Dissertations / Theses on the topic '030304 Physical Chemistry of Materials'
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O'Brien, Stephen. "The chemistry of mesoporous materials." Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390532.
Full textNgabe, Barnabe. "Physical chemistry of sulphide self-heating." Thesis, McGill University, 2014. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=123024.
Full textRESUMÉLa réalisation d'un modèle mathématique de l'auto-échauffement des concentrés sulfurés de nickel et de cuivre et des mélanges des minerais sulfurés, enjoint à la détermination des paramètres physico-chimiques tels que les capacités de chaleur spécifiques (Cp), et les énergies d'activation (Ea). Les capacités de chaleur spécifiques d'un concentré de cuivre et de trois concentrés de nickel contenant 6% d'humidité, ont été déterminées par utilisation d'un instrument de mesure de vitesse d'auto – échauffement et validées par la calorimétrie de chute dans l'intervalle de températures allant de 50 à 80oC. Les Cp (0.4 à 1.4 Jg-1K-1) obtenues sont similaires pour tous les échantillons. A partir des valeurs des Cp, les variations de l'enthalpie (ΔH), l'entropie (ΔS) et de l'énergie libre de Gibbs (ΔG) de l'auto échauffement ont été déterminées. La valeur négative de ΔG confirme le caractère spontané de l'auto échauffement des minerais sulfurés.Les énergies d'activation (Ea) pour l'auto-échauffement des concentrés de nickel et cuivre et des paires de minerais sulfurés étaient déterminées en faisant usage de l'appareil d'auto-échauffement. Les Ea ainsi obtenues oscillent entre 22 et 30 kJ.mol-1 : Ce qui est suggestif d'une rèaction chimique commune gouvernant l'auto-échauffement de ces matériaux. Ce fait est corroboré par la forte corrélation obtenue entre Ea et ln(QA/Cp) (Q (J.kg-1) est la chaleur de la rèaction chimique responsable de l'auto-échauffement et A (s-1) la constante d'Arrhenius).Ensuite celles-ci sont similaires à celle de l'oxydation partielle du H2S. Il se pourrait, ce faisant, que H2S soit un composé intermediaire lors de l'auto–échauffement des sulfures.Enfin, la corrélation positive entre Ea et la difference de potential (ΔV) dans les paires de minerais sulfurés et celle negative entre Cp et ΔV sont une preuve qu'il existe bel et bien une connection entre l'auto-échauffement et l'effet galvanique.
Frank, Robert A. "Physical chemistry of carbothermic reduction of alumina." Thesis, Massachusetts Institute of Technology, 1985. http://hdl.handle.net/1721.1/15150.
Full textMICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE
Vita.
Bibliography: leaves 177-180.
by Robert A. Frank.
M.S.
Tavener, P. "Electron spectroscopy of electrode materials." Thesis, University of Oxford, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.370304.
Full textYager, Kevin G. "Investigation of photomechanical surface patterning in azobenzene materials." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=103017.
Full textNeutron reflectometry was applied to measure in detail the photomechanical response of azobenzene materials. A significant photo-expansion effect, up to 17%, was observed at 25°C, attributed to the molecular free volume requirement of azo isomerization. Above a well-defined crossover temperature, which occurs at ~50°C for poly(disperse red 1 acrylate), the material response is inverted. At these elevated temperatures, photo-contraction effects, of more than -15%, were instead measured. In this case the combination of photo-induced motion and thermally-enabled mobility enables aggregation, aromatic stacking, and crystallization of the azobenzene dipoles. Using localized surface patterning experiments, it was confirmed that the mass transport phenomenon exhibits the same trend and phase relationship as the photomechanical effect. It is argued that the fundamental origin of surface mass transport in azo materials is in fact this newly identified photomechanical effect. This suggestion enables explanation of a variety of previously contradictory results in the literature.
Pope, Chris. "Hyroxylic polymers as materials for permanent holograms." Thesis, Cranfield University, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357054.
