Surface and interaction characteristics of poly(styrene-b-4vinylpyridine) (S-4VP) and poly(styrene-b-methacrylic acid) (S-MAA) diblock copolymers were investigated by the method of inverse gas chromatography (IGC). Not surprisingly, the MAA segments were found to be acidic, while the polystyrene (PS) and the 4VP blocks were found to be basic, the 4VP moiety being the stronger base. For the S-4VP diblocks, when adsorbed onto particulates with acidic surfaces, the 4VP block is preferentially oriented to the substrate, leaving an air interphase which is enriched in PS. For the S-MAA diblock, at higher interphase thicknesses, the bulk and surface compositions became similar, and the interphases are non-isotropic with respect to local composition, and molecular conformation. For both diblocks, it was shown that the adsorbed layers form interphases in which the local composition varies with the adsorbed mass and the composition of the copolymer diblock. The effect was more pronounced when the strength of the acid/base interactions at the interface was increased. The experimental finding also permits the calculation of thicknesses for the adsorbed interphases (100-1000 A). / Proton nuclear magnetic resonance was used to determine the quantities of S-4VP diblocks in solution. In a selective solvent (toluene), it was found that surface interactions lead to preferential adsorption of the 4VP chain segments onto the particulates. Isotherms show that there is a direct correlation between the normalized equilibrium quantities of adsorbed copolymer diblocks and the length of the 4VP anchor. A linear relationship also was obtained between the equilibrium quantities per unit area of substrate, and the acid/base properties of the particulates. Using a published scaling model, good agreement was found between the experimental and predicted equilibrium quantities of adsorbed material. For these systems, it was demonstrated that the prefactor of the scaling law relation was directly related to the acid/base properties of the substrate, as expressed by the values of the acid/base surface indices obtained by IGC. / Composites based on PS and polychloroethylene were analyzed by dynamic mechanical thermal analysis and differential scanning calorimetry methods. The composites were formulated with four loading levels (2, 5, 20 and 35 wt %) of uncoated and coated (S-4VP modified) particulates. A chain overlap region at the boundary of the particulate was determined. The extent of this region was found to increase in parallel with the PS diblock segments, and with favorable acid/base interactions between the composite constituents.

Polystyrene-b-poly(acrylic acid) block copolymers can self-assemble in selective solvents to form aggregates of different morphologies, including spherical micelles and vesicles. The ability of spherical micelles to solubilize (incorporate) 2-nitrodiphenylamine, a model hydrophobic but polar dye molecule, is investigated. The solubilization capacity of the micelles is evaluated as a function of the dye concentration, and the results are explained by treating solubilization as an adsorption process. The location of the incorporated molecules within the micelle is also examined, and the interfacial region of the micelle is identified as the solubilization site. Vesicles prepared from polystyrene-b-poly(acrylic acid) in dioxane/water mixtures undergo fusion (and therefore increase in size) as the water content in the solvent mixture increases. The kinetics of this process is followed, and the evaluated relaxation times range between 10 and 700 s, depending on the solvent composition, the amount of water added, the polymer concentration, and the poly(acrylic acid) block length. In addition, the preparation of vesicles with tunable sizes is examined. Additives (such as NaCl, HCl, and NaOH), as well as the solvent composition (ternary mixtures of water/dioxane/THF) are used to vary the diameter of vesicles prepared from the same copolymer. The effect of poly(acrylic acid) block length on vesicles size is also determined. Finally, polystyrene- b-poly(acrylic acid) vesicles are used as model carriers for the anti-tumor drug, doxorubicin hydrochloride. A pH-induced, active loading method is applied to concentrate the drug into the aqueous cavity of the vesicles.

