Thèses sur le sujet « Development of Polymers »

Thesis (MSc)--Stellenbosch University, 2002.
ENGLISH ABSTRACT: Multimedia was the buzzword of the previous decade. Electronic learning is the buzzword of this decade. Both concepts changed, and are still changing the way educators present knowledge and information to students, both locally and worldwide. South Africa, also standing in the midst of these technological changes, has its own unique opportunities regarding the teaching environment. Different factors are currently changing the educational scene in South Africa. With Curriculum 2000 and the Outcome-Based Education concept (OBE) came the opportunity to choose and incorporate relevant science and technology programmes into school curriculums. The introduction of Technology as a subject in junior secondary school, opened the door to bring students in contact with, for example, the vast world of material science. Senior secondary students, on the contrary, have little or no exposure to teaching programmes on modern materials; materials that rule their lives! There is a need for high quality, easily accessible and informative material science programmes. This provided the initiative to create this programme. Depending on the standard of students, "Fun with Polymers" can be used as: • a lecturing tool for teachers and lecturers • an encyclopeadia which students can interactively navigate to learn more about polymer science • a source of information to anyone curious about the interesting world of plastic materials. The name "Fun with Polymers" indicates that learning science can be fun (after ali!). The programme contains easy to use navigation buttons, helpfiles, hypertext, sound, animations and pictures to teach synthetic polymer material science. Content consists of the history of the development of polymer materials, basic polymer chemistry principles, information on the building of macromolecules, facts on synthetic polymer materials, and some questions and answers to test the student's knowledge. Practical experiments, with plastic materials, complement the theoretical information and provide students with hands-on experience.
AFRIKAANSE OPSOMMING: Multimedia was die gonswoord van die vorige dekade. Elektroniese leer is die gonswoord van die nuwe dekade. Beide hierdie konsepte het, en is nog steeds besig, om die wyse hoe kennis en inligting, plaaslik en wêreldwyd, aan studente oorgedra word, te verander. Suid-Afrika, as deel van hierdie tegnologiese veranderinge, bied unieke en uitdagende geleenthede op die gebied van onderwys. Verskillende faktore beïnvloed, op die oomblik, die plaaslike onderwys scenario. Die koms van Kurrikulum 2000 en Uitkomsgebaseerde Onderwys het die deur vir toepaslike wetenskap- en tegnologie programme, as deel van skoolleerplanne, geopen. Die toevoeging van Tegnologie, as vakgebied, tot die junior sekondêre fase, skep die geleentheid om studente in aanraking te bring met, byvoorbeeld, die enorme wêreld van materiaalkunde. Senior sekondêre studente het egter min tot geen blootstelling aan materiaalkunde leerprogramme ten spyte van die feit dat hul lewens daagliks deur moderne materiale beïnvloed en beheer word! Daar bestaan 'n behoefte aan hoë kwaliteit, maklik bekombare inligting oor moderne materiale en vandaar die dryfveer om hierdie program te skep. Afhangende van die standaard van die studente, kan hierdie program gebruik word as: • 'n onderrigprogram vir onderwysers en lektore • 'n bron van inligting wat studente interaktief kan navigeer om meer van polimeeerchemie te wete te kom • 'n bron van inligting vir enigiemand wat nuuskierig is oor die interessante wêreld van plastieke. Die naam van hierdie program: "Fun with Polymers" dui daarop dat die wetenskapleerproses pret kan wees! Die program bestaan uit maklik navigeerbare instruksies, hulplêers, hiperteks, klank, animasies, en foto's om lig te werp op die onderwerp van plastiek. Die inhoud beslaan die geskiedenis van die ontwikkeling van plastiek= materiale, basiese polimeerchemie beginsels, inligting oor die vorming van makro= molekules, feite oor sintetiese polimeermateriale, en vrae en antwoorde om die gebruiker te toets oor sy/haar kennis. Maklik uitvoerbare en toepaslike praktiese eksperimente komplimenteer die teoretiese inhoud van die multimedia program.

Kyoto University (京都大学)
0048
新制・課程博士
博士(工学)
甲第14643号
工博第3111号
新制||工||1463(附属図書館)
26995
UT51-2009-D355
京都大学大学院工学研究科高分子化学専攻
(主査)教授 澤本 光男, 教授 伊藤 紳三郎, 教授 辻 康之
学位規則第4条第1項該当

