale. Below the critical dimension length of 100nm, materials begin to display vastly different properties than their macro- or micro- scale counterparts. The exotic properties of nanomaterials may trigger the start of a new technological revolution, similar to the electronics revolution of the late 20th century. Current applications of nanotechnology primarily make use of nanoparticles in bulk, often being made into composites or mixtures. While these materials have fantastic properties, organization of nano and microstructures of nanoparticles may allow the development of novel devices with many unique properties. By analogy, bulk copper may be used to form the alloys brass or bronze, which are useful materials, and have been used for thousands of years. Yet, organized arrays of copper allowed the development of printed circuit boards, a technology far more advanced than the mere use of copper as a bulk material. In the same way, organized assemblies of nanoparticles may offer technological possibilities far beyond our current understanding. In the first project, 1D assemblies of nanoparticles were explored. 1D anisotropic assemblies of nanoparticles are the simplest organized nanostructures which may be fabricated. One of the greatest difficulties in developing commercial products is in the transfer of a process from the laboratory to manufacturing scale. While many techniques may be used to develop 1D assemblies in lab, simple techniques are needed to allow the fabrication of these assemblies on a large, cost effective scale. Use of shear, shown previously to induce colloidal ordering in solutions, is a technique that may be readily adapted from the coatings industry as a process for forming 1D assemblies, if the optimal conditions can be found. Atomic force microscopy was used to study the role of shearing forces produced by drawdown and spraying application in the formation of 1D assemblies of nanoparticles. Formation of 1D strings was observed to increase with greater application of simple shear, but greater spraying forces were found to decrease formation of strings. This is explained in terms of greater simple shear providing a greater driving force for string formation, while greater spraying shear acted to irreversibly disperse the particles. The second project focused on the development of a learning module for education of students at various academic levels on the significance of the surface area of nanomaterials. This project was commissioned by the Global Waste Research Institute, a multidisciplinary organization based at Cal Poly, concerned with performing research and education in areas related to waste management, particularly of emerging waste streams. As nanotechnology and nanoparticles become more prevalent in consumer products and industrial processes, the volume of nanowaste is increasing rapidly. To address challenges associated with processing this unique form of waste, understanding of the fundamental processes controlling the unique properties of nanoparticles is necessary. A learning module was developed using a laboratory demonstration and video presentation to illustrate concepts related to differences in the properties between microparticles and nanoparticles. The laboratory demonstration was designed to be simple to understand, and quick, simple, and inexpensive to perform. The video presentation was designed to be a 15 minute presentation relating the concepts of nanotechnology, nanoparticles, surface area, and fundamental differences as compared to conventional materials. Dispersions of particles within aqueous media were used as a framework for the discussion, in a manner comprehensible by students ranging from 12th grade high school students to graduate students in relevant programs. The third and final project focused on self-assembly of particles in nematic liquid crystalline colloids. Dispersions of colloidal particles in liquid crystals (LCs) are a relatively new set of composite materials, host to a variety of interactions not seen in colloids in isotropic media. Presence of colloidal particles disrupts the local nematic director, resulting in a loss of long-range elastic energy. Interactions between particles and LC molecules results in dipolar or quadrupolar defects, depending on the nature of the interactions between particle and LC. The loss of long-range elastic energy can be minimized through aggregation of particles. The defects formed by interactions between particles and LC stabilize these aggregations as linear chains, either along the nematic director in the case of dipolar defects, or at an offset angle in the case of quadrupolar defects. Dispersions of silica microspheres in the nematic phase of a thermotropic liquid crystal were studied using polarizing light microscopy. Strong homeotropic anchoring was observed, indicated by the abundant formation of hedgehog defects. These defects were found to play a role in self-assembly of particles along the nematic director, resulting aggregates containing up to a dozen aligned particles. In addition, particles were observed to aggregate in chains along grain boundaries in the liquid crystal, acting to stabilize the high energy interface between different grain directions, an effect not previously reported in the scientific literature for nematic colloids.
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Pirner, Daniela [Verfasser], and Stephan [Akademischer Betreuer] Förster. "Controlled Preparation of Nanoparticles and Polymer Core-Shell Structures for Use in Organogels and Nanocomposites / Daniela Pirner ; Betreuer: Stephan Förster." Bayreuth : Universität Bayreuth, 2017. http://d-nb.info/1128226138/34.

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VU, YEN THI. "SYNTHESIS AND CHARACTERIZATION OF ELASTOMER-BASED COMPOSITES AND POLYMER-IMMOBILIZED COLLOIDAL TRANSITION METAL NANOPARTICLES: CATALYTIC SELECTIVITY AND MORPHOLOGY." University of Cincinnati / OhioLINK, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1004541836.

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39

Hancock, Matthew Logan. "THE FABRICATION AND CHARACTERIZATION OF METAL OXIDE NANOPARTICLES EMPLOYED IN ENVIRONMENTAL TOXICITY AND POLYMERIC NANOCOMPOSITE APPLICATIONS." UKnowledge, 2019. https://uknowledge.uky.edu/cme_etds/112.