Full textRocheleau, Marie-Josée. "Investigation of membrane materials for solid-state, ion-selective electrodes." Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=74675.
Full textShaw, Christopher P. "Polymeric materials for piezoelectricity and second harmonic generation." Thesis, Cranfield University, 1991. http://dspace.lib.cranfield.ac.uk/handle/1826/3674.
Full textDennis, J. S. "The desulphurisation of flue gases using calcareous materials." Thesis, University of Cambridge, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372626.
Full textSimpson, W. Mark. "Solid state NMR studies of molecular crystalline materials." Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362006.
Full textFlora, Ware Howard. "Characterization and optimization of novel materials and interfaces in organic electronic devices." Diss., The University of Arizona, 2004. http://hdl.handle.net/10150/280511.
Full textLongwell, David James. "The application of new materials to ion-selective electrodes." Thesis, Queen's University Belfast, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334504.
Full textMollison, Neil Bruce. "Structural characterisation of amorphous materials by solid state NMR." Thesis, University of Kent, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.269106.
Full textGlarvey, Paul Anthony. "Synthesis and characterisation of novel conjugated liquid crystalline materials." Thesis, University of Sheffield, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.251250.
Full textMann, Sandra Elizabeth. "Studies of charge transfer in electrophotographic and related materials." Thesis, University of Exeter, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303920.
Full textSzablewski, M. "Multi-functional D-#pi#-A materials for molecular electronics." Thesis, Cranfield University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305322.
Full textTschaufeser, Petra. "Computer simulation studies of zeolites and related microporous materials." Thesis, University of Bath, 1992. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.306781.
Full textBengtsson, Katarina. "Additive manufacturing methods and materials for electrokinetic systems." Licentiate thesis, Linköpings universitet, Ytors Fysik och Kemi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-121252.
Full textIn the printed version the thesis number 1720 on the cover is incorrect. The correct thesis number is 1724 which is corrected in the electronic version.
Booth, Ryan Steven. "Experimental and theoretical studies on the decomposition mechanisms of geminal dinitro energetic materials." Thesis, The University of Chicago, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3615632.
Full textThese studies combine crossed laser-molecular beam scattering, velocity map imaging and computation to study the thermal decomposition mechanisms of geminal dinitro energetic materials. In our experimental studies, we photolytically generate two key intermediates in the decomposition of such energetic materials, 2-nitro-2-propyl radical and 2-nitropropene by photodissociating 2-bromo-2-nitropropane at 193 nm. These intermediates were produced at high internal energies and access a number of competing unimolecular dissociation channels. The scattering and imaging experiments provided evidence for four photodissociation pathways of 2-bromo-2-nitropropane along with a total of twelve subsequent dissociations of the resulting intermediate. In addition to the experimental studies, extensive calculations were conducted at the G4//B3LYP/6-311++g(3df,2p) level to compute the energetics of these dissociation events. Interestingly, a novel transition state (TS) for NO loss was discovered for the 2-nitro-2-propyl radical, which has a reaction barrier substantially lower than a traditional nitro-nitrite isomerization mechanism would suggest. This pathway is only available to nitroalkyl radicals and is extremely exothermic. To confirm the presence of this novel TS in a real-world system, the potential energy surface (PES) of a new energetic material, 1,1-diamino-2,2-dinitroethene (FOX-7), was calculated. This PES confirms the presence of the novel NO loss TS in FOX-7; this new TS allows for a low energy pathway to the production of NO in the unimolecular decomposition of FOX-7. In addition, these calculations demonstrate that initial loss of NO is competitive with simple C-N bond fission in unsaturated energetic materials. This low barrier and high exothermicity may be responsible for the extensive NO production and energy release observed in energetic materials with geminal dinitro groups.
Le, Baut Nicolas. "Physical and adhesive properties of some materials made by "click" chemistry." Access electronically, 2005. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20060712.161329/index.html.
Full textYau, Hon P. "Permeability of gases in copolymers, physical blends and composite particle materials." Thesis, Lancaster University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282409.