Comme je suis particulièrement intéressé par les nanosciences et les nombreuses applications des nanotechnologies, je me suis penché sur le développement de méthodes de fabrication de nanoparticules ultra-petites dont les fonctions peuvent être ajustées avec précision. Récemment, une nouvelle technologie appelée « technologie d’une seule chaîne », c’est-à-dire qui utilise une seule chaîne polymère, est devenue un sujet de recherche de plus en plus motivant pour la communauté scientifique. Cette technologie a l’avantage de dépendre d’une méthode facile de préparation de nanoparticules polymères d’une seule chaîne (SCNPs) et ayant des dimensions typiques de 1,5 à 20 nm. Leurs tailles ultra petites leur confèrent des propriétés spécifiques, ce qui permet de les utiliser comme capteurs, systèmes catalytiques, revêtements à faible viscosité, nanoréacteurs ou pour des applications biomédicales. Grâce aux contributions de nombreux scientifiques durant la dernière décennie, les méthodes de synthèse des SCNPs sont devenues très variées et représentent une technologie désormais mature. Néanmoins, de nombreux problèmes sont à résoudre dans ce domaine, ce qui permettra d’ajouter de nouvelles fonctions ou de les valoriser pour de nouvelles applications. Les polymères sensibles à plusieurs stimuli sont une classe de matériaux intelligents dont les propriétés peuvent être modifiées par l’application d’un stimulus extérieur. Ils sont utilisés extensivement dans les domaines énergétique et biomédical. Comme leurs propriétés physiques et chimiques peuvent être modifiées aisément et efficacement par un contrôle de leur environnement externe, ces polymères sont des candidats pour fabriquer de nouvelles SCNPs. Dans cette thèse, nous nous sommes intéressés au développement de SCNPs ayant de multiples fonctionnalités car cela permet d’ouvrir la voie pour de nouvelles applications. Pour cela, de nombreux polymères sensibles à plusieurs stimuli ont été préparés comme précurseurs à des SCNPs. En concevant spécifiquement ces polymères, il fut possible d’ajouter leurs propriétés de réponse à des stimuli dans les systèmes SCNPs. Le cœur même de cette thèse consiste en trois projets qui utilisèrent trois classes de SCNPs provenant de polymères sensibles aux stimuli. Grâce à leur réponse à plusieurs stimuli, ces SCNPs remplirent de nombreuses fonctions et subirent des modifications soit de leur structure, soit de leur morphologie, soit de leurs propriétés. Et en plus de la variété de fonctions, chaque classe de SCNPs a le potentiel pour de nombreuses applications. Dans la première étude présentée dans cette thèse (chapitre 1), nous avons préparé une classe de SCNPs photodégradables ayant une taille ajustable et inférieure à 10 nm. Il s’agit de polyesters rendus photosensibles par la présence de coumarines à l’intérieur de la chaîne principale (nommés CAPPG) grâce à la copolymérisation de coumarine diol, d’acide adipique et de propylène glycol (PPG). Cette incorporation de coumarines dans la chaîne principale permet au polymère d’être photosensible par deux façons. En effet, les coumarines peuvent se photo-dimériser, lorsqu’elles sont irradiées par des rayonnements UV (> 320 nm) en des cyclobutanes qui peuvent être ouverts à nouveau par d’autres rayonnements UV (254 nm) permettant la restauration des coumarines initiales. Cela a permis la création de SCNPs de tailles inférieures à 10 nm et incluant des propriétés de photodégradation. Cette propriété a été démontrée par une irradiation de 3 h avec des chaînes polymères de 13220 g/mol à 1385 g/mol dans les SCNPs. La taille de ces SNCPs (caractérisée par leur rayon hydrodynamique) peut être modifiée entre 3 nm et 5,3 nm en modifiant le taux de dimérisation des coumarines, ce qui est aisément obtenu en ajustant le temps d’irradiation UV. Les résultats ont démontré que cette méthode permet un contrôle aisé de la taille des SCNPs sans avoir recours à la synthèse de nombreux polymères précurseurs. Finalement, comme le polyester était biodégradable et biocompatible, ces SCNPs peuvent être exploitées pour des applications biomédicales. Dans la deuxième étude effectuée au cours de cette thèse (chapitre 2), nous avons préparé un nouveau type de SCNPs multifonctionnel à partir d’un polymère cristallin liquide. Il s’agit du polyméthacrylate de [2- (7-méthylcoumaryl) oxyéthyle - co - 6-[4-(4’-méthoxyphenylazo) phénoxy] hexyle] (PAzoMACMA). Les groupements latéraux du polymère contiennent, en majorité, des azobenzènes photoisomérisables et, en minorité, des coumarines photodimérisables. Les azobenzènes servent de mésogènes pour la formation de cristaux liquides alors que les coumarines ont été utilisées pour une réticulation photoinduite et intrachaîne. Malgré les dimensions inférieures à 15 nm, le confinement et la réticulation, les phases cristallines liquides (LC) persistèrent même dans les SCNPs. Ces SCNPs cristaux liquides (LC-SCNPs) présentèrent un certain nombre de propriétés intéressantes et particulières. Alors que leurs dispersions dans le THF n’étaient pas fluorescentes, celles dans le chloroforme l’étaient. En plus, ces nanoparticules s’aggloméraient quelque peu dans le chloroforme ce qui induisait des fluorescences différentes entre des SCNPs riches en isomères cis ou riches en isomères trans des azobenzènes. A cause de la photoisomérisation des azobenzènes, ces LC-SCNPs se déformaient sous irradiation comme le font les microparticules ou les colloïdes contenant des azobenzènes. Cependant, la déformation de ces nanoparticules dépend de la longueur d’onde de lumière polarisée. Alors que sous irradiation UV polarisée à 365 nm, l’élongation des SCNPs était perpendiculaire à la polarisation de la lumière incidente, sous irradiation visible polarisée entre 400 et 500 nm, l’étirement se faisait parallèlement à la polarisation. Finalement, un nanocomposite fut préparé par dispersion de LC-SCNPs dans une matrice de polyméthacrylate de méthyle (PMMA). Si celui-ci était étiré mécaniquement, les azobenzènes s’orientaient dans la direction de la déformation induite. Ces propriétés intéressantes des LC-SCNPs que cette étude a permis de dévoiler, suggèrent de nouvelles applications potentielles. Dans la troisième étude de cette thèse (chapitre 3), nous avons préparé une classe de SCNPs sensibles à la présence de CO2 et leurs agrégats micellaires auto-assemblés. D’un côté, des SCNPs ont été préparées à partir d’un polyméthacrylate de {(N, N-diméthylaminoéthyle)-co-4-méthyl-[7-(méthacryloyl)-oxyéthyl-oxy] coumaryle} (PDMAEMA-co-CMA). Lorsqu’elles sont dispersées en solution aqueuse, les nanoparticules individuelles peuvent subir des cycles réversibles d’expansion et de rétrécissement sous une stimulation alternative de CO2 et de N2 qui vont protoner et déprotoner les amines tertiaires. D’un autre côté, des SCNPs de type ‘Janus’ (SCJNPs) ont été préparées à partir d’un copolymère dibloc amphiphile : PS-b-P(DMAEMA-co-CMA) (PS correspond au polystyrène qui est hydrophobe). Ce type de SCJNPs peut s’autoassembler sous forme de micelles en solution aqueuse. Sous stimulation CO2 ou N2, l’expansion ou le rétrécissement à l’intérieur des particules permet de grands changements de volume. En plus, ces particules ont été étudiées comme potentiels nanoréacteurs pour des nanoparticules d’or (AuNPs) que ce soit sous formes SCNPs ou micelles SCJNPs. La vitesse de formation des AuNPs augmente sous bullage de CO2 et décroît sous N2. Cela permet de rendre possible cette réaction contrôlable par ces deux gaz. Qui plus est, utiliser des micelles de SCJNPs dont le volume peut être modifié sur un large intervalle en changeant l’intensité de la stimulation de CO2, permit d’obtenir des AuNPs de taille variable.
Abstract : With interests on nanoscience and nanotechnology for many applications, there is a demand for development of fabrication technology of ultra-small nano-size objects that allow for precise size control and tailored functionality. Recently, a new technology called ‘single-chain technology’, which manipulates a single polymer chain, becomes a rapidly-growing research topic. This technology provides a facile method to prepare polymer single-chain nanoparticles (SCNPs) with a typical size of 1.5-20 nm. Due to the ultra-small size-enabled unique properties, SCNPs have wide range of applications, including sensor, catalytic system, low viscosity coating, nanoreactor and biomedical applications. Through the contributions by many scientists in the past decade, the synthetic methodologies to fabricate SCNPs have been reported using various chemistries and been getting mature. However, there are still several unsolved problems in the field of SCNPs including functions and application. Stimuli-responsive polymers, as a class of smart materials whose properties can be changed by responding to external stimuli, have been widely used in energy and biomedical applications. Since their chemical and physical properties can be changed easily and efficiently via environmental control, stimuli-responsive polymers provide a potential pathway to preparing functional SCNPs. In this thesis, we are focusing on developing functional SCNPs, especially systems with multi-functions, and expanding their applications. To achieve this target, various stimuli-responsive polymers were prepared as polymer precursors and their stimuli-responsive properties were introduced into the SCNP systems by rational design of their chemical structures. The core of this thesis is comprised of three projects which deal with three classes of SCNPs from stimuli-responsive polymers. These stimuli-responsive SCNPs perform multi-functions and undergo certain change either in structure or morphology and properties. In addition, according to their variety of functions, each class of multi-functional SCNPs has diverse potential applications. In the first study presented in the thesis (Chapter 1), we prepared a class of sub-10 nm photodegradable and size-tunable SCNPs based on photo-responsive main-chain coumarin-based polyesters Poly{[7-(hydroxypropoxy)-4-(hydroxymethyl)coumarin adipate]-co- (polypropylene glycol adipate)} (CAPPG) through copolymerization of coumarin diol, adipic acid and polypropylene glycol (PPG). By incorporating coumarin moieties into the chain backbone of a polyester, dual photo-responsive reaction, i.e. photo-dimerization (>320 nm) and photo-induced chain scission (254 nm), occur under two different wavelengths of UV irradiation, enabling the preparation of sub-10 nm SCNPs and their photo-degradation property. The photo-degradability of SCNPs is evidenced under 254 nm UV irradiation for 3 h, which molecular weight of SCNPs decreasing from 13220 g/mol to 1385 g/mol. Moreover, the size of SCNPs can be tunable from 5.3 nm to 3 nm (hydrodynamic diameter) by varying the dimerization degree of coumarin moieties, that is simply controlled by the UV irradiation time. These results demonstrate a facile method to control the size of SCNPs without the need for synthesizing different polymer precursors. Finally, due to the biocompatible and biodegradable nature of polyester as polymer precursor, the SCNPs with photo-degradability and size-tunability have the potential to be exploited for biomedical applications. In the second study realized in this thesis (Chapter 2), we prepared a new type of multi-functional SCNPs from a side-chain liquid crystalline polymer (SCLCP), namely poly{6-[4-(4-methoxyphenylazo) phenoxy]hexylmethacrylate-co-4-methyl-[7-(methacr-yloyl) oxy-ethyl-oxy]coumarin} (PAzoMACMA). The polymer’s side groups comprise photo-isomerizable azobenzene in majority and photo-dimerizable coumarin in minority, with the former as mesogens and the latter for intra-chain photo-crosslinking. Despite the sub-15 nm size, confinement and crosslinking, the liquid crystalline (LC) phases of bulk PAzoMACMA persist in SCLCPs. Such LC-SCNPs exhibit a number of interesting and peculiar properties. While their dispersion in THF is non-fluorescent, when dispersed in chloroform, the nanoparticles appear to agglomerate to certain degree and display significant fluorescence that is different for SCNPs rich in the trans or cis isomer of azobenzene. The azobenzene LC-SCNPs also undergo photo-induced deformation, similar to azobenzene micro- or colloidal particles. However, the elongational deformation of the nanoparticles is dependent upon the linearly polarized excitation wavelength. While under polarized 365 nm UV irradiation the SCNP stretching direction is perpendicular to the light polarization, under polarized 400-500 nm visible light irradiation, the stretching takes place along the light polarization direction. Finally, an all-polymer nanocomposite was prepared by dispersing the LC-SCNPs in poly(methyl methacrylate) (PMMA), and mechanically stretching-induced orientation of azobenzene mesogens developed along the strain direction. The interesting properties of LC-SCNPs unveiled in this study suggest new possibilities for applications including bio-imaging and LC materials. As the third study in this thesis (Chapter 3), we studied a class of CO2-responsive SCNPs and their self-assembled micellar aggregates. On one hand, SCNPs are prepared from a random copolymer of poly{(N,N-dimethylaminoethyl methacrylate)-co-4-methyl-[7-(methacryloyl)oxyethyl-oxy]coumarin} (P(DMAEMA-co-CMA)). When dispersed in aqueous solution, individual nanoparticles can undergo reversible swelling/shrinking under alternating CO2/N2 stimulation as a result of the reversible protonation/deprotonation of tertiary amine groups. On the other hand, tadpole-like single-chain ‘Janus’ nanoparticles (SCJNPs) are prepared using an amphiphilic diblock copolymer of PS-b-P(DMAEMA-co-CMA) (PS is hydrophobic polystyrene). This type of SCJNPs can self-assemble into core-shell micellar aggregates in aqueous solution. Under CO2/N2 stimulation, the collective swelling/shrinking of SCJNPs within the micelle results in large, reversible volume change. In addition, both P(DMAEMA-co-CMA) SCNPs and PS-b-P(DMAEMA-co-CMA) SCJNP micelles are explored as gas-tunable nanoreactors for gold nanoparticles (AuNPs). The rate of AuNP formation increases under CO2 stimulation and decreases upon N2 bubbling, which makes it possible to tune the reaction rate up and down (on/off switching) by using the two gases. Moreover, using the micelles of SCJNPs, whose volume can be controlled over a wide range by adjusting the CO2 stimulation strength, variable-size AuNPs and their aggregates are obtained with continuous redshift of the surface plasmon resonance (SPR) into the long wavelength visible light region.

