Chitin crystallites were prepared from crab chitin using HCl hydrolysis. On avenge, the surface charge density of the chitin crystallites was calculated to be 0.5 e/nm2 based on conductimetric titration data. The formation of a chiral nematic phase in aqueous suspensions of chitin crystallites and the in situ texture of the crystallite suspensions were investigated using polarised optical microscopy and freeze-fracture transmission electron microscopy. The effect of the interparticle electrostatic interaction on phase separation has been explored through phase diagrams and the interaction energy was calculated based on experimental zeta potentials. The flow properties of the liquid crystalline phases of chitin crystallites have been studied rheologically. Shear thinning behaviour and a two-regime flow curve were observed for isotropic suspensions and biphasic suspensions respectively. A typical three-regime flow curve for liquid crystalline polymers was found for the anisotropic suspension of chitin crystallites. The maximum in the viscosity-concentration curve was found at the phase transition concentration: isotropic to biphasic. Chitin crystallites were systematically deacetylated using NaOH hydrolysis. It was found dud the reaction was pseudo first order. These modified crystallites are highly charged. Their phase behaviour contradicts the theoretical prediction by Stroobants et al. in addition, crystallites with a different extent of N-sulfonation were obtained in an aqueous medium using triethylamine/sulfur trioxide (TEA/SO3) by controlling the TEA/SO3 concentration used in the reaction. The colloidal behaviour of the suspension of the N-sulfonated crystallites was studied by plotting the zeta potential of the suspension as a function of the pH. Once the extent of N-sulfonation reached a certain level (80% or above), the chiral nematic; phase formed while below this level only the nematic phase was observed. TEM studies showed that the crystallites were wel

Fluorinated organic-inorganic hybrid polymers have attracted interest over the last decade for their potential in guided wave optics. Some examples include tunable optical filters, switches, splitters, directional couplers, and modulators. Our study focuses on the synthesis and polymerization of a series of alkoxysilane monomers derivatized with different fluorinated functionalities. These monomers were prepared with a view to have a well defined refractive index, optical transparency, optical loss, mechanical flexibility, thermal stability and ease of processing. Hydrolysis and condensation experiments are performed on these monomers with different H2O:Si molar ratios to monitor the formation of siloxane backbones from fluoroaryl functionalized alkoxysilanes through the sol-gel process. These results are examined by NMR spectroscopy. A non-hydrolytic route to organically modified low-OH Ti/Si hybrid polymers is also studied. These polymers are synthesized by the use of boric acid for hydrolysis and titanium ethoxide, along with fluoroaryl functionalized alkoxysilane precursors for condensation. Homogenous films are made from the sol phase fluids and photolithographic experiments are conducted to fabricate waveguides. / Durant la dernière décennie, les matériaux polymères hybrides organique-inorganiques fluorés ont attiré une attention considérable en raison de leurs potentiels comme guides d’ondes optiques. Certains exemples ont demontré leurs efficacités en tant que filtres optiques accordables, commutateurs, doubleurs, coupleurs directionnels, et modulateurs. Notre étude s’est concentrée sur la synthèse et la polymérisation d’une série de monomères d’alkoxysilane fonctionnalisés par différents groupements fluorés. Ces monomères ont été préparés en vue d’obtenir des caractères bien définis tel que l’indice de réfraction, la transparence optique, la perte optique, la flexibilité mécanique, la stabilité thermique et la simplicité de préparation. L’hydrolyse et la condensation de ces monomères ont été menées en présence de différents ratios molaires de H2O:Si afin de suivre la formation des enchaînements siloxanes à partir d’alkoxysilanes fonctionnalisés par des groupements aromatiques fluorés via le procédé sol-gel. Ces résultats ont été examinés par spectroscopie RMN. Une voie non-hydrolytique pour la synthèse de matériaux polymères Ti/Si hybrides, modifiés organiquement et à fonctionalité–OH réduite, a été également étudiée. Ces polymères ont été synthétisés grâce à l’hydolyse en présence d'acide borique et condensation en présence d’éthoxide de titane, avec des précurseurs d’alkoxysilane fonctionnalisés par des groupements aromatiques fluorés. Des films homogènes ont été préparés de ces fluides sol phase et des études photolithographiques ont été conduites pour la fabrication de guides d’ondes.