Full textAshton, Melanie. "The study of surface interactions of polymeric materials and related molecules." Thesis, University of Liverpool, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316462.
Full textJackson, Toby. "Synthesis, characterisation and analysis of triarylamines as potential charge transport materials." Thesis, University of Aberdeen, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.300957.
Full textHassen, J. H. "Spectroscopic analysis of adsorbed macrocyclic complexes on ceramic and related materials." Thesis, University of Essex, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.481601.
Full textChong, M. W. S. "Incorporation of spiropyran functionality into framework materials." Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/33949/.
Full textDartnell, Nicholas John. "Dry etching of silicon based semiconductor materials : plasma diagnostics and reaction mechanics." Thesis, University of Southampton, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239655.
Full textMcCleese, Christopher. "Femtosecond Time-Resolved Spectroscopy Studies of Interfacial Charge Separation Processes." Case Western Reserve University School of Graduate Studies / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=case149182204612303.
Full textRedeker, Neil. "MORPHOLOGY AND CONFORMATION OF POLYTHIOPHENE DERIVATIVES IN ANISOTROPIC CORE-SHELL NANOCOMPOSITES AND SOLUTION." DigitalCommons@CalPoly, 2013. https://digitalcommons.calpoly.edu/theses/1144.
Full textTerrones-Maldonado, Mauricio. "Production and characterisation of novel fullerene-related materials : nanotubes, nanofibres and giant fullerenes." Thesis, University of Sussex, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361404.
Full textStimson, Lorna M. "Phase behaviour of macromolecular liquid crystalline materials : computational studies at the molecular level." Thesis, Durham University, 2003. http://etheses.dur.ac.uk/3144/.
Full textRice, Craig R. "The synthesis of novel organic materials and the study of attractive intramolecular interactions." Thesis, University of Kent, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385089.
Full textAhmed, A. S. "Dispersions of chemical and natural materials to produce composites with commercially useful properties." Thesis, City University London, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375827.
Full textPerkins, Steven Patrick. "The effect of molecular structure on the mesogenic properties of liquid crystalline materials." Thesis, University of Southampton, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302348.
Full textPeters, Kyle C. "Sustainable Materials and Processes for Optoelectronic Applications." Case Western Reserve University School of Graduate Studies / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=case1554397264722736.
Full textHeadspith, David Andrew. "The preparation and characterisation of mixed-anion and non-oxide materials." Thesis, University of Hull, 2009. http://hydra.hull.ac.uk/resources/hull:2680.
Full textShepherd, Paul David. "The synthesis and possible non-linear optical second harmonic generation of some organosilicon materials." Thesis, University of Sussex, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385998.
Full textCross, Gregory John. "The synthesis and evaluation of highly polarisable organic materials for third-order nonlinear optical applications." Thesis, University of Hull, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363335.
Full textLee, Darren Frank. "The catalysed reactions of allyl alcohol using the microporous materials zeolite Y and TS-1." Thesis, University of Liverpool, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386828.
Full textBuley, Jill Marie. "The study of the dissolution and solubility kinetics of thin polymer films for resist materials." Thesis, University of Bath, 1993. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358772.
Full textPsarras, Peter Campbell. "Toward an Understanding of Methane Selectivity in the Fischer-Tröpsch Process." Cleveland State University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=csu1407953187.
Full textSacco, Amanda C. "An Extensive Study of Soft Materials Containing Carboxylic Acid Moieties to Determine Hydrogen Bond Energies Using Analytical and Theoretical Methods." Youngstown State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1442486805.
Full textDebnath, Sudeep. "Surface/Geochemistry of Iron and Manganese Oxide Nano-Materials in the Environment." Diss., Temple University Libraries, 2009. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/30879.
Full textPh.D.