A series of eight novel bidentate ligands, designed for use in the construction of nickel-selective molecularly imprinted polymers (MIP's), have been prepared. The synthetic pathway was established by retrosynthetic analysis of the target molecules to the readily available precursors, pyridine-2-carbaldehyde (or 6-methylpyridine-2-carbaldehyde) and ethyl bromoacetate. The ligands were designed to contain an allyl group for co-polymerisation and amine and pyridyl nitrogen donors, located to permit the formation of 5-membered nickel chelates. The eight novel ligands and their respective precursors were characterized by elemental (high-resolution MS) and spectroscopic (IR and ¹H and ¹³C NMR) analysis. High resolution electron-impact mass spectrometry has also been used, together with B/E linked scan data, to explore the fragmentation patterns of selected ligands. The various nickel(ll) complexes were analyzed using spectroscopic techniques and, in some cases, elemental analysis; computer modelling has also been used to explore conformational effects and complex stability. Numerous MIP's, containing nickel(II) complexes of the bidentate ligands, have been prepared, using ethylene glycol dimethylacrylate (EGDMA) as the cross-linker, azobis(isobutyronitrile) (AlBN) as the polymerization initiator and MeOH as the porogenic solvent. The template nickel(II) ions were leached out with conc. HCI, and the nickel(II) selectivity [in the presence of Fe(Ill)] of the nickel-imprinted polymers was examined by ICP-MS analysis. The ICP-MS data indicate that the MIP's examined exhibit extremely high selectivity for nickel over iron.
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Age-related macular degeneration (AMD) is the largest cause of blindness for those over 65 in the developed world. There is currently no treatment for the retinal cellular loss associated with the disease. One potential therapy is to implant retinal stem cells into the eye using a biodegradable polymer scaffold. Blends of the biodegradable polymers, poly(L-lactic acid) (PLLA) and poly(D,L-lactic-co-glycolic acid) (PLGA) have been formulated into microspheres. The influence of changing processing parameters on the size and morphology of the microspheres has been studied. A human retinal pigment epithelial (APRE-19) cell line was shown to adhere, survive and proliferate on the surface of the microspheres in vitro. Assays have demonstrated that the nature of the blend influenced cell behaviour. Transplantation of retinal pigment epithelial (RPE) cells on a supportive matrix has also been investigated as a therapy for AMD. In view of AMD related pathology of the native RPE support, Bruch’s membrane (BM), transplanted RPE cells require a scaffold to reside on. Copolymers based on methyl methacrylate (MMA) and poly(ethylene glycol) methacrylate (PEGM) have been synthesised and chemically modified at the PEG terminus. These polymers were subsequently manufactured into a fibrous scaffold using an electrospinning technique and investigated as an artificial BM. RPE cells were shown to attach and proliferate successfully on the surface of the fibrous scaffold in vitro. Cell adhesion was significantly enhanced on scaffolds with the PEG chain terminus modification. Significantly less apoptotic cell death was also observed on these surfaces. The diffusion properties of these artificial membranes have also been investigated. In addition, the novel gelation of the produced copolymers under certain conditions has been studied

