This work investigates the volume changes effected during multicomponent resin polymerization/crosslinking (cure shrinkage) in an effort to reduce or eliminate this phenomenon (zero-shrinkage polymerization). The systems under study contained: a polyfunctional monomer; a second, difunctional low-boiling monomer; and a thermoplastic polymer additive. These components are miscible forming a single (transparent) phase, which remains stable and shows the expected cure shrinkage in slow polymerization. Upon rapid cure (within 2-10 minutes) these systems undergo phase separation and show significantly reduced cure shrinkage, attaining zero shrinkage within certain composition ranges. Experimental evidence based on Scanning Electron Microscopy, polymerization under pressure, photopolymerization, and solvent extraction indicates that the reduction in cure shrinkage is due to the nucleation and growth of vapor bubbles of the low-boiling monomer within separate microdomains formed during rapid polymerization and precipitated by the high temperatures attained at peak exotherm, as well as negative hydrostatic pressures arising from cure shrinkage of the crosslinked polymer phase.

Polymer light-emitting electrochemical cells (LECs) are unique solid-state light-emitting devices operating on the principle of in situ electrochemical doping and the formation of a p-n junction. Compared to conventional polymer light-emitting diodes, LECs possess some favorable device characteristics, making them attractive candidates for flat panel display applications. However, the underlying operating mechanism of LECs has been the subject of intense scrutiny and debate. The extremely large planar devices demonstrated by Dr. Gao’s group offer an unparalleled spatial resolution for investigating the electrochemical doping process. With time-lapse fluorescence imaging, our group has demonstrated the existence of the electrochemical doping and the p-n junction in an operating LEC. However, the LEC electronic structure has never been adequately studied and understood. In this thesis, the original research on the electrical and optical scanning measurements on extremely large planar LECs is described. A fresh LEC film has, for the first time, been turned on to form a light-emitting p-n junction by biasing a pair of probes that form direct contacts with the LEC film. The quasi-one-dimensional probe tips allow insight into the electrochemical doping mechanism, without being disturbed by imperfections in the pre-deposited electrodes. Time-lapse fluorescence imaging has exhibited p- and n-doping of various shapes and shades, p-n junction electroluminescence, and the effects of bias reversal. The observed doping reaction kinetics suggests that n-doping is reaction-limited whereas p-doping is diffusion-limited. Furthermore, the electric potential and conductivity distributions of extremely large planar LECs have been mapped. The results show that the p-doping is more conductive than n-doping. More importantly, The results provide the first evidence that the p-n junction is indeed a graded one with decreasing conductivity and doping concentration from the electrode contact to the metallurgical junction. In addition, the optical beam induced current (OBIC) measurement has been explored to map the built-in electric field of extremely large planar LECs. This result clearly shows that a large electric field exists only around the junction region rather than in the electrode region. Moreover, the result confirms that the LEC electronic structure is a graded p-n junction. / Thesis (Ph.D, Physics, Engineering Physics and Astronomy) -- Queen's University, 2011-05-12 16:27:05.208

Correlations between the Oxygen Index (OI) and intrinsic polymer characteristics are researched. The goal is to establish a property matrix to aid design and evaluation of new polymers flammability and fire retardancy. Many researchers have independently correlated heat of combustion, char formation, halogen substitution, and polymer end groups to the OI. Other possible correlations are explored: oxidation potential defined for polymer repeat units gives inconclusive results. Electronegativity and bond strength approaches are also inconclusive. Obvious effects of hydrogen to carbon ratio, molecular mass or polymer density are verified but not easily modeled. The effects of polymer group contributions as well as products of incomplete combustion influence the OI but available data allows no valid correlation. This attempt to find a correlation has not yielded rewards. Further attempts should be undertaken in view of these results.

Styrene-dimethylsiloxane (S-DMS) di- and triblock copolymers, whose overall molecular weight ranged from 3,800 to 4.7 $\times$ 10$\sp5$, and styrene contents from 4 to 96%, were studied using differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy. Blends of the S-DMS diblock copolymer and PS homopolymer with PS weight fraction ranging from 0.04 to 0.96 for two different PS to S block molecular weight ratios, 30:1 and 1:50, were also studied by DSC. Comparisons of calculated and the experimental specific heat, C$\sb{\rm p}$, were made to estimate the relative error in C$\sb{\rm p}$ measurements and the percent mixing of block chains in their opposite microphase. The occurrence of DMS microphase