Nanomaterials possess physical and chemical properties that may benefit medicine, catalysis, and environmental remediation. Apart from understanding the structure of nanomaterials, significant amount of research has focused on understanding the structural properties of nanoparticles that lead to their unique reactivity. Ferric hydroxides are important mineral components and the subject of much scientific research in environmental and soil sciences because of their ubiquity in soil, ground water and aquatic sediments Iron oxide nanoparticles found in the environment exhibit size-dependent behavior. Iron oxides also play an important role in environmental chemistry. Ferrihydrite is an important iron oxide mineral as they exist in most of the sediment environment, necessary precursors for more stable iron oxides like hematite. Iron oxides are also important in many living organisms and stored as protein-encapsulated iron(III) oxyhydroxide nanoparticles. Because of the ubiquitous nature of ferrihydrite in soil and sediments, understanding correlation between the surface reactivity and the structure, phase of ferrihydrite ie. homogeneous or heterogeneous phase dependent reaction is important from environmental point of view. Iron oxides also play an important role in atmospheric chemistry and size dependent surface catalytic properties towards atmospheric gases. Green house gases are frequently generated during the burning of fossil fuels in factories and power plants, or derived from natural processes such as volcanic eruptions. Both natural and engineered metal oxides have been utilized as catalysts or sorbents for removal or minimization of green house emissions. In an attempt to understand the structure and reactivity relationship, we have presented ferrihydrite dissolution under reducing conditions and in situ kinetic studies were performed on isolated individual single particles of ferrihydrite using AFM. Bulk batch studies are also presented, where particles exist as agglomerates. Interface dissolution reaction has been characterized with FTIR and results were confirmed with theoretical calculations. Normalized dissolution rate of individual ferrihydrite particle sheds light on the phase behavior of this material. This study indicates that the ferrihydrite is uniform in composition and supports the Michel et al model. The size-dependent reactivity of ferrihydrite toward the environmentally important gas sulfur dioxide SO2 was also studied as atmospheric emission of SO2(g) affects the environment because it promotes the production of acid rain. In this investigation, nano-ferrihydrite particles were synthesized with a narrow size distribution. The surface chemistry and reactivity (SO2(g) sorption) was studied with attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy in combination with molecular orbital/density functional theory (MO/DFT) frequency calculations. Results showed that SO2(g) sorption may be a sensitive function of the structural properties and size of the nanoparticles. Like Iron oxides, Manganese oxides also play a distinctive role in superficial soil or near surface environments. Birnessite is one of the most commonly occurring manganese oxides in the soils and sediments. Birnessite are known to provide a suitable surface for heterogeneous oxidation of As(III) to As(V), and thus contribute to the environmental fate of arsenic species in soil and sediments. In the present study we have made an effort to understand this fundamental geochemistry occurring at birnessite surface at the molecular scale using advanced surface sensitive tools like AFM and spectroscopic techniques like FTIR and XPS. Nano size manganese oxide was also prepared via biological routes. Nano-size manganese oxide was prepared using ferritin protein as the biological precursor. Solution phase arsenic oxidation studies were performed with Ferritin Manganese oxide. Ion chromatography is performed to investigate oxidation of As(III) and reduction of manganese, along with XPS analysis to monitor the oxidation states of arsenic and manganese species. Results were also verified with FTIR spectroscopy for interface speciation.
Temple University--Theses
Alkaabi, Khalifa. "The synthesis, chemical and physical characterisation of selected energetic binder systems." Thesis, Stellenbosch : University of Stellenbosch, 2009. http://hdl.handle.net/10019.1/1080.