This thesis presents research toward the development of a simple inexpensive fracture toughness tool for polymeric materials. Experiments were conducted to test the specimen configuration and the fracture toughness tool against an established ASTM standard for polymer fracture toughness, D5045, and a commonly used four-point bend method. The materials used in this study were polycarbonate and high density polyethylene. Reductions in both the production time and the variability resulting from the preparation of the specimens were addressed through the use of specially designed fixtures. The effects from the razor cut depths used in the chevron notch were compared to the fracture toughness values obtained in order to determine the effect upon the validity of the fracture toughness.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005.
Includes bibliographical references.
Conducting polymers are a subset of materials within the electroactive polymer class that exhibit active mechanical deformations. These deformations induce stresses and strains that allow for conducting polymers to be used as an actuator for mechanical devices. Incorporation of conducting polymer actuators into mechanical devices requires electrochemical and mechanical characterization of varying polymer sample sizes and their active properties. Of particular interest, is the characterization of macro-length polymer samples, which have yet to be investigated. An understanding of conducting polymer films and their feasibility as an actuator in a mechanical device are required for the development of a conducting polymer based rotary motor. The conducting polymer, polypyrrole, was studied for its feasibility as an actuator for control surfaces on autonomous underwater vehicles. Enhancements to the actuator's performance were addressed following the feasibility study. The development of an electrochemical dynamic mechanical analyzer provides an instrument for characterization of the polymer's properties over a variety of sample sizes and actuation conditions. Finally, the application of polypyrrole as an actuator and possible enhancements combined with the characterization of macro-length polymers provides the necessary tools to develop a rotary motor. Enhancements to polypyrrole actuators in this study account for an increase in tip force of 350% and a seven fold increase in achievable strain.
(cont.) Completion of a novel electrochemical dynamic mechanical analyzer, construction of a finite rotary motor able to subtend angular displacements, and the developed embodiment of a polymer based rotary eccentric motor are accomplished in this study.
by Bryan D. Schmid.
S.M.

This thesis explores the use of polymer nanoreactors in catalysis as well as the use of water-soluble polymers in enzyme stabilisation. Chapter 1: An introduction to the literature currently covering the research topics relevant to the techniques used within this thesis, providing further background on the fundamental enzyme theory that is to be explored Chapter 2: This looks at the techniques available for tethering the catalyst triazabicyclodec-5-ene to the hydrophobic block of an amphiphilic block copolymer, synthesised by nitroxide mediated polymerisation and the assembly of these polymers. Chapter 3: The previously synthesised nanoreactors were used to catalyse Michael additions with varied loadings within the core of the micelles. Chapter 4: Looks into the effect of using water soluble polymers of varying molecule weights on the activity of Lipases Circular dichroism spectroscopy and stain tests were used as tools to indicate changes to the native structure and activity. Chapter 5: Thermostability of lipase was investigated, and the use of the water-soluble polymers to extend the lifetime of the enzyme in solution was investigated through monitoring changes in the melting temperatures as well as stability studies.

Polymers are among the most important of various oilfield chemicals and are used for a variety of applications in the oil and gas industry (OGI) including water and gas shutoff, drilling mud viscosity modification, filtration loss control (FLC), swellable packers, loss circulation material (LCM) pills, enhanced oil recovery (EOR), fracture treatment and cleanup, chemical placement, etc. The deposition and retention of polymer molecules in porous media and their interactions with rock and fluids present complex phenomena that can induce formation damage. Formation damage due to polymer retention can occur via mobility reduction in three possible mechanisms of polymer-induced formation damage: 1) pore-throat blocking, 2) wettability alteration (which can alter permeability), and 3) increase in reservoir fluid viscosity. Physical adsorption can also cause permanent permeability impairment (formation damage). This polymer-induced formation damage (causing a reduction in net oil recovery) continues to be a fundamental problem in the industry owing to the rather shallow understanding of the mechanics of polymer-brine-rock interactions and the polymer-aided formation damage mechanisms. Most models available for polymer risk assessments appear to be utilised for all scenarios with unsatisfying results. For example, only very little, if any, is known on how polymer type, particularly in the presence of brine type impact on formation damage. In order words, one of current industry challenges is finding effective polymers for high salinity environments. Also, the effect of polymer charge, as well as charges at the brine-rock interface are issues that require a deeper understanding in order to address the role polymer play in formation damage. Furthermore, no much recognition has been given to polymer rheological behaviour in complex porous media, etc. The OGI therefore still faces the challenge of the inability to correctly predict hydrolysed polyacrylamide (HPAM) viscosity under shear degradation; and consequently have not been able to meet the need of production predictions. The effect of the above mentioned factors, etc have not been fully integrated into the polymer formation damage modelling. In this PhD research work, theoretical, numerical, laboratory experiments and analytical methods were used to further investigate the mechanics of polymer-brine-rock interactions and establish the mechanisms for formation damage related to polymer application. Three different hydrolysed polyacrylamide (HPAM) products (SNF FP3630 S, 3330 S and FloComb C3525) were used in the experiments; while Xanthan gum was used in the simulation work. The following variables were considered: 1) polymer type, 2) effect of concentration, 3) effect of salinity/hardness, 4) effect of permeability and pore size distributions, 5) effect of inaccessible pore volume (IAPV) on retention, 6) effect of flow rate (where a special method was established to quantify the effect of flow rate on polymer retention). Laboratory rheological and adsorption experiments were designed and conducted. Experimental results indicate that higher concentration of calcium divalent ions in brine help promote polymer retention on rock surface. On the basis of the experimental results, empirical models were developed and validated to: 1) predict HPAM rheological behaviour over a wide range of shear rates, 2) predict salinity-dependent polymer-induced formation damage, 3) in addition, a modified screening model that can aid polymer selection for field application design is proposed. Overall, these models can therefore serve as useful tools, and be used for quick look-ahead prediction and evaluation of polymer related formation damage in oil and gas-bearing formations.

In this thesis, glucose responsive hydrogels based on cross-linked dextran molecules were studied to determine the diffusion rate of an insulin analogue. Investigations of the interaction between concanavalin A and dextran, both in free solution and in the form of glucose responsive hydrogels were conducted. The free solution results have shown that there is an increase of association constant between concanavalin A and dextran when the molecular mass of the dextran is increased. Free solution viscometric tests have shown that increasing the molecular mass or the concentration of the dextran increases the viscosity. The hydrogels have been shown to form for dextrans of molecular mass 43kD or greater. Experiments conducted with hydrogel membranes in a diffusion cell have shown that the batch to batch reproducibility of hydrogel transport properties is low. However, clear evidence of glucose enhanced transport was obtained and these results were compared with predictions obtained from a theoretical model of gel permeability that accounts for competitive displacement of affinity cross links. Oscillatory rheological tests of gelation mixtures which showed an increase in complex viscosity at the gel point with increasing molecular mass of dextran were in agreement with empirical observations that gels formed from the highest molecular mass dextrans were more physically robust and easier to handle. Swelling rate experiments have shown that the rate of hydration of a hydrogel in the presence of glucose is decreased due to the osmotic pressure of the glucose. This work has shown that the multivalent nature of concanavalin A may not be a necessary pre-requisite for this type of hydrogel due to spatial constraints decreasing the number of potential affinity bonds per tetramer. In-house production of more tightly defined dextrans might be expected to reduce heterogeneity and improve the reproducibility of this type of hydrogel membrane.