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Ceria (cerium oxide) nanomaterials, or nanoceria, have commercial catalysis and energy storage applications. The cerium atoms on the surface of nanoceria can store or release oxygen, cycling between Ce3+ and Ce4+, and can therefore act as a therapeutic to relieve oxidative stress within living systems. Nanoceria dissolution is present in acidic environments in vivo. In order to accurately define the fate of nanoceria in vivo, nanoceria dissolution or stabilization is observed in vitro using acidic aqueous environments. Nanoceria stabilization is a known problem even during its synthesis; in fact, a carboxylic acid, citric acid, is used in many synthesis protocols. Citric acid adsorbs onto nanoceria surfaces, capping particle formation and creating stable dispersions with extended shelf lives. Nanoceria was shown to agglomerate in the presence of some carboxylic acids over a time scale of up to 30 weeks, and degraded in others, at pH 4.5 (representing that of phagolysosomes). Sixteen carboxylic acids were tested: citric, glutaric, tricarballylic, α-hydroxybutyric, β-hydroxybutyric, adipic, malic, acetic, pimelic, succinic, lactic, tartronic, isocitric, tartaric, dihydroxymalonic, and glyceric acid. Each acid was introduced as 0.11 M, into pH 4.5 iso-osmotic solutions. Controls such as ammonium nitrate, sodium nitrate, and water were also tested to assess their effects on nanoceria dissolution and stabilization. To further test stability, nanoceria suspensions were subject to light and dark milieu, simulating plant environments and biological systems, respectively. Light induced nanoceria agglomeration in some, but not all ligands, and is likely to be a result of UV irradiation. Light initiates free radicals generated from the ceria nanoparticles. Some of the ligands completely dissolved the nanoceria when exposed to light. Citric and malic acids form coordination complexes with cerium on the surface of the ceria nanoparticle that can inhibit agglomeration. This approach identifies key functional groups required to prevent nanoceria agglomeration. The impact of each ligand on nanoceria was analyzed and will ultimately describe the fate of nanoceria in vivo. In addition, simulated biological fluid (SBF) exposure can change nanoceria’s surface properties and biological activity. The citrate-coated nanoceria physicochemical properties such as size, morphology, crystallinity, surface elemental composition, and charge were determined before and after exposure to simulated lung, gastric, and intestinal fluids. SBF exposure resulted in either loss or overcoating of nanoceria’s surface citrate by some of the SBF components, greater nanoceria agglomeration, and small changes in the zeta potential. Nanocomposites are comprised of a polymer matrix embedded with nanoparticles. These nanoparticles can alter material and optical properties of the polymer. SR-399 (dipentaerythritol pentaacrylate) is a fast cure, low skin irritant monomer that contains five carbon-carbon double bonds (C=C). It is a hard, flexible polymer, and also resistant to abrasion. It can be used as a sealant, binder, coating, and as a paint additive. In this case, metal oxide nanoparticles were added to the monomer prior to polymerization. Titania nanoparticles are known to absorb UV light due to their photocatalytic nature. Titania nanoparticles were chosen due to their high stability, non-toxicity, and are relatively quick, easy, and inexpensive to manufacture. Channels in thin monomer films were created using a ferrofluid manipulated by magnetic fields. The mechanical properties of a microfluidic device by rapid photopolymerization is dependent on the crosslinking gradient observed throughout the depth of the film. Quantitative information regarding the degree of polymerization of thin film polymers polymerized by free radical polymerization through the application of UV light is crucial to estimate material properties. In general, less cure leads to more flexibility, and more cure leads to brittleness. The objective was to quantify the degree of polymerization to approximate the C=C concentration and directly relate it to the mechanical properties of the polymer. Polymerization of C=C groups was conducted using a photoinitiator and an UV light source from one surface of a thin film of a multifunctional monomer. The C=C fraction in the film was found to vary with film depth and UV light intensity. The extents of conversion and crosslinking estimates were compared to local mechanical moduli and optical properties. A mathematical model linking the mechanical properties to the degree of polymerization, C=C composition, as a function of film depth and light intensity was then developed. For a given amount of light energy, one can predict the hardness and modulus of elasticity. The correlation between the photopolymerization and the mechanical properties can be used to optimize the mechanical properties of thin films within the manufacturing and energy constraints, and should be scalable to other multifunctional monomer systems.
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Rahneshin, Vahid. "Versatile High Performance Photomechanical Actuators Based on Two-dimensional Nanomaterials." Digital WPI, 2018. https://digitalcommons.wpi.edu/etd-dissertations/549.