Full textDue to numerous accidents involving munitions, recent interest has focused on the development and use of insensitive munitions (IM). Polymeric materials are used in insensitive munitions as binders or plasticizers. Most of the polymeric binders used are based on polycondensation reaction via using urethane linkages. The main aim of this study was the synthesis and characterization of selected energetic thermoplastic elastomers binder based on utilizing controlled free radical polymerization. This was achieved by using hydroxyl terminated poly (epichlorohydrin) (PECH-diol) and hydroxyl terminated glycidyl azide polymer (GAP-diol) as starting materials, and the subsequent synthesis of different macroinitiators. These macro-initiators were used to polymerize methyl methacrylate (MMA) to obtain thermoplastic elastomers. PECH-diol was prepared by cationic ring-opening polymerization (CROP) based on using borontrifluoride etherate (BF3-etherate) as catalyst and a low molecular weight diol as initiator. GAP-diol was synthesized by the reaction of PECH-diol with sodium azide in organic solvent.. Poly(epichlorohydrin-methyl methacrylate) (PECH-PMMA) and poly(glycidyl azidemethyl methacrylate) (GAP-PMMA) block copolymers were prepared by free radical polymerization of MMA monomer in presence of PECH and GAP macro-azoinitiator (MAI). The MAIs were prepared by the polycondensation reaction of hydroxyl terminated groups of elastomer with 4,4' azobis (4-cyanopentanoyl chloride) (ACPC). The phase behavior of blends of amorphous PMMA/PECH-diol and PMMA/GAP-diol was also investigated. Poly(epichlorohydrin-methyl methacrylate) (PECH-PMMA) and poly(glycidyl azidemethyl methacrylate) (GAP-PMMA) graft copolymers were synthesized by photopolymerization of MMA in presence of PECH and GAP with pendant N,Ndiethyldithiocarbamate groups as macro-photoiniferters. . Photopolymerization of MMA proceeded in a controlled fashion. A macro RAFT agent, based on the reaction of PECH with pendent dithiobenzoate was prepared. The macro-RAFT agent was used in the controlled thermal bulk polymerization of methyl methacrylate. Finally, living/controlled radical polymerization of MMA with four different photoiniferters, namely benzyl diethyl dithiocarbamate (BDC), 2-(N,N-diethyldithiocarbamyl) propionic acid (PDC), 2-(N,Ndiethyldithiocarbamyl) isobutyric acid (DTCA), and diethyl dithiocarbamateepichlorohydrin was achieved.
Lin, Andrew. "Metal-Organic Frameworks and Graphene-Based Support Materials for Heterogeneous Catalysis." VCU Scholars Compass, 2018. https://scholarscompass.vcu.edu/etd/5574.
Full textKanigan, Tanya. "Integrated optics spectroscopy of polymer thin films." Thesis, McGill University, 1995. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=40157.
Full textWaveguide Raman spectra indicate partial alignment of CA chains within the plane of the film. Deacetylation of CA films in aqueous ammonia to form glassy regenerated cellulose (RC) waveguides preserves orientational anisotropy of the parent CA film. Refractive index profiles are reconstructed from measured optical propagation constants of CA, RC and partially regenerated CA waveguides using inverse Wentzel-Kramers-Brillouin approximation methods. Partially regenerated CA films possess an asymmetric reflective index gradient attributed to depth inhomogeneity present in CA films prior to regeneration.
The effects of deviations from right angle scattering geometry on polarized waveguide Raman spectra are discussed. Polarization mode conversion is attributed to the presence of off-diagonal elements in the film dielectric tensor. In CA films, these off-diagonal elements result from excessive pressure on the coupling prism and partial orientation of polymer chains. Coupled mode theory is used to predict the effects of polarization mode conversion on the polarized Raman spectra as a function of film parameters and coupling angle.
Photoinduced birefringence and photoalignment are observed in ORMOSIL sol-gel films after exposure to guided light from an argon ion laser (514.5 nm and 488.0 nm lines). By simultaneously exciting TE and TM modes, non-transient, reversible off-diagonal dielectric tensor elements are introduced in the film. These off-diagonal elements cause coupling between the orthogonal TE and TM modes, which is, in turn, observed in polarized waveguide Raman spectra collected from the film. Photorefractive effects are attributed to photoinduced anisotropy (PIA) and glass photosensitivity phenomenon previously observed (by others) in doped silicate glasses.
Donakowski, Martin Daniel. "Syntheses, Local Environments, and Structure-Property Relationships of Solid- State Vanadium Oxide-Fluorides." Thesis, Northwestern University, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3615500.