This thesis is concerned with the continued development of multisensor array sensing technology for the detection and classification of aromas. The technology applies the use of conducting polymers grown across a gap between metallic conductors. The electrochemically deposited films complete a circuit and providing electrical resistance. In this format the films act as chemical resistors (chemiresistors) the current flow being influenced by the polymers' molecular electronics. Devices of this nature are potentially useful as sensors for analytes which cause the reversible modulation of the films' molecular electronics, leading to a detectable resistance change. Variation in the chemical and physical properties of the conducting polymer films has led to the generation of sensing devices capable of providing rapid, meaningful sensory information. The development of multisensor arrays containing a series of sensing devices having broad ranging sensitivities, has enabled effective discrimination of sample analytes. The information generated from such an array provides a 'fingerprint' or patterned response relating directly to the sample analyte. Complex statistical processing techniques have been coupled with the sensor technology to categorise and differentiate between the 'fingerprints' obtained. Instrumentation based on multisensor array technology has been developed by Neotronics Scientific Ltd., who currently market the NOSE (Neotronics Olfactory Sensing Equipment) based upon conducting polymer sensors. The research project resulting in this thesis was intended to develop and examine conducting polymer chemiresistor technology and explore the parameters that contribute to the production of effective discriminating sensors for use in array devices. The study involved an investigation of the variables involved in the electropolymerisation protocols, and expansion of the sensing chemiresistors available. This was achieved by analysis of polymer fabrication methods, and the variation in monomer and electrolyte feedstocks used during polymerisation. Polymer film stability was a major feature of the work performed as the long-term effectiveness of a sensing device is governed by environmental stability allowing reproducible analysis. Sensor optimisation was investigated using an individual system to determine the effect of the electrodeposition protocols, surface morphology, baseline resistance and film thickness. Polymer composition and stability were studied using a series of electrochemical, spectroscopic and surface analysis techniques. The data obtained resulted in the fabrication of chemiresistors not previously tested in electronic nose technology. Experimental optimisation studies also allowed variation in the nature of the responses obtained. A final area of investigation was the analysis of chemiresistors within a multisensor array environment using the NOSE technology. A series of arrays were prepared and the sensors exposed to a number of single, pure, organic analytes. From this data information was obtained on sensor response relating to molecular size, shape, position and nature of functional groups. The multifaceted nature of these experiments increased the number and response characteristics accessible to Neotronics, and provided a contribution to the knowledge surrounding the interactions between conducting polymer films and volatile organic analytes.

Cette thèse propose une approche rationnelle pour le design de polymères à empreintes moléculaires (MIPs) pour la détection de nitro-explosifs. Les polymères à empreintes moléculaires qui miment la reconnaissance moléculaire biologique, ont l’avantage d’être stables dans des environnements sévères et peuvent adopter différentes formes physiques pour le couplage avec des transducteurs. Leur synthèse est basée sur la co-polymérisation de monomères fonctionnels et réticulants en présence de la molécule cible, ou comme dans cette thèse, d’un analogue ayant une structure proche de celle de la molécule cible. Cela conduit à la formation d’un réseau polymérique tridimensionnel rigide avec des sites de liaison complémentaires en taille, forme et position des groupes fonctionnels de la molécule cible ou de l’analogue. Pour identifier le meilleur monomère fonctionnel pour notre molécule cible, une approche rationnelle basée sur la modélisation moléculaire, la résonance magnétique nucléaire (RMN) et le titrage par calorimétrie isotherme (ITC) a été utilisée. Elle permet d’optimiser le mélange de pré-polymérisation pour identifier le monomère fonctionnel interagissant le plus fortement avec la molécule cible. Les résultats obtenus ont été confrontés à des études de liaison à partir de polymères synthétisés. La formulation polymérique ainsi conçue est intégrée aux surfaces du transducteur sous forme de nanoparticules, de films et de nanoparticules incorporés dans des films de polydopamine électropolymérisés. En plus des polymères traditionnels obtenus par polymérisation radicalaire classique sous forme de particules, des films de MIP à base de polydopamine électropolymérisés ont été étudiés en tant qu'approche alternative pour la détection électrochimique de nitro-explosifs
This thesis proposes a rational design approach towards molecularly imprinted polymers (MIPs) for sensing nitro-explosives. Molecularly imprinted polymers are mimicking biological molecular recognition. They have the advantage to be stable in harsh environments and can be tailored into different physical forms for interfacing with transducers. Their synthesis is based on the co-polymerization of functional and cross-linking monomers in the presence of the target analyte or, as in this thesis, with a structural analogue leading to a rigid three-dimensional polymer network with binding sites complementary to the template in size, shape and position of the functional groups. The choice of the functional monomer was carried out with a rational design approach combining molecular modelling, nuclear magnetic resonance (NMR) and isothermal calorimetry (ITC) studies. This allows to optimize the pre-polymerization mixture in order to get strong complexation between the functional monomer and the template. The obtained results were confronted with binding studies performed on synthesized polymers. The thus designed polymer formulation was interfaced with transducer surfaces in form of nanoparticles, films and nanoparticles embedded into electro-polymerized polydopamine films. In addition to the traditional MIPs by free radical polymerization, molecularly imprinted in-situ electro-polymerized polydopamine films were investigated as an alternative approach for sensing nitro-explosives electrochemically

One of the biggest challenges for the semiconductor industry is the development of nanofabrication techniques that allow for the fabrication of structures on a scale tens of nanometers in size. This provides greater potential functionality at reduced costs. Established conventional techniques, such as photolithography, are unable to achieve features below 30 nm due to the inherent limitations of the wavelength of light sources currently available. For this reason block copolymers received considerable attention in order to overcome these challenges in lithographic technology. Block copolymers have an inherent processing advantage of self assembling into various nanoscopic structures such as spheres, cylinders and lamellae amongst others on a scale below 50 nm. The dimensions and structures are readily tuneable based on molecular weights (Mw) and compositions of the copolymers. However, to be usable within industry a great deal more research still needs to be conducted on the use and nature of block copolymers. In this study the block copolymer of poly(styrene-block-methylmethacrylate) (PS-b-PMMA) was investigated as a potential nano-mask for semiconductor growth. Research was conducted on thin films of PS-b-PMMA by altering the parameters influencing the kinetics and thermodynamic effects on the thin films, in order to produce a structure of cylinders of PMMA perpendicular to the substrate within a PS matrix on a silicon (Si) substrate. It is shown that thermally annealing the PS-b-PMMA thin films under conditions where there is no preferential interaction of the substrate or open surface with either components of the block copolymer (i.e. PS or PMMA with Si or ambient) and at an appropriate thin film thickness, perpendicular cylinders of PMMA within a PS matrix form in the thin films. The determined ideal thin film thickness is 32 nm, with non-preferential interaction attained between block and substrate by coating a poly(styrene-random-methylmethacrylate) (PS-r-PMMA) on the Si substrate and annealing within a vacuum. Additionally, acetic acid, as a known selective solvent of PMMA, is used to further process the thin film of PS-b-PMMA. Thus a final PS nano-mask containing pores with a diameter tens of nanometers in size is produced. The pores are shown to have an average diameter of 13.5 nm. Measurements were taken throughout the investigation using a scanning probe microscope (SPM) to determine surface topography and phase morphology of the PS-b-PMMA thin films. X-ray reflectometry (XRR) is used to measure film thickness. The research in this study shows that thin films of PS containing hexagonally arranged pores can be produced and could find potential use as a nano-mask for semiconductor growth.