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The ability to convert photons into mechanical motion is of significant importance for many energy conversion and reconfigurable technologies. Establishing an optical-mechanical interface has been attempted since 1881; nevertheless, only few materials exist that can convert photons of different wavelengths into mechanical motion that is large enough for practical import. Recently, various nanomaterials including nanoparticles, nanowires, carbon nanotubes, and graphene have been used as photo-thermal agents in different polymer systems and triggered using near infrared (NIR) light for photo-thermal actuation. In general, most photomechanical actuators based on sp bonded carbon namely nanotube and graphene are triggered mainly using near infra-red light and they do not exhibit wavelength selectivity. Layered transition metal dichalcogenides (TMDs) provide intriguing opportunities to develop low cost, light and wavelength tunable stimuli responsive systems that are not possible with their conventional macroscopic counterparts. Compared to graphene, which is just a layer of carbon atoms and has no bandgap, TMDs are stacks of triple layers with transition metal layer between two chalcogen layers and they also possess an intrinsic bandgap. While the atoms within the layers are chemically bonded using covalent bonds, the triple layers can be mechanically/chemically exfoliated due to weak van der Waals bonding between the layers. Due to the large optical absorption in these materials, they are already being exploited for photocatalytic, photoluminescence, photo-transistors, and solar cell applications. The large breaking strength together with large band gap and strong light- matter interaction in these materials have resulted in plethora of investigation on electronic, optical and magnetic properties of such layered ultra-thin semiconductors. This dissertation will go in depth in the synthesis, characterization, development, and application of two- dimensional (2D) nanomaterials, with an emphasis on TMDs and molybdenum disulfide (MoS2), when used as photo-thermal agents in photoactuation technologies. It will present a new class of photo-thermal actuators based on TMDs and hyperelastic elastomers with large opto-mechanical energy conversion, and investigate the layer-dependent optoelectronics and light-matter interaction in these nanomaterials and nanocomposites. Different attributes of semiconductive nanoparticles will be studied through different applications, and the possibility of globally/locally engineering the bandgap of such nanomaterials, along with its consequent effect on optomechanical properties of photo thermal actuators will be investigated. Using liquid phase exfoliation in deionized water, inks based on 2D- materials will be developed, and inkjet printing of 2D materials will be utilized as an efficient method for fast fabrication of functional devices based on nanomaterials, such as paper-graphene-based photo actuators. The scalability, simplicity, biocompatibility, and fast fabrication characteristics of the inkjet printing of 2D materials along with its applicability to a variety of substrates such as plastics and papers can potentially be implemented to fabricate high-performance devices with countless applications in soft robotics, wearable technologies, flexible electronics and optoelectronics, bio- sensing, photovoltaics, artificial skins/muscles, transparent displays and photo-detectors.
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41

Nawaz, Sohail. "Preparation and long-term performance of poly(ethylene-co-butyl acrylate) nanocomposites and polyethylene." Doctoral thesis, KTH, Polymera material, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-104685.

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The current study discusses the preparation and long-term performance of polymer composites used for various purposes under different ageing conditions. The first part deals with the preparation and characterization of polymer nanocomposites based on poly(ethylene-co-butyl acrylate) (EBA–13 and EBA–28 with 13 and 28 wt % butyl acrylate, respectively) and 2–12 wt % (0.5–3 vol %) of aluminum oxide nanoparticles (two types with different specific surface areas and different hydroxyl-group concentrations; uncoated and coated with, respectively, octyltriethoxysilane and aminopropyltriethoxysilane). The nanocomposite with EBA–13 showed better overall nanoparticle dispersion while EBA–28 resulted in poor dispersion, probably due to insufficiently high shear forces acting during extrusion mixing which were unable to break down nanoparticle agglomerates. The activity of hindered phenolic antioxidant (0.2 wt%) in all EBA nanocomposites was assessed by determining the oxidation induction time using DSC. The composites containing uncoated aluminium oxide nanoparticles showed a much shorter initial OIT than the pristine polymer with the same initial concentration of antioxidant, indicating adsorption of antioxidant onto the nanoparticle surfaces. Composites containing coated nanoparticles showed a significantly smaller decrease in the initial OIT, suggesting the replacement of hydroxyl groups with organic silane tails, decreasing the concentration of available adsorption sites on the nanoparticle surfaces. The decrease in OIT with increasing ageing time in dry air at 90 °C of the nanocomposites was slower than that of the unfilled pristine polymer, suggesting a slow release of antioxidant from adsorption sites. The EBA nanocomposites exposed to liquid water at 90°C showed faster decrease of OIT than samples exposed to dry or humid air. The migration rate of antioxidant was controlled by the boundary conditions in the case of ageing in humid air and liquid water. The antioxidant diffusivity was lower for the composites containing uncoated ND than for the composites containing ND coated with octyltriethoxysilane or aminopropyltriethoxysilane. The migration and chemical consumption of deltamethrin DM, (synthetic pyrethroid) and synergist piperonyl butoxide from molded polyethylene sheets was also studied. Deltamethrin and piperonyl butoxide are often used for food  storage and insect control purposes. DM showed no signs of crystallization and remained in a liquid state after being cooled to room temperature. Exposure of polyethylene compound sheets to liquid water (at 80 & 95 °C), caused degradation and hydrolysis of the ester bond in the DM, present in the prepared material, and generated species containing hydroxyl groups. Liquid chromatography and infrared spectroscopy showed a significant migration of the active species in liquid water, whereas in air at 80 °C (60 and 80 %RH) the loss of DM and PBO was negligible over 30 days. The long-term performance of medium-density polyethylene stabilized with six different phenolic antioxidants (0.1 wt%) in aqueous chlorinated media at 70 °C was studied. The results were compared with data for previously studied solutions of antioxidants in squalane (a liquid, low molar mass analogue of polyethylene). A linear relationship was established between the time to reach antioxidant depletion in polyethylene tape samples and the time in squalane samples. Infrared spectroscopy and scanning electron microscopy of drawn samples revealed the onset of surface oxidation and surface embrittlement in tape samples exposed beyond the time for antioxidant depletion.