Controlled free radical polymerization is attractive as it produces polymers with well defined microstructures typically associated with “living” polymerization methods, using a wide range of monomers required for applications such as nanoporous membranes and barrier materials. Poly(trioctylammonium p-styrenesulfonate) homopolymer (poly(SS-TOA)) and poly(SS-TOA-ran-styrene) copolymers were synthesized by nitroxide-mediated polymerization (NMP) using an N-tert-butyl-N-[1-diethylphosphono-(2,2-dimethylpropyl)] nitroxide (SG1) based unimolecular initiator, called BlocBuilder. Polymerizations were controlled for low theoretical molecular weight at complete conversion (Mn,theoretical = 20 kg·mol-1), resulting in very low polydispersities (Mw/Mn < 1.1) and a linear increase in number average molecular weight, Mn, up to ≈ 35% conversion. SS-TOA was effective as a controlling co-monomer for the gradient polymerization with glycidyl methacrylate, using a N-succinimidyl ester modified BlocBuilder (NHS-BlocBuilder), which resulted in a relatively narrow molecular weight distribution (Mw/Mn = 1.43) and linear increase in Mn versus conversion. Poly(styrene-ran-acrylonitrile) (poly(S/AN)) and poly(tert-butyl methacrylate-ran-acrylonitrile) (poly(t-BMA/AN)) were also synthesized by NMP using BlocBuilder and NHS-BlocBuilder. In both systems, the polymers exhibited narrow, monomodal molecular weight distributions with relatively low polydispersities (Mw/Mn = 1.14-1.50), characteristic of a controlled polymerization. Mn versus conversion (X) plots were all relatively linear (Mn = 14.8-18.1 kg.mol-1, X = 40-70%) suggesting that “pseudo-living” behaviour was approached in the range of conversions studied. / Cette étude se concentre sur le thème de la polymérisation radicalaire contrôlée qui est attrayante de par sa facilité à produire des polymères avec une microstructure bien définie et demeure semblable à la polymérisation ionique/vivante. Elle présente l'avantage de permettre la génération d'une vaste gamme d'application de monomères allant des membranes nanoporeuses aux matériaux barrières. Le poly(trioctylammonium p-styrènesulfonate) (poly(SS-TOA)) et poly(SS-TOA-ran-styrène) ont été préparés par la polymérisation contrôlée par des nitroxydes, à base de la nitroxyde N-tert-butyl-N-[1-diéthylphosphono-(2,2-diméthylpropyl)] (SG1), aussi appelé BlocBuilder. La polymérisation a été le mieux contrôlée pour un faible poids moléculaire théorique (20 kg·mol-1 versus 45 kg·mol-1), avec de très basses polydispersités (Mw/Mn < 1.1) et une croissance linéaire du poids moléculaire moyen en nombre jusqu'à une conversion de ≈ 35%. Le SS-TOA à également prouvé son efficacité comme contrôleur comonomèrique pour la polymérisation de type gradient avec le méthacrylate glycidyl, accompagné d'une forme protégée de BlocBuilder (achevés de N-succinimidyl, appelé NHS-BlocBuilder). Le Poly(styrène-ran-acrylonitrile) (poly(S/AN)) et poly(tert-butyl méthacrylate-ran-acrylonitrile) (poly(t-BMA/AN)) ont également été copolymérisés par polymérisation contrôlée en employant des nitroxydes avec les initiateurs BlocBuilder et NHS-BlocBuilder. Les deux systèmes ont démontré un bon degré de contrôle : une distribution de poids moléculaire étroite avec des polydispersités relativement faibles (Mw/Mn = 1.14-1.50) combinée à une croissance linéaire du poids moléculaire moyen en nombre avec une conversion (X) relativement élevée (Mn = 14.8-18.1 kg.mol-1, X = 40-70%). Ces résultats confirment bien la notion de "copolymérisation pseudo-vivante".

The formation of crew-cut aggregates from polystyrene-b-poly(acrylic acid) (PS-b-PAA) copolymer in low alkanols (methanol, ethanol, iso-propanol and n-butanol) was investigated. The block copolymer employed has 390 PS units and 79 PAA units. The copolymer is solubilised upon heating and micellisation occurs as the temperature decreases: this preparation is referred to as the single-solvent method. Temperatures reached are above 120°C and thus require the use of pressure reactors as low alkanols have low boiling points. Three types of reactors were employed. The first was the unstirred reactor which validated the method. Secondly, a stirred reactor was used in order to maximise the dissolution of the copolymer over a broader range of conditions that achieved in the unstirred reactor. Micellisation induced on cooling is explained as being analogous to that encountered on adding a precipitant to a copolymer solution. The effects of stirring and pressure are also discussed. / Various morphologies were obtained in both reactors, including a highly ordered bicontinuous morphology in the stirred reactor. To determine the thermodynamics of the micellisation at high temperatures and elevated pressures, a reactor with windows was acquired. The set-up, interfacing and development of a more advanced instrument including this windowed reactor are described. Preliminary experiments showed that in-situ turbidity measurements can be carried out on this instrument; the results of these studies are also briefly reported. Finally, preliminary light scattering studies of polycaprolactone- b-poly(ethylene oxide) (PCL-b-PEO) copolymers of different compositions have been carried out. The dependence of the critical water content (cwc) on copolymer composition and concentration was studied and the results described.