Thesis (Ph. D.)--University of Oregon, 2007.
Typescript. Includes vita and abstract. Includes bibliographical references (leaves 94-100). Also available for download via the World Wide Web; free to University of Oregon users.

Dissertação para obtenção do Grau de Doutor em Química Sustentável
Within the last decade, the interest in molecularly imprinted polymers (MIPs) has strongly increased because of their promising applications in separation processes, drug delivery, biomimetic sensing and catalysis. This thesis reports the development of MIPs using supercritical fluid technology as a viable and greener alternative to the synthesis and processing of these molecular recognition polymers. The affinity to the target molecule was introduced by means of non-covalent and semicovalent molecular imprinting and the performance of the materials was evaluated in specific applications of drug delivery, chiral chromatography and adsorption of environmental pollutants. The influence of experimental parameters, such as crosslinking degree, functional monomer nature and template: monomer ratio, on molecular recognition was investigated. The results show that it is possible to tune the affinity of the polymers by optimizing the imprinting reactional mixture. MIPs show higher loading capacities and affinity constants to the template molecule, both in supercritical and aqueous environments. Hybrid membranes were prepared by a scCO2-assisted phase inversion method, showing that imprinted particles can be immobilized into porous structures introducing affinity to the materials. Further, HPLC experiments attested that the synthesized MIPs have high selectivity towards the template, as an enantiomeric differentiation was achieved when the racemic mixture was loaded into the imprinted polymeric stationary phase. The work developed in this thesis contributes to the consolidation of scCO2 as alternative solvent and demonstrates the feasibility of synthesizing clean, easy-to-make and ready-to-use molecular recognition polymers using sustainable technologies.
Fundação Ciência e Tecnologia - grant SFRH/BD/31085/2006 and projects PTDC/QUI/66086/2006 and PTDC/QUI-QUI/102460/2008

Thesis (Ph. D.)--Biomedical Engineering, Georgia Institute of Technology, 2008.
Committee Chair: Nie, Shuming; Committee Member: Bao, Gang; Committee Member: Chung, Leland; Committee Member: Murthy, Niren; Committee Member: Prausnitz, Mark.

This research had the specific goal of synthesizing a monomer for the development of polymers with unique physical properties. The expected physical property to be pursued is that of an innate elasticity within the monomer itself. As such, bis-1,10-((6-azidohexyl)oxy)bicyclo[8.8.8]hexacosane (target 1) was synthesized with the expectation that the bicyclic core would have the freedom of movement necessary to provide such elasticity. The addition of the azide functional groups to the target molecule may be used in the well known Huisgen 1,3-cycloaddition reaction to form a polytriazole polymer when matched with another monomer containing the requisite terminal alkyne. For this purpose, and further study of the elasticity of the bicyclo[8.8.8]hexacosane core, bis-1,4-((5-hexynyl)oxy)benzene (target 4) was synthesized for the formation of the polytriazole, and bis-1,4-((6-azidohexyl)oxy)benzene (target 5) was synthesized to form a polytriazole analog without the elastic bicycle in the polymeric repeating units.

Mucoadhesive dosage forms are delivery systems able to adhere to a particular region of the body for extended periods of time. This can lead to several advantages, such as a reduction of the administration frequency and an enhancement of drug bioavailability. For this reason, the phenomenon of mucoadhesion is widely studied, despite not fully understood. The mucoadhesive properties come from polymers, especially hydrophilic polymers becoming adhesive once activated by moistening. The mucoadhesive polymers play the key role in determining the mucoadhesive ability of a dosage form. Hence, it is necessary to deepen the study of the polymers properties. The present research mainly focuses on the screening of different mucoadhesive polymers for the development of mucoadhesive tablets with intestinal target. Particularly, this research aims to study different factors affecting mucoadhesion in order to identify the most important one that might predict the mucoadhesive ability of the final solid dosage form. Results of research activities are summarized in five chapters: - Chapter 1 gives an overview on the phenomenon of mucoadhesion, and the methods for the detection of the mucoadhesive properties; - in Chapter 2 the methods developed for the study of tablets mucoadhesive properties are presented; - the influence of the amount of polymer on the mucoadhesive properties and on the release rate of a model drug (sodium butyrate) is analyzed in Chapter 3; - in Chapter 4 the Design of Experiment (DoE) techniques are used to develop tablets with good mucoadhesive properties and an extended-release, containing sodium butyrate or mesalazine as active ingredients; - Conclusions and proposals for the future work can be found in Chapter 5.
Le formulazioni mucoadesive sono sistemi in grado di aderire ad una particolare regione del corpo per un tempo prolungato. Numerosi sono i vantaggi che ne derivano, tra cui la riduzione della frequenza di somministrazione del farmaco ed anche un possibile aumento della biodisponibilità. Per questo motivo, il fenomeno di mucoadesione è ampiamente studiato in campo scientifico. Nonostante ciò, a causa della sua complessità non è stato ancora compreso del tutto. Le proprietà mucoadesive di una formulazione derivano dalla presenza di polimeri, generalmente idrofilici, in grado di aderire alle mucose in seguito ad idratazione. I polimeri mucoadesivi, quindi, ricoprono un ruolo chiave nel determinare le capacità mucoadesive di una formulazione e risulta fondamentale studiare in maniera approfondita le proprietà del polimero. Il focus della presente ricerca è lo screening di diversi polimeri, al fine di sviluppare compresse mucoadesive che abbiano come target la mucosa intestinale. In particolare, sono stati studiati diversi fattori in grado di influenzare le proprietà mucoadesive di una formulazione allo scopo di individuare la proprietà più importante che potrebbe fornire un’informazione di tipo predittivo sulla capacità mucoadesiva del prodotto finito. I risultati di questo studio sono riassunti in cinque capitoli: - il Capitolo 1 fornisce una panoramica sul processo di mucoadesione e sui metodi per valutare le proprietà mucoadesive; - il Capitolo 2 presenta i metodi, che sono stati sviluppati in questo lavoro di ricerca, per lo studio delle proprietà mucoadesive delle compresse; - nel Capitolo 3 viene analizzata l'influenza della quantità di polimero sulle proprietà mucoadesive e sulla velocità di rilascio di un farmaco modello (sodio butirrato); - nel Capitolo 4 vengono impiegate tecniche di Disegno Sperimentale al fine di sviluppare compresse mucoadesive a rilascio prolungato contenenti sodio butirrato o mesalazina come principi attivi; - Conclusioni e prospettive future sono esposte nel Capitolo 5.