Full textVanadium oxide-fluorides can exhibit properties of piezoelectricity, second harmonic generation (SHG) activity, electrochemical activity, and other phenomena. The first two properties derive from the second-order and Jahn-Teller distortions, respectively, of d0 and d1 vanadium; the electrochemistry derives from the reduction of VV to V IV,III,II.
An examination of the immediate environment of a vanadium cation facilitates an understanding of how a cation influences the structure of a compound and its resulting properties. In the inorganic hydrate CuVOF4(H 2O)7, the CuVOF4(H2O)6 basic-building unit (BBU) has a Λ-shape that compels polar packing in a structure that has SHG properties. The compound is a very rare example of a carbonless, SHG-active molecular crystal. Influences for its packing are reasoned with principles previously used within organic molecular crystallography.
The early transition metals (ETMs) of vanadium, niobium, and molybdenum within compounds of formulae K10(M2OnF 11-n)X (M = VV, NbV, n = 2, M = Mo VI, n = 4; X = halide) show a related packing motif of Λ-shaped BBUs in different structures. Owing to the absence or presence of Λ-shaped BBUs, these heterotypical structures crystallize decidedly into SHG-inactive or SHG-active forms when M = VV or M = NbV, MoVI, respectively. The future use and development of Λ-shaped BBUs within solid-state systems can result in SHG-active materials.
The material CuVOF4(H2O)7 presents an interesting coordination: the late transition metal (LTM, CuII) coordinates solely to the oxide anion of the vanadyl cation owing to hard-soft acid-base (HSAB) properties. The materials Na2[M(H2O) 2][V2O4F6] (MII = Co, Ni, Cu) show the LTM coordinates solely to the oxide anions of the V V cation while the alkali cation (NaI) coordinates solely to the fluoride anions. These HSAB properties were used to generate layers of hard or soft cation/anion rich regions in the electrochemically-active double wolframite AgNa(VO2F2)2.
These structure-property examinations of solid state vanadium oxide-fluorides are presented as principles for (i) fundamental understanding of ETM and BBU crystallographic environments, (ii) materials discovery for fundamental investigations, (iii) materials design, and (iv) materials for use in SHG, piezoelectric, and electrochemical processes.
Zaker, Yeakub. "Facile Size Focusing Synthesis of Silver Nanoparticles Capped with Aliphatic Thiol Ligands." University of Toledo / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1480456850511426.
Full textMadathingal, Rajesh Raman. "Nanoscale confinement and interfacial effects on the dynamics and glass transition/crystallinity of thin adsorbed films on silica nanoparticles." Diss., Temple University Libraries, 2011. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/116348.
Full textPh.D.
The research investigated in this dissertation has focused on understanding the structure-property-function relationships of polymer nanocomposites. The properties of composite systems are dictated by the properties of their components, typically fillers in a polymer matrix. In nanocomposites, the polymer near an interface has significantly different properties compared with the bulk polymer, and the contribution of the adsorbed polymer to composite properties becomes increasingly important as the filler size decreases. Despite many reports of highly favorable properties, the behavior of polymer nanocomposites is not generally predictable, and thus requires a better understanding of the interfacial region. The ability to tailor the filler/matrix interaction and an understanding of the impact of the interface on macroscopic properties are keys in the design of nanocomposite properties. In this original work the surface of silica nanoparticles was tailored by: a) Changing the number of sites for polymer attachment by varying the surface silanols and, b) By varying the size/curvature of nanoparticles. The effect of surface tailoring on the dynamic properties after the adsorption of two model polymers, amorphous polymethyl methacrylate (PMMA) and semicrystalline polyethylene oxide (PEO) was observed. The interphase layer of