The morphology of diblock ionomers consisting of non ionic polystyrene blocks and ionic poly(cesium methacrylate), or poly(cesium acrylate), or poly(4-vinylpyridinium methyl iodides) blocks in solution and in the solid state is investigated by small angle x-ray scattering (SAXS). / When the polystyrene blocks are kept short, they self-assemble in bulk to form spherical microdomains. Furthermore, the polystyrene segments are highly stretched in the non ionic microdomains, as was also observed previously for the ionic segments of comparable lengths in the ionic microdomains. These findings support the hypothesis that chain extension in microdomains of diblock ionomers in bulk is the result of the high surface energy and not of the ionic character of one of the blocks. The presence of spherical ionic domains in diblock ionomers with short ionic blocks is confirmed by electron micrographs. An increasing size of the ionic microdomains for diblocks with a high polydispersity in the ionic chains relative to that in samples of low polydispersity is seen only in samples prepared close to thermodynamic equilibrium, such as casting from a solvent which is good for both blocks. / When diblock ionomers of short ionic block lengths are dissolved in a solvent selectively good for the polystyrene block, micelles are formed which consist of ionic cores surrounded by a corona of polystyrene segments swollen by the solvent. The core size depends only on the ionic block length, and varies as the 3/5 power of the number of units in the ionic block, as predicted by the star model for block copolymer solutions. The ionic cores have a low polydispersity in sizes. The sizes are independent of the chemical structure, of polymer concentration, of polystyrene block length, and of solvent composition provided it is of low polarity. Water can be solubilized into the ionic cores up to a limit. Aggregation number, surface area per chain and micellar mass can be obtained from the SAXS results. The micelles show a high degree of organization in solution, as evidenced by the presence of a structure peak even at 1% polymer concentration; up to three peaks are seen for solutions above 2% polymer concentration. The possible scattering models that could explain the observed structure peaks are discussed.

Crystallization and melting are investigated in blends involving bacterial poly($ beta$-hydroxyalkanoates), PHA's. Two different blend systems are investigated. The first comprises bacterial, isotactic poly($ beta$-hydroxybutyrate), PHB, blended with synthetic, atactic PHB. The second is composed of bacterial poly($ beta$-hydroxyvalerate), PHV, blended with poly($ beta$-hydroxybutyrate-co-hydroxyvalerate), P(HB-co-HV), and bacterial PHB. / Crystallization kinetics are measured for isotactic/atactic PHB blends. The atactic component is shown to depress the spherulitic growth rate of the isotactic PHB. The Lauritzen-Hoffman model is used to analyze the crystallization data. A regime II $ to$ III transition is observed at a constant temperature of 140$ sp circ$C in the blends. The ratio of nucleation constants for the two regimes, K$ rm sb g sp{III}$/K$ rm sb g sp{II}$, is found to deviate from the theoretical value of 2.0 in the blend system. Equilibrium melting points are measured for the isotactic component and are found to be depressed by the atactic component. The Nishi-Wang equation is used to obtain an interaction parameter, $ chi sb{12}.$ Multiple melting of isotactic PHB is reported and analyzed. It is shown that a melt/recrystallization process is operative and a model is proposed to explain the melting behaviour in terms of recrystallization and annealing effects. / Crystallization kinetics of bacterial PHV are analyzed using the Lauritzen-Hoffman model. Crystallization is shown to occur in regime II. The equilibrium melting point of PHV is measured to be 130$ sp circ$C. A blend of PHV with P(HB-co-HV) of 77 mol% HV is shown to exhibit cocrystallization. The homopolymers PHB and PHV are shown to be phase-separated in the melt, thus precluding cocrystallization.

The present study is devoted to the morphologies and corona compositions in aggregates of mixtures of PS-b-PAA and PS-b-P4VP block copolymers as influenced by controllable assembly parameters, such as block length, pH, solvent, water content and the molar ratio of PAA/P4VP. Morphologies and surface properties of the aggregates were investigated by transmission electron microscopy and electrophoretic mobility, respectively. According to the results, the general hypothesis that the external corona is composed of long chains, while short chains form the inner corona of the vesicles, is valid only in mixtures without additives (no acid or base). In the presence of acid or base the environment during aggregate formation influences the system. Besides the numerical block length, pH and solvent composition, and therefore solubility, determines the morphology and the coil dimension; the numerically longer chains can be made to contract and to go to the inside, while the numerically shorter chains go to the outside.