QC 20121109


Cable insulation materials
Loss of deltamethrin and pipronyl butoxide from polyethylene
long-term performance of polyethylene in chlorine dioxide water
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42

Repa, Kristen Lee Stojak. "Confinement Effects and Magnetic Interactions in Magnetic Nanostructures." Scholar Commons, 2016. http://scholarcommons.usf.edu/etd/6573.

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Multifunctional nanocomposites are promising for a variety of applications ranging from microwave devices to biomedicine. High demand exists for magnetically tunable nanocomposite materials. My thesis focuses on synthesis and characterization of novel nanomaterials such as polymer nanocomposites (PNCs) and multi-walled carbon nanotubes (MWCNTs) with magnetic nanoparticle (NP) fillers. Magnetite (Fe3O4) and cobalt ferrite (CoFe2O4) NPs with controlled shape, size, and crystallinity were successfully synthesized and used as PNC fillers in a commercial polymer provided by the Rogers Corporation and poly(vinylidene fluoride). Magnetic and microwave experiments were conducted under frequencies of 1-6 GHz in the presence of transverse external magnetic fields of up to 4.5 kOe. Experiments confirm strong magnetic field dependence across all samples. When incorporated in to a cavity resonator device, tangent losses were reduced, quality factor increased by 5.6 times, and tunability of the resonance frequency was demonstrated, regardless of NP-loading. Work on PNC materials revealed the importance of NP interactions in confined spaces and motivated the study of confinement effects of magnetic NPs in more controlled environments, such as MWCNTs with varying diameters. MWCNTs were synthesized with diameters of 60 nm, 100 nm, 250 nm, and 450 nm to contain magnetic NP fillers (~10 nm) consisting of ferrites of the form MFe2O4, where M = Co2+, Ni2+, or Fe2+. All confined samples exhibit superparamagnetic-like behavior with stronger magnetic response with respect to increasing MWCNT diameter up to 250 nm due to the enhancement of interparticle interactions. This thesis provides the first systematic study of this class of nanocomposites, which paves the way to inclusion of novel nanostructured materials in real-world applications.
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43

Wang, Xiaoteng. "Directed Nano-Patterning of Polymer Nanocomposite Thin Films." University of Akron / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1462141968.

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44

Matinise, Nolubabalo. "Electrolytic determination of phthalates organic pollutants with n nostructured titanium and iron oxides sensors." Thesis, University of the Western Cape, 2010. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_1177_1305892404.

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This work reports the chemical synthesis, characterisation and electrochemical application of titanium dioxide (TiO2) and iron oxide (Fe2O3) nanoparticles in the determination of phthalates. The other part of this work involved electrochemical polymerization of aniline doped with titanium and iron oxide nanoparticles for the sensor platform in the electrolytic determination of phthalates. The TiO2 and Fe2O3 nanoparticles were prepared by sol gel and hydrothermal methods respectively. Particle sizes of 20 nm (TiO2) and 50 nm (Fe2O3) were estimated from transmission electron microscopy (TEM) The other technical methods used in this study for the characterization of the TiO2 and iron oxide Fe2O3 NPs were SEM, XRD and UV- visible spectroscopy. Cyclic voltammetry, square wave voltammetry and electrochemical impedance spectroscopy (EIS) were used to study the electrochemical properties of the nanoparticles. These electrochemical studies of the nanoparticles were performed with a Fe2O3 or TiO2/nafion/glassy carbon membrane electrode in 0.1 M phosphate buffer (pH 7.0) and 0.1 M lithium perchlorate (pH 6.8) under an aerobic condition.

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45

Armas, Jeremy A. "Influence of High Aspect Ratio Nanoparticle Filler Addition on Piezoelectric Nanocomposites." DigitalCommons@CalPoly, 2018. https://digitalcommons.calpoly.edu/theses/2026.