Azobenzenes can undergo photoisomerization, therefore systems incorporating these chromophores present light-switchable properties. The reversible photoisomerization from the trans to the cis form is accompanied by several changes at the molecular level. Differences in the absorption spectrum, polarity and structure between the two isomers have been used in various systems to fine-tune other properties of these systems with light. The present work reviews physical properties that can be photomodulated in polymers functionalised with azobenzenes. Emphasis is put on electric and magnetic properties, structural changes, surface properties, binding activity, complexation, stereochemistry, ion permeability and enzyme activity. The second part of the thesis details experimental investigations about the photoresponsive behaviour of thin films of polyelectrolytes containing azobenzenes. Namely, poly(allyl amine hydrochloride) was self-assembled with a synthetic random copolymer of acrylic acid and disperse red 1. (Abstract shortened by UMI.)

Aggregate morphologies as a function of apparent pH (PH*) have been studied for PS-b-P4VP diblocks in DMF/H2O. The pH* changes are induced by addition of HCl or NaOH (100 nM to 20 mM). As the pH* increases, the morphology changes from large compound micelles to a mixture of spheres, rods, and vesicles, to spheres, to rods, back to spheres when no acid or base is added, then to rods again, back to spheres again, and finally to a mixture of spheres, rods, lamellae, and vesicles. The interplay of the charge introduction into the corona chains, shielding, and steric-solvation interaction is responsible for the complex behavior. The effect of NaCl on the neutral copolymer and the effect of pH* on a quaternized copolymer are also explored. / Thermodynamics of micellization of PS-b-PAA copolymers in DMF/water have been investigated as a function of four variables, i.e. the water content, PS block length, PAA block length, and NaCl concentration. Based on a closed association model, thermodynamic functions (DeltaG, DeltaH, and DeltaS) are estimated. / Morphological phase diagrams, as well as kinetics and mechanisms of the rod to vesicle transition for PS-b-PAA diblocks in dioxane/water have been studied. In the study of morphological phase diagrams, the regions of stability are identified for spheres, spheres and rods, rods only, rods and vesicles or rods and bilayers, vesicles or bilayers alone, and for some copolymers, more complex mixtures. Evidence is presented that spheres, rods, and vesicles represent true equilibrium structures. The influence of the water content and polymer concentration on aggregate morphologies and the effect of fractionation on the phase diagram are discussed. The block length dependence of the phase diagram is also explored. It is found that copolymers with long core-forming blocks favor the formation of vesicles, and that for copolymers with short core-forming blocks, vesicles are favored at high water contents and other bilayers at relatively low water contents. In the kinetic and mechanistic study, two consecutive first order relaxation processes are found. In the first, the rod is flattened and then converts to a lamella, while in the second, the lamella closes to form a vesicle. Two relaxation times are explored in terms of the initial water content, size of the jump in the water content, and polymer concentration.

We describe our investigations into photochemical and micro-structural characteristics of sol-gel derived silica-methacrylate composites (SAC). Upon irradiation with UV light, thin SAC films undergo spatially localised increases of the index of refraction, a macroscopic property that has been used in the photo-lithography of passive integrated optics devices. Our spectroscopic studies indicate that UV initiated free-radical polymerisation of methacrylate substituents trigger further growth and densification of the silica host. This advances our molecular level understanding of photo-reactions in hybrid organo-silica networks. / We examine laser-initiated organic chain growth in SAC planar waveguides. Optical modes initiate polymerisation of methacrylate substituents along the propagation path. In turn, the nascent reaction medium presents a non-uniform refractive index profile to the guided laser beam. Spatially localised and intensity-dependent refractive index changes create a lens-like profile in the medium. As a result, the beam self-focuses along its propagation axis without diffraction. / We describe oriented organic chain growth in the nonlinear optical and highly anisotropic reaction field provided by a linearly polarised, self-focusing laser beam. A self-focusing laser beam induces an anisotropy in the refractive index profile of SAC waveguides. We characterise laser-induced birefringence in the hybrid network through polarised waveguide Raman spectroscopy and optical birefringence measurements. / Long-range periodic self-organisation in sol-gel derived silica acrylate composites formed in the absence of external templates was observed for the first time. Significantly, the periodicity associated with this structure is approximately 200 nm, approaching the optical wavelength regime.