Alkali activation has been emerging as a sustainable technology to produce innovative construction materials. Alkali-activated materials have been extensively investigated, but different levels of scientific understanding and industrial implementation can be found among several subgroups of such materials. The most widely examined alkali-activated materials are commonly known as geopolymers. The scientific knowledge of their reaction mechanisms and structures is mature, and their market implementation fairly consolidated. Conversely, inorganic polymers (IP) is a different subgroup of alkali-activated materials since their chemistry does not exactly correspond to the definition of geopolymers. These systems are challenging but unlikely geopolymers can admit a wide range of precursors offering an opportunity to valorize low-value raw materials that include several wastes and industrial by-products. The diversity of precursors that can be used in IP production hinders the definition of production guideposts, and dedicated research is needed to define ad hoc mix designs according to the precursors’ characteristics and envisioned applications. This doctoral research was focused on the multiscale development of inorganic polymers and the conceptual design of sustainable and multifunctional materials for near-zero energy consume buildings. Vitrified residues produced during the thermochemical conversion of refused derived fuel were taken as a representative case study of a broad group of currently underutilized industrial by-products, namely calcium-iron-rich slags. The aim of this work was to understand the fundamental processing parameters affecting the reaction mechanism involved in the formation of calcium-iron-rich IPs and their correlation with the chemical and physico-mechanical properties of the developed materials. The major technological constraints related to the use of such slags as IP precursors were examined, and the most suitable production conditions to obtain IP products with enhanced properties identified. A broad range of IP materials with engineered properties was developed and optimized. The efforts made in developing predictive models, in optimizing mixture proportions and in minimizing the shrinkage of IP binders and mortars are described. Optimized products characterized by a high dosage of residues in their composition, increased volumetric stability, excellent mechanical properties, and good residual characteristics after exposure to high temperatures were developed. The functionalization of IP mortars was addressed, and the effects of incorporating phase change materials in the mix design investigated. Lightweight IPs were developed using different processing routes, and their mechanical and thermal properties examined. Different IP products were used to develop multi-layer sandwich panels that were both thermal insulating and reactive to temperature fluctuations. The problematics related to their upscaling were analyzed, and the production processes optimized. Semi-industrial sandwich panels were produced to demonstrate the feasibility of the solutions proposed. The topic analyzed in this doctoral research and the insights provided are a significant contribution to the implementation of alkali-activation technology as a viable upcycling solution for industrial by-products, and particularly interesting to the construction sector in which current efforts to achieve lower environmental impacts are considerable. The use of calcium-iron-rich slags, like the ones produced in thermochemical conversion processes, in such production schemes is a plausible large-scale upcycling route that can absorb significant volumes of those residues and, by doing so, contribute to increasing the sustainability of industrial sectors in which such residues are produced.
I leganti ad attivazione alcalina (nella formulazione originale inglese “alkali-activated materials”) stanno sempre più affermandosi come soluzione tecnologica sostenibile ed innovativa nella produzione di materiali da costruzione. Molti lavori esistono al riguardo, ma il livello di comprensione scientifica e di implementazione industriale di questi materiali, varia a seconda dei diversi tipi di leganti ad attivazione alcalina a cui si fa riferimento. I materiali ad attivazione alcalina più studiati sono i geopolimeri. I meccanismi e le reazioni coinvolte nella formazione di questi materiali sono ormai noti e consolidati da tempo nella comunità scientifica, così come la loro implementazione sul mercato. Un diverso sottogruppo dei materiali ad attivazione alcalina sono i polimeri inorganici (“inorganic polymers”). La loro chimica differisce dai geopolimeri in quanto non ottenuti dall’esclusiva attivazione alcalina di materiali allumino-silicatici. Gli polimeri inorganici derivano da sistemi chimicamente complessi ma sono allo stesso tempo versatili. Contrariamente ai geopolimeri infatti, i polimeri inorganici possono essere prodotti utilizzando una vasta gamma di precursori, offrendo quindi l’opportunità di valorizzare materie prime di basso costo che includono anche numerosi rifiuti e sottoprodotti industriali. Tuttavia, l’ampia varietà di questi materiali fa sì che studi ad hoc siano necessari per ogni potenziale precursore in funzione della sua composizione chimica e dell’applicazione finale prevista. La presente tesi di dottorato è finalizzata allo sviluppo di materiali da costruzione funzionalizzati e sostenibili, utili alla realizzazione di edifici ad un consumo di energia quasi zero (“near Zero Energy Building, nZEB”) e messi a punto attraverso lo studio di polimeri inorganici prodotti da rifiuti non altrimenti valorizzabili: le scorie vetrose ottenute dalla conversione termochimica di combustibili derivato da rifiuti (CDR). Caratterizzati da alti contenuti di Ca e Fe, questi residui possono essere considerati rappresentativi di un più ampio gruppo di rifiuti e sottoprodotti attualmente scarsamente utilizzabili e spesso destinati al conferimento in discarica. Obiettivo principale del presente lavoro era quello di comprendere i meccanismi delle reazione coinvolte nella formazione di polimeri inorganici ottenuti dall’attivazione alcalina di queste scorie, e di determinarne le correlazioni con le proprietà chimiche e fisico-meccaniche del prodotto finale. Attraverso l’uso di modelli statistici predittivi, sono stati sviluppati, ottimizzati ed ingegnerizzati un’ampia gamma di polimeri inorganici. I risultati sperimentali riportati nel presente lavoro riguardano innanzitutto lo sviluppo e l’ottimizzazione di mix design, in grado di massimizzare il contenuto di scoria come precursore. Altro aspetto molto importante di studio ha riguardato la riduzione dei ritiri per una migliore stabilità volumetrica di leganti e malte prodotti a partire dagli polimeri inorganici ottimizzati. Eccellenti proprietà meccaniche e buone prestazioni residue dopo l’esposizione alle alte temperature, sono fra le principali proprietà analizzate che caratterizzano le formulazioni sviluppate. Con lo scopo di ottenere un prodotto in grado di incrementare l’efficienza energetica degli edifici, un importante parte del lavoro ha riguardato la funzionalizzate del materiale sviluppato. L’ingegnerizzazione della microstruttura, per ottenere un materiale leggero e termicamente isolante, e l’aggiunta di materiali a cambiamento di fase (“Phase Change Materials, PCMs”), capaci di ridurre le fluttuazioni termiche, sono le due principali tematiche tecnologiche investigate. Tale studio ha portato alla realizzazione di panelli multistrato in grado di offrire entrambe le proprietà termiche desiderate. Attraverso l’ottimizzazione dei parametri di produzione, compatibili con i requisiti di scalaggio industriale, sono stati realizzati in laboratorio prototipi in scala naturale, che dimostrando la piena fattibilità tecnica delle soluzioni proposte. Il tema proposto e gli approfondimenti forniti in questa tesi di dottorato sono di particolare interesse per il settore delle costruzioni, sempre più attento a soluzioni innovative capaci di ridurre l’impatto sull’ambiente. La valorizzazione di scorie ricche in calcio e ferro, così come proposta nel presente lavoro, rappresenta una plausibile via di riciclo su larga scala in grado di assorbire significativi volumi di scarti. Valorizzare questi rifiuti convertendoli in materiali da costruzione che, nella loro vita utile, consentono di ridurre l’impatto energetico degli edifici, ha quindi un elevato beneficio che è sia economico che ambientale.