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Piezoelectric nanogenerators (PNGs) are a new class of energy harvesting materials that show potential as a direct energy source for low powered electronics. Recently, piezoelectric polymers have been utilized for PNG technology due to low toxicity, high flexibility, and facile solution processing which provide manufacturing opportunities such as screen printing. Throughout the last decade, countless projects have focused on how to enhance the energy harvesting capabilities of these PNGs through the incorporation of nanoparticle fillers, which have been reported to enhance the piezoelectric properties of the film either directly through their intrinsic piezoelectric properties or through acting as surfaces for the interfacial nucleation of piezoelectric polymer crystals. Herein, two systems of PNGs formed from piezoelectric copolymers poly(vinylidene fluoride-co-hexafluropropylene) or poly(vinylidene fluoride-co-trifluoroethylene) mixed with high aspect ratio zinc oxide nanowires, hydroxyl functionalized multi-walled carbon nanotubes, or carboxylic acid functionalized single walled carbon nanotubes were investigated. Variations of filler type and loading are tested to determine influences on film morphology and piezoelectric properties. Power harvesting tests are conducted to directly determine the effect of nanoparticle addition on the output power of the non-poled devices. Both copolymer systems are found to exhibit a non-linear increase in output power with the increase of nanoparticle filler loading. The crystal polymorph properties of both systems are investigated by Fourier transform infrared spectroscopy. The microstructure of the poly(vinylidene fluoride-co-trifluoroethylene) films are further examined using X-ray diffraction, differential scanning calorimetry, polarized optical microscopy, and atomic force microscopy to determine the mechanism behind the increased power harvesting capabilities. As well, explanations for perceived output power from “self-poled” films are briefly explored.
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46

Tanja, Radusin. "Priprema i karakterizacija nanokompozita polimlečne kiseline i silicijum (IV) oksida namenjenog za pakovanje hrane." Phd thesis, Univerzitet u Novom Sadu, Tehnološki fakultet Novi Sad, 2015. http://www.cris.uns.ac.rs/record.jsf?recordId=94853&source=NDLTD&language=en.

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Poli(mlečna kiselina) (PLA) predstavlja jedan od najpopularnijih komercijalnih biorazgradivih polimera. Iako može da zameni neke od najčešće korišćenih sintetskih polimera, neka njegova svojstva (loša barijerna, termička i mehanička) još uvek predstavljaju prepreku u široj primeni, posebno za pakovanje hrane. Jedan od najsavremenijih načina prevazilaženja nedostataka u svojstvima biopolimera predstavljaju nanotehnologije.U ovom radu ispitan je uticaj dodatka različitih koncentracija hidrofobnih nanočestica silicijum (IV) oksida (od 0.2 mas.% do 5 mas.%) pripremom uzoraka u rastvoru, i rastopu na toplotna, mehanička, i barijerna svojstva PLA. Morfološke karakteristike uzoraka nanokompozita snimljene su pomoću skenirajuće elektronske mikroskopije (SEM). Ostvarena je izuzetno dobra disperzija i distribucija hidrofobnih čestica silicijum (IV) oksida koje su u malim udelima dodavane u poli(mlečnu kiselinu). Dobra disperzija i distribucija hidrofobnih čestica silicijum (IV) oksida ostvarena je kako pripremom nanokompozita metodom u rastvoru, tako i metodom u rastopu.Toplotna svojstva PLA i pripremljenih nanokompozita proučavana su primenom diferencijalnog skenirajućeg kalorimetra (DSC), dok je stepen kristalnosti određen rasipanjem X zraka pod širokim uglom(WAXD). Mehanička svojstva su ispitivana da bi se odredio uticaj dodatka nanočestica SiO2 na prekidnu čvrstoću i izduženje čistog PLA. Iako su prilikom pripreme materijala metodom u rastvoru, poboljšanja mehaničkih i barijernih svojstava postignuta pri udelima silicijum (IV) oksida u rasponu od 0,2 do 5 mas.%, najznačajnija poboljšanja postignuta su za najmanje udele nanočestica (0,2 mas.% i 0,5 mas.%). Poboljšanja mehaničkih i barijernih svojstava nanokompozita, primenjenih metodom u rastopu, su registrovana i za udele silicijum (IV) oksida od 0,2 do 3 mas.%.Takođe je ispitana mogućnost primene pripremljenog nanokompozita na osnovu poli(mlečne kiseline) i silicijum (IV) oksida za pakovanje prehrambenih proizvoda na primeru pakovanja svežeg svinjskog mesa (M. longissimus thoracis et lumborum). Ispitivanjem uticaja materijala za pakovanje svežeg mesa u vakuumu, na parametre tehnološkog (pH, boja), senzorskog, i mikrobiološkog kvaliteta mesa, utvrđeno je da su PLA kao i nanokompoziti na osnovu PLA sa različitim udelima silicijum (IV) oksida, pogodni za vakuum pakovanje i skladištenje svežeg svinjskog mesa.
Poly(lactic acid) presents one of the most popular bio-polymers for diverse applications. However, the use of PLA as food packaging material is limited due to poor barrier and mechanical properties. These properties could be improved by incorporation of nanoparticles into polymer matrix.In this work neat PLA films and PLA films with different percentage of hydrophobic fumed silica nanoparticles (0,2 wt.% to 5 wt.%) were prepared by solution casting and melt blending methods. Several procedures were used to characterize the influence of different silica content on dispersion (SEM), crystalline behavior (WAXD), thermal stability (DSC, TGA), mechanical and barrier properties. It is shown that the applied techniques and selection of specific hydrophobic spherical nanofiller provide a good dispersion and distribution of silica nanoparticles in poly(lactic acid) for both film preparation methods.Characteristics of films prepared by solution casting method showed improvements in mechanical and barrier properties for all loadings of nanofiller but the most significant improvements were achieved for lowest silica content (0,2 wt.% and 0,5 wt.%) The improvements in material characteristics (mechanical and barrier) for melt blending method were also achieved (for concentrations from 0,2 wt.% to 3 wt.%).After film preparation, selected cuts of M. longissimus thoracis et lumborum were packed in prepred films of polymer nanocomposites, and the shelf-life characterisation was conducted on technological, sensory and microbiological paramethers of quality. After shelf-life characterisation it can be concluded that polymer nanocomposites based on PLA and silica nanoparticles could be used for packaging od fresh pork meat in vacuum.
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47