polymers adsorbed to silica surfaces is affected by the surface silanol density as well as the relative size of the polymer compared with the size of the adsorbing substrate. The non-equilibrium adsorption of PMMA onto individual colloidal Stöber silica (SiO2) particles, where Rparticle (100nm) > RPMMA (~6.5nm) was compared with the adsorption onto fumed silica, where Rparticle (7nm) ~ RPMMA (6.5nm) < Aggregate (~1000nm), both as a function of silanol density [SiOH] and hydrophobility. In the former case, TEM images showed that the PMMA adsorbed onto individual nanoparticles, so that the number of PMMA chains/bead could be calculated, whereas in the latter case bridging of PMMA between aggregates occurred. The anchoring point densities were comparable to the silanol densities, suggesting that PMMA adsorbed as trains rather than loops. For hydrophilic SiO2, Tg increased with [SiOH], as more carbonyl groups hydrogen bonded to the silanols, and was independent of particle morphology. For methylated silica, (CH3)3-SiO2, the adsorption isotherms were identical for colloidal and fumed silica, but Tg was depressed for the former, and comparable to the bulk value for the latter. The increased Tg of PMMA adsorbed onto fumed (CH3)3-SiO2 was attributed to the larger loops formed by the bridging PMMA chains between the silica aggregates. For nanocomposites the interphase region becomes more important as the surface/volume ratio of the nanoparticles increases. Polymers have chain dimensions (characterized by the radius of gyration, Rg) similar to the nanoparticles (Rnanoparticle) themselves, so that chain conformation, mobility and crystallinity can be affected by Rg/Rnanoparticle. Here, both the glass transition temperature (Tg) and degree of crystallinity (Xc) of polyethylene oxide (PEO) on individual SiO2 nanoparticles of nominal 15, 50 and 100 nm diameter (2 RSiO2) , in which Rg (PEO) was greater, equal to or less than RSiO2 was investigated. Plateau adsorption of PEO on SiO2 nanoparticles (PEO-SiO2) increased in the order PEO-SiO2 (100 nm) > PEO-SiO2 (50 nm) > PEO-SiO2 (15 nm). At plateau adsorption after melting and solidification, the samples were completely amorphous. The Tg of the adsorbed PEO increased in the order PEO-SiO2 (100 nm) > PEO-SiO2 (50 nm) > PEO-SiO2 (15 nm); since the Tgs were above 25oC in all cases, the PEO behaved more like a brittle solid than an elastomer. For comparable amounts of PEO that were adsorbed from solution but not melted, the melt endotherm increased in the order PEO-SiO2 (15 nm) > PEO-SiO2 (50 nm) > PEO-SiO2 (100 nm). These trends were interpreted as due to an increase in loop/tail lengths and thus flexibility, with a concomitant ability to crystallize, as Rg (PEO)/RSiO2 decreased and which was the result of less hydrogen bond formation between the oxygens of PEO and the silanols (SiOH) of the SiO2 as the nanoparticle size decreased. This in turn was attributed to the energetically unfavorable conformations necessary for the PEO chains to adopt in order to hydrogen bond with silanols on the smaller nanoparticles. The degradation behavior of amorphous PMMA and semicrystalline PEO on silica (SiO2) nanoparticles as a function of silanol density and nanoparticle size was investigated by derivative thermogravimetric analysis (DTGA) for adsorption amounts below plateau adsorption. For PMMA Td decreased as the number of SiOH/C=O contacts decreased, either from heat treatment of the SiO2, which reduced the silanol density, or as the nanoparticle size decreased, reducing the numbers of places that the PMMA chain contacted the nanoparticles.
Temple University--Theses
Gao, Ruixuan. "Designing Novel Semiconductor Nanowire Structures: Synthesis and Fabrication for Localized Photodetection and Sensing." Thesis, Harvard University, 2015. http://nrs.harvard.edu/urn-3:HUL.InstRepos:17463963.
Full textChemistry and Chemical Biology
Day, Robert Watson. "Crystal Growth on One-Dimensional Substrates: Plateau-Rayleigh Crystal Growth and Other Opportunities for Core/Shell Nanowire Synthesis." Thesis, Harvard University, 2015. http://nrs.harvard.edu/urn-3:HUL.InstRepos:17464133.
Full textChemistry and Chemical Biology