The self-assembly behavior of poly(ethylene oxide)-b-polystyrene- b-poly(acrylic acid) (PEO-b-PS-b-PAA) triblock copolymers in solution is the focus of this thesis. The triblock copolymers were synthesized by atom transfer radical polymerization (ATRP). The compositions of the block copolymers were determined by 1H NMR. The synthesized block copolymers have relatively low polydispersity indexes (PDI < 1.3) as proved by GPC. The influence of several factors on the ATRP of styrene or t-BA, such as temperature, catalyst and polymerization time, was also explored. The effects of several parameters on the self-assembly behavior of this triblock copolymer were investigated, including the nature and composition of the common solvent, PAA block length, pH, water content, and initial copolymer concentration. Multiple morphologies, such as spheres, vesicles, lamellae and rods have been prepared by varying the above parameters. In particular, vesicles with either PEO or PAA outside have been successfully prepared in dioxane/water. These vesicles may serve as carriers for potential encapsulation applications. The average size and corona chain composition of the triblock copolymer vesicles can be controlled by varying factors such as the PAA block length and pH. The polymer chains may have different arrangements in the vesicle wall, resulting in different corona chain compositions. The vesicles with PAA outside are stable in water, while the vesicles with PEO outside tend to flocculate. Nevertheless, the sediment can be redispersed under vigorous stirring.

Dendrimers find applications in many diverse fields including biology, catalysis, the pulp and paper industry, etc. The distinctive properties of dendrimers leading to their wide applicability include tailorability and high surface group density. In this thesis the design and synthesis of water soluble dendrimers for potential applications as anti-scalants and bactericides, two important areas within the pulp and paper industry, are explored. The dendrimers were constructed on a tetrafunctional core which allows us to obtain a higher number of end groups at a lower generation than in the bi- and trifunctional cores generally employed. We utilized "click" chemistry, or more specifically the copper(I)-catalyzed alkyne-azide cycloaddition (CuAAC) reaction, for both dendrimer synthesis and post-functionalization. The implementation of this methodology required the selection of appropriate acetylene- and azide-terminated building blocks. For this purpose we chose i) an acetylene-terminated molecule having a carboxylic acid end group; and ii) an azide-terminated building block with a diol group at its other end. Using a divergent synthetic methodology in which the azide unit was first linked to the tetrafunctional acetylene core, followed by an esterification with the carboxylic acid group of the acetylene-terminated building block, we constructed acetylene-terminated dendrimers of generations 1-3. Generations 0-2 with terminal acetylene groups were subsequently functionalized with cationic amino groups for an evaluation of their behaviour as bactericides, and phosphonate groups for potential application as anti-scalants. The cationic amino-functionalized dendrimers, G0-NH3+, G1-NH3+ and G2-NH3+, as well as one of the OH-terminated dendrimers, G1, were then evaluated for their bactericidal efficacy. The generation one dendrimer, G1-NH3+, was found to be the most effective bactericide. Additionally it was determined to be more potent than several previously studied dendrimers. The deprotection of the phosphonate-terminated dendrimers from their ethyl esters to the corresponding alcohols was found to be cumbersome, and prevented their evaluation as anti-scalants. / Les dendrimères sont utilisés dans plusieurs domaines scientifiques incluant la biologie, la catalyse, l'industrie papetière, etc. Les aspects uniques des dendrimères qui permettent cette application diverse sont leur haute densité de groupements en périphérique et la capacité de les adapter au besoin. Cette thèse abordera les sujets de l'élaboration et de la synthèse de nouveau dendrimères qui sont solubles à l'eau et qui pourraient être utilisés pour l'inhibition de l'entartrage et comme bactéricide, deux applications indispensables dans l'industrie papetière. Les dendrimères présentés dans ce manuscript ont été construits à partir un noyau tetra-fonctionnel, ce qui permet d'obtenir un plus grand nombre de groupes en périphérique qu'avec les noyaux bi-fonctionnels et tri-fonctionnels qui sont employés habituellement. La chimie « click », soit la réaction de cycloaddition entre un alcyne et un azoture, catalysée par le Cu(I), a été utilisée pour synthétiser les dendrimères. Pour exécuter cette démarche, le choix d'alcynes et d'azotures appropriés a été essentiel. A cet effet, nous avions choisi i) une molécule contenant un terminus acétylénique et un acide carboxylique à son autre extrémité ; ii) une molécule comprenant un azoture à une extrémité et un diol à l'autre extrémité. A l'aide d'une méthode divergente où l'azoture est d'abord lié au noyau acétylénique tetra-fonctionnel, suivi d'une estérification avec le groupement acide carboxylique du bloc moléculaire i), nous avons construit des dendrimère de génération 1 - 3 incorporant des acétylènes terminaux. D'autres dendrimères de générations 0 - 2 possédant des acétylènes terminaux ont été munis d'amines cationiques afin d'évaluer leur potentiel comme bactéricide. De même, ces dendrimères ont été aussi munis d'acides phosphoniques afin d'évaluer leur capacité d'inhibition de l'entartrage. L'efficacité comme bactéricide de ces dendrimères fonctionnalisés d'amines cationiques, G0-NH3+, G1-NH3+ et G2-NH3+, ainsi qu'un des dendrimères terminant en OH, G1, a été ensuite évaluée. Le dendrimère de génération un: G1-NH3+ a été le meilleur à cet égard. De plus il est le plus puissant que plusieurs autres dendrimères téstés dans le passé. La déprotection des dendrimères avec des acides phosphoniques ên surface pour les transformer en alcools n'a pas eu lieu, alors l'évaluation de leur efficacité en inhibition d'entartrage n'a pas été réalisé.