Wozniak, A., A. Yegorov, and V. Ivanov. "Novel Polymer Nanocomposite with Silicon Carbide Nanoparticles." Thesis, Sumy State University, 2015. http://essuir.sumdu.edu.ua/handle/123456789/42514.

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Polyimides rank among the most heat-resistant polymers and are widely used in high temperature plastics, adhesives, dielectrics, photoresists, nonlinear optical materials, membrane materials for separation, and Langmuir–Blodgett (LB) films, among others. While there is a variety of high temperature polyimides, there is a demand for utilizing these materials at higher and higher temperatures in oxidizing and aggressive environments. Therefore, we sought to use materials which do not oxidize to enhance properties of the polyimide composition maintaining polyimide weights and processing advantages. In this paper we introduced results of utilizing inorganic nanostructured silicon carbide particles to produce an inorganic particle filled polyimide.
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48

Zinovyeva, Veronika. "Matériaux composés (polymères électroactif - nanoparticules de métal) et liquides ioniques." Thesis, Dijon, 2010. http://www.theses.fr/2010DIJOS056.

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La thèse de doctorat est consacrée aux synthèses de matériaux composites combinant des polymères conducteurs avec des métaux de transition, leur caractérisation par l'utilisation d'un ensemble des méthodes physiques, chimiques et électrochimiques et leur application catalytique. Ces processus ont été réalisés en milieu conventionnel (aqueux et organique) et dans les liquides ioniques à température ambiante. En tant qu’approche de synthèse, nous proposons une méthode simple qui consiste en la réduction chimique de sels inorganiques au moyen de l’oxydation du monomère en milieux variés. La polymérisation du pyrrole en utilisant des sels de Fe(III), Cu(II) et Pd(II) comme oxydants a été réalisée dans une large gamme de conditions de réaction. La cinétique du processus de polymérisation a été étudiée par spectrophotométrie UV-visible et DLS. Les matériaux obtenus ont été caractérisés par les méthodes de voltammétrie cyclique, analyse élémentaire, ICP-AES, AFM, SEM, EDX, TEM, XRD, XPS, XAS, IR. Les propriétés catalytiques et électrocatalytiques des matériaux nanocomposites Pd/polypyrrole ont été analysées pour des réactions du couplage direct hétéroaryle-aryle et l’électrooxidation de l’acide ascorbique. Les procédures alternatives de préparation de polymères conducteurs dans les liquides ioniques, en comparaison avec celles dans les solvents conventionnels, ont été décrites. L’influence des conditions de synthèse sur les propriétés électrochimiques et sur la morphologie des polymères conducteurs a été discutée. L’électrooxidation du ferrocène dans les liquides ioniques a été étudiée en détail, et le modèle du transport diffusionnel dans ces milieux visqueux a été proposé
The actual PhD thesis is devoted to syntheses of composite materials combining conducting polymers with transition metals, their characterization with the use of a large set of modern physical, chemical and electrochemical methods and initial studies of their catalytic applications. These processes were realized both in conventional (aqueous and organic) media and in room-temperature ionic liquids. As an approach for the chemical synthesis, a simple one-pot non-template method, consisting in the chemical reduction of various inorganic salts by pyrrole monomer in a set of solvents, was applied. Polymerization of pyrrole with the use of Fe(III), Cu(II) and Pd(II) salts as oxidants was carried out in a wide range of reaction conditions. The kinetics of the polymerization process was studied by UV-visible spectroscopy and DLS. The obtained materials were characterized by means of cyclic voltammetry, elemental CHNS analysis, ICP-AES, AFM, SEM, EDX, TEM, XRD, XPS, XAS, IR techniques. Catalytic and electrocatalytic properties of the synthesized Pd/polypyrrole nanocomposites were analyzed for the direct catalytic arylation of heteroaromatics and electrooxidation of ascorbic acid. Alternative ways to conducting polymer preparation in the form of films and powders inside ionic liquids, in comparison to those in conventional media, were described. The influence of the synthesis conditions and of the solvent nature on electrochemical properties and morphology of conducting polymers was discussed. The electrooxidation of ferrocene in ionic liquids was investigated in details, and a model for the diffusional transport in these viscous media was proposed
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49