In recent decades, scientific research giving more attention to the development of bio-based polymer composites due to the extensive usage of petroleum based fillers as well as polymer matrices for the generation of polymer composites. It is a well-known fact that the petroleum derived polymer composites raise inevitable issues such as environmental pollution, waste management and depletion of petroleum resources etc. So it is important to develop fully or partially biodegradable polymer composites without compromising the mechanical, physical and thermal properties which are required for the end use applications. In this investigation, two different types of filler materials such as sisal fibres and halloysite nanotubes were used to prepare PLA polymer composites and their morphology, physical, mechanical, dynamic mechanical, thermal, water absorption and biodegradable properties were studied. This work also involves the preparation and properties of polypropylene composites reinforced with sisal fibres and halloysite nanotubes to compare the mechanical and thermal properties with PLA composites. First, surface treatment was performed for sisal fibres in order to remove the amorphous materials such as hemicellulose, lignin and pectin from the surface of the fibres which enhances the fibre-matrix interfacial strength and mechanical properties of the fibres and their polymer composites. Sisal fibres were subjected to different surface treatments such as alkali, high intensity ultrasound (HIU), and the combination of alkali and HIU and their effects on the morphology, fibre diameter, moisture absorption, mechanical and thermal properties of untreated and surface treated sisal fibres were studied. Fourier transform infrared spectroscopy (FTIR) and field emission scanning electron microscopy (FE-SEM) results confirmed the removal of amorphous materials after the combined treatments of alkali and ultrasound. Moisture absorption and diameter of the sisal fibres were significantly reduced by 40 and 200% respectively after the combination of alkali and HIU treatment as compared to untreated sisal fibres. TGA results revealed that the thermal stability of sisal fibres obtained with the combination of alkali and HIU treatment significantly increased by 38.5 oC as compared to the untreated fibres. Tensile properties of single fibre showed a reduction in the tensile strength and modulus by 25% and 26% respectively as compared to the untreated sisal fibre owing to surface treatments. A reduction in the tensile properties is mainly due to the removal of amorphous materials from the surface of sisal fibres which act as binding materials for cellulose. Second, the effect of different surface treatments on the morphology, mechanical, thermal, water absorption and biodegradable properties of sisal fibres reinforced PLA (SF/PLA) composites has been investigated. For this, different ratio of untreated and surface treated sisal fibres was mixed with PLA polymer matrix by using an internal mixer. Compounded materials from the internal mixer were subjected to compression moulding to prepare the test specimens. FE-SEM analysis confirmed the good dispersion of different surface treated SF in the PLA composites. The tensile strength and modulus increased by 10 and 75.4% for 15 wt% and 30 wt% of fibre loading respectively with the combined treatment of alkali and HIU PLA composites as compared to the untreated fibre reinforced PLA composites. Young’s modulus of the composites has also been predicted by using the theoretical models which fit well to the obtained experimental values. Dynamic-mechanical analysis (DMA) revealed that the combination of alkali and HIU treated SF/PLA composites showed an increase in the storage modulus by 15% and 30% as compared to the untreated fibre composites and pure PLA respectively. TGA and DSC analysis revealed that the thermal stability and crystallinity increased significantly for the PLA composites reinforced with sisal fibres of combined treatment of alkali and HIU. Water absorption study showed a considerable reduction in the water absorption and coefficient of diffusion by 136% and 130% respectively for the combination of alkali and HIU treated SF/PLA composites as compared to untreated SF/PLA composites. The degradation of SF/PLA composites was studied by composting the samples into the soil. A significant weight loss of 17.87% could be observed for the addition of 30 wt% of untreated SF/PLA composites after soil composting for 120 days. Apart from sisal fibres, halloysite (Hal) nanotubes were also used as reinforcement fillers to study their effectiveness in improving the mechanical and thermal properties of PLA nanocomposites. Hal nanotubes were surface modified with 3-aminopropyltriethoxysilane (APTES) to enhance the surface interaction of Hal nanotubes with PLA and to achieve good dispersion of Hal nanotubes across the PLA matrix. Nitrogen adsorption-desorption, FTIR and TGA analysis results were confirmed the successful modification of Hal nanotubes surface with APTES. The different wt% of unmodified and APTES modified Hal-PLA nanocomposites were prepared by using internal mixer and compression moulding machine. The resultant Hal-PLA nanocomposites were characterized for their morphology, thermal, mechanical and dynamic-mechanical properties. Tensile strength increased to 62.6 MPa with the addition of 4 wt% of APTES modified Hal-PLA nanocomposites which is 26.5% higher than pure PLA and 15% higher than unmodified (4 wt%) Hal-PLA nanocomposites. Impact strength of 4 wt% APTES modified Hal-PLA nanocomposites increased by 20% and 40% as compared to unmodified Hal-PLA nanocomposites and the pure PLA respectively. TGA analysis revealed that the thermal stability increased significantly by 17 oC with the addition of 4 wt % of APTES modified Hal nanotubes onto PLA. Storage modulus increased by more than 10% with the addition of 4 wt% of APTES modified Hal nanotubes as compared to pure PLA. To compare the PLA composites with conventional polymer matrix composites, composites of polypropylene (PP) were prepared by reinforcing with sisal fibres and Hal nanotubes and the effect of surface treatment of sisal fibres and surface modification of Hal nanotubes on the mechanical and thermal properties of SF/PP and Hal-PP nanocomposites were studied. Tensile properties were increased for the combined treated SF/PP composites as compared to the untreated and pure PP. Tensile modulus and strength increased by more than 50% and 10% respectively as compared to the untreated SF/PP composites. TGA and DSC results revealed that the combination of alkali and HIU treatments increased the thermal stability and crystallinity by 8 oC and 8% respectively as compared to untreated SF/PP composites. DMA analysis confirmed the significant enhancement of storage modulus for the combined treated SF/PP composites by 50% as compared to pure PP. Mechanical and thermal properties were studied for unmodified and APTES modified Hal nanotubes reinforced PP nanocomposites. The investigations suggest that the mechanical properties of APTES modified Hal-PP nanocomposites were found to be superior to the unmodified Hal-PP nanocomposites. The tensile strength and modulus increased by 31 and 72% with the addition of 6 wt% of APTES modified Hal-PP nanocomposites as compared to pure PP. Impact strength also increased by 44% than pure PP with 6 wt% loading of APTES modified Hal nanotubes. Thermal analysis revealed that the thermal stability and percentage crystallinity increased by 15 oC and 22% respectively for the Hal-PP nanocomposites with surface modification by APTES. DMA analysis shows the improved storage modulus by 28% as compared to pure PP. Based on the present work, it can be said that the sisal fibres and Hal nanotubes have potential as reinforcing materials in the generation of fully bio-based polymer composites.
However, surface treatments and/or modification were playing an important role in order to tune the required mechanical and thermal properties of the polymer composites. This study also proved that in comparison to the conventional polymer matrix materials such as PP, PLA is a strong competitor with respect to its good mechanical properties and improved thermal stability apart from the fact that PLA is one of the best known biodegradable and biocompatible polymer matrices in the current market to use not only in medical application, but also in various commercial applications such as packaging, automotive and home appliances.