The behaviour of neutral, linear polymers in colloidal systems was studied. / The rate and reversibility of polymer adsorption were determined from changes in the hydrodynamic radius of the substrate latex by photon correlation spectroscopy (PCS). / Flocculation of latex was studied with respect to polymer and electrolyte concentration using stopped-flow turbidimetry and PCS. The observed optimal surface concentration and capture efficiency were compared with theoretical estimates. Self-reversing flocculation was seen in some cases involving non-equilibrium adsorption. / The forces between pairs of sterically stabilized spheres colliding in shear flow were determined from analysis of the particle trajectories. Impingement of the polymer layers was not extensive. A simple model demonstrated that drag due to fluid drainage through the adsorbed layers may contribute significantly to steric interactions in flow. / Particle deposition measurements indicated that adsorption of polymer onto glass from stagnation point flow is lower than diffusion controlled adsorption at the plateau value.

This thesis describes a study of the effect of microstructure on the thermal stability of poly(vinyl chloride), PVC, vinyl chloride-ethylene, VC-E, and vinyl chloride-propylene, VC-P, copolymers obtained by chemical modification of PVC. The VC-E copolymers, with an ethylene content between 1.1 and 21 mole %, are random copolymers with approximately the same degree of polymerization as the original PVC. A decrease in the number of defect sites is observed with extent of reaction. Concomitantly, the syndiotacticity increases. The VC-P copolymers, with propylene content of ca. 0.1%, also have less labile chlorines than the homopolymer since these react preferentially. / The thermal stability of solid state samples was studied, at temperatures between 150 and 190$ sp circ$C under a nitrogen atmosphere, using a conductimetric method to measure evolved HCl. The thermal stability of the modified samples is improved relative to that of the initial homopolymers. For the VC-E copolymers, a linear relationship is observed between the rates of degradation and the number of labile chlorines, total double bonds and the degree of syndiotacticity. The role of syndiotacticity on the thermal degradation behavior is confirmed in results obtained with two unmodified PVC samples, with a similar number of defect sites but different syndiotacticity. The more syndiotactic resin shows a higher thermal stability. The average polyene sequence length is independent of the ethylene concentration. Thus, the ethylene units do not interfere in the development of polyene sequences. / The VC-P copolymers also show improved thermal stability as compared to that of PVC. However, the improvement is less than that of the VC-E copolymers, due to a lower extent of substitution of labile sites. / PVC previously saturated with HCl shows a markedly increased rate of degradation reflecting the autocatalytic role of HCl. For the PVC coated samples, a decrease in the degradation rates with decreasing PVC film thickness is observed due to more efficient removal of HCl. The PVC mixtures with Chromosorb W or silica gel exhibit a decrease in the dehydrochlorination rate constants with decreasing PVC content. The inert substrate acts as a diluent and avoids agglomeration of the samples and thus facilitates the removal of HCl.

The first part of this research concerns gelation in reversible gels. On the basis of calorimetric, viscometric, and spectroscopic results, a novel mechanism of gelation is described. It is proposed that the formation of the gel network leads to an increase in entropy which is sufficient to overcome the unfavorable gelation enthalpy. Gelation is, therefore, said to be entropy driven. The role of the solvent in the gelation process is also discussed. / The second part of the research is a study of spherulitic growth rate in blends of isotactic polypropylene (iPP) and a compatibilizer. Using time-lapse photomicroscopy it was found that addition of small amount of compatibilizer can enhance the growth rate of iPP. Similar results were obtained with chemically modified compatibilizers. The enhancement is explained in terms of partial miscibility between iPP and compatibilizers. A mathematical model of the kinetics of spherulitic growth rate in partially miscible blends is described.