Boday, Dylan Joseph. "SILICA AEROGEL-POLYMER NANOCOMPOSITES AND NEW NANOPARTICLE SYNTHESES." Diss., The University of Arizona, 2009. http://hdl.handle.net/10150/194891.

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Aerogels are extremely high surface area, low density materials with applications including thermal and acoustic insulators, radiation detectors and cometary dust particle traps. However, their low density and aggregate structure makes them extremely fragile and practically impossible to machine or handle without breaking. This has led to the development of aerogel composites with enhanced mechanical properties through the addition of polymers or surface modifiers. To date, attempts to strengthen aerogels have come with significant increases in density and processing time. Here I will describe our search for a solution to these problems with our invention using methyl cyanoacrylate chemical vapor deposition (CVD) to strengthen silica, aminated silica and bridged polysilsesquioxane aerogels. This approach led to a strength improvement of the composites within hours and the strongest composite prepared had a 100x strength improvement over the precursor aerogel. We also developed the first approach to control the molecular weight of the polymers that reinforce silica aerogels using surface-initiated atom transfer radical polymerization (SI-ATRP). Although PMMA reinforcement of silica aerogels improved the mechanical properties, further strength improvements were achieved by cross-linking the grafted PMMA. Additionally, we developed the first silica aerogels reinforced with polyaniline nanofibers that were strong and electrically conductive. Reinforcing silica aerogels with polyaniline allowed them to be used as a sensor for the detection of protonating and deprotonating gaseous species. Finally we developed a new approach for the synthesis of silica and bridged polysilsesquioxane spheres using a surfactant free synthesis. This approach allowed for the first in-situ incorporation of base sensitive functionalities during the sol-gel polymerization.
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50

TAWFILAS, MASSIMO. "Surface decoration of inorganic nanoparticles for novel polymer-based nanocomposite materials." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2019. http://hdl.handle.net/10281/241271.