Suspensions of cellulose nanocrystals may be prepared by hydrolysing wood pulp or cotton filter paper with sulfuric acid. Due to the rod-like shape of the nanocrystals, these aqueous suspensions display liquid crystalline behaviour. This thesis examines these unique suspensions at three different concentration ranges. At low cellulose concentrations the suspensions are disordered, becoming ordered upon reaching a critical concentration, which depends on the aspect ratio of the rods. AFM and TEM were used to characterize particle size and polydispersity. Just beyond the critical concentration for anisotropic phase formation is an intermediate concentration range in which the isotropic and anisotropic phases co-exist. This biphasic region was examined for its potential to partition dextran molecules. At extremely high cellulose concentrations, solid cellulose films that maintain some chiral nematic order may be obtained. The degree of order in the films has been measured using induced circular dichroism and optimized by magnetic alignment. These suspensions can also be used to create model surfaces of cellulose I. The smooth cellulose surfaces have been characterized by XPS, X-ray diffraction, and AFM.

Four novel aromatic difluoride compounds were synthesized for use as monomers in nucleophilic aromatic displacement polymerization reactions. Attempts were then made to polymerize these monomers with a series of bisphenols, using potassium carbonate as a base, in a dipolar aprotic solvent as in equation 1. eqalign qquad{& rm K sb2CO sb3 cr rm F{-}Ar{-}F + HO{-}Ar{-}OH quad& rm quad longrightarrow quad quad bigl(O{-}AR{-}O{-}Ar bigr) sb{n} cr& rm Dipolar aprotic cr& rm solvent cr& rm 160-195 sp circ C cr} eqno(1) sing the reaction above, several novel poly(aryl ether)s have been produced and some of their physical properties, such as glass transition temperature and thermal stability, have been investigated. The polymers all contain nitrile groups which have potential to form cross-links upon heating, thereby increasing the use temperature and solvent resistance of the resulting materials. This cross-linking potential was investigated. Also, polymers containing the 9,10-dicyanophenanthrene moiety were prepared and then reacted with cuprous chloride and phthalonitrile to give poly(aryl ether)s containing copper phthalocyanine groups.

The origin of the gel formation in dilute solutions of ultra high molecular weight polyethylene (UHMWPE) is the subject of this thesis. At low heating rates v, 0.5 12 K/h, it cannot be detected in the usual DSC runs made at v = 600 K/h or higher. / The crystallinity found including fraction (III) (0.84-0.94) upgrades the calorimetric crystallinity to the values found by techniques not involving melting. Arrested melting which occurs between fractions (II) and (III) reveals the existence of a network whose cohesive junctions are unmelted and stabilized by strain. The amount of fraction (III) which is about 20% in the nascent sample increases to about a third of all crystals in a sample submitted to cycles of slow melting and slow crystallization. / Fraction (III) is stable in the presence of a solvent. However, its concentration in the sample can be made to vary between 5 and 25% by the appropriate choice of the solvent and thermal history. The network is stabilized during the dissolution of fraction (II) in decalin while it is reduced if the solvent is trichlorobenzene. Other thermal histories minimize the effect of solvent on the partition of the crystals between fractions (II) and (III). Crystallization in a temperature gradient is effective in diminishing fraction (III) and increasing fraction (II). A hypothesis to explain the high crystallinity of gels obtained by quenching is proposed. / The metastable states obtained during dissolution do not revert to the equilibrium state when the solvent is evaporated. Mechanical properties such as drawability and also the melting trace of the dried gels are affected by the solvent-induced changes in the melting pattern. The amount of fraction (III) appears to be a good test of drawability. / The dissolution traces at low v provide a much-needed quantitative characterization of UHMWPE gels, the crystals formed on quenching having a dissolution trace distinguishable from those grown isothermally or under shear. / Since fraction (III) results from a general process of melting, its occurrence in other polymers is expected and indeed has been found in preliminary experiments on poly-4-methylpentenel (P4MP1) and polypropylene (PP). (Abstract shortened by UMI.)