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La decorazione superficiale è un metodo molto utile che permette di migliorare le prestazioni di materiali nanocompositi polimerici, in quanto agisce sull'incompatibilità tra la fase organica e quella inorganica. L'introduzione di un sottile strato polimerico consente una migliore dispersione di nanocristalli inorganici (NC) in matrici polimeriche, dove al contrario particelle nude aggregano e precipitano. Inoltre, la modifica superficiale è uno metodo efficace che permette di introdurre funzionalità aggiuntive ai NC, offrendo nuove proprietà per un gran numero di applicazioni. Durante il mio periodo di ricerca ho sintetizzato NC di biossido di titanio di diverse fasi e dimensioni e ho studiato il comportamento delle nanoparticelle in acqua con TD NMR. Abbiamo osservato che l'acqua interagisce con la superficie in modo tale da diventare una sonda in grado di identificare la fase cristallina del NC. In seguito, è stato condotto uno studio sul processo di grafting to su anatase sferico di polietilenossido monometiletere (mPEO) commerciale e polistirene (PS), sintetizzato tramite polimerizzazione RAFT. I polimeri sono stati modificati con diversi gruppi ancoranti. Gli esperimenti sono stati condotti utilizzando diversi solventi e condizioni sperimentali. Dal momento che abbiamo a che fare con un sistema composto da tre componenti, controllando le interazioni polimero-solvente, la reattività della superficie e l'interazione superficie-solvente, è stato possibile regolare la densità delle catene polimeriche legate e di conseguenza la loro conformazione. Successivamente è stata affrontata la preparazione di nanocompositi a base di poliuretano termoplastico (TPU) a partire da un sistema mixed double layer su anatase rodlike. È stata utilizzata una sintesi colloidale che si adatta alle esigenze di buon controllo sulla dimensione e sulla purezza del cristallo con la produzione su larga scala. Le particelle prodotte, ricoperte da acido oleico (OA), sono successivamente decorate con approccio grafting to utilizzando mPEO ad alto peso molecolare. Le nanoparticelle presentano uno strato ad alta densità di OA e uno a bassa densità di mPEO. In seguito, sono stati preparati per solvent catsing una serie di materiali nanocompositi basati su un double layer mPEO-OA@Anatase e single layer OA @ Anatase in TPU altamente alifatico. Sono stati ottenuti film otticamente trasparenti con indice di rifrazione più elevato (1.63) rispetto al TPU non caricato (1.49). Le prove meccaniche dei materiali nanocompositi hanno mostrato moduli elastici migliori rispetto al semplice TPU. In particolare, il mPEO-OA@Anatase, a parità di quantitativo di filler, ha mostrato un modulo elastico più elevato rispetto all’OA@Anatase. Infine, ho trascorso 7 mesi presso il gruppo del Dr. Benicewicz nella University of South Carolina (USA) in cui ho lavorato su un progetto focalizzato sulla sintesi di membrane polimeriche composte da materiale nanocomposito in grado di separare efficacemente miscele di gas. La prima parte del progetto è stata la preparazione di una serie di campioni basati su particelle di fumed silca (FS) utilizzando un approccio grafting-from con polimetilacrilato. In letteratura è riportato che nanocristalli graftati con polimeri, se in grado di riorganizzarsi ordinatamente nello spazio, possiedono migliori proprietà di permeabilità. Questo è legato al controllo sulla formazione di volume libero nel materiale. Si è osservato che le FS non sono in grado di riorganizzarsi ordinatamente e i dati sperimentali hanno confermato che questo sistema si comporta come una barriera fisica ai gas. Nella seconda parte del progetto è stata sintetizzato un nanocomposito con migliore permeabilità e selettività alla CO2. Questo materiale è stato ottenuto sfruttando la combinazione dell'effetto self-assembly, utilizzano NP di silice, e l'uso di un polimero più selettivo (metacrilammide con catena laterale oligoaniline) sintetizzato ad hoc.
Surface ligand engineering is an effective tool used to enhance polymer nanocomposites materials performance, since it plays a key role on one of the trickiest issues: the incompatibility between the organic and inorganic phase. The introduction of a thin polymeric layer enables a good dispersion of the inorganic nanocrystals (NCs) in polymer matrices, where otherwise bare particles aggregate and precipitate. The surface modification is an effective method to introduce additional functionalities to the NPs, giving new properties for a large number of applications. During my research I synthesized different titanium dioxide NCs of different phase and size. I investigated the behavior of bare TiO2 NCs in water. Taking advantage of the interaction between water molecules and titanium dioxide NCs, we found that water interacts in a way that make it a probe able to identify the titanium dioxide crystalline phase. Then an intensive study was done to understand the role of solvents during the grafting process in terms of interaction with polymer chains and inorganic surface. At first a study was done on the grafting-to process of polyethylene oxide monomethylether (mPEO) and polystyrene (PS) on spherical anatase NCs. Commercial mPEO of different molecular weight and polystyrene, synthesized via RAFT polymerization, were used and modified with different anchoring group. The polymers were grafted on anatase NCs through grafting-to approach using different solvents and experimental conditions. Water and methylene chloride were selected according to their ability to interact with the polymer chains and the NC’s surface. Thanks to this massive work we improved our knowledge on the grafting-to approach; we produced a method to create NCs with controlled graft densities and well-defined conformations. Thanks to our experience built during these years of research activity, we were able to prepare a nanocomposite material based on thermoplastic polyurethane (TPU). We started from a mixed double layer system tethered on rod-like anatase nanocrystal. The NCs covered with oleic acid (OA) were synthesized with a colloidal process and modified with a grafting-to approach using a high molecular weight mPEO. The as synthesized object is composed by a high density layer of OA and a low density layer of mPEO (mPEO-OA@Anatase). In order to investigate the properties of this type of objects, a set of nanocomposite materials based on mPEO-OA@Anatase and OA@Anatase were produced in a highly aliphatic TPU matrix with a solvent casting process. It was observed that for both mPEO-OA@Anatase and OA@Anatase optically clear films with improved refractive index (1.63) were obtained. The mechanical tests showed better elastic modulus for filler loaded nanocomposite materials. In particular the mPEO-OA@Anatase presented a higher elastic modulus than OA@Anatase when loaded with the same amount of nanofiller without affecting the optical properties. During my research period abroad, I spent 7 months at Dr. Benicewicz’s group in the University of South Carolina (USA). The aim of my project was focused on the synthesis of new nanocomposite material in the gas separation field. In the first part of the project we prepared a set of samples based on fumed silica (FS) particles using a grafting-from approach to modify the surface with RAFT polymerization. This kind of particles were not able to self-assemble in an organized and no improvement of the the gas permeation properties, even if FS were well dispersed into the polymer matrix. Experimental data confirmed that FS acts as a physical gas barrier. In the second part of the project were synthesized a nanocomposite material using the same approach on silica NP with polymethacrylamide with oligoaniline side chain. These NPs were able to self-assemble in a controlled fashion and thanks to a more selective polymer we obtained a material with enhanced permeability and selectivity to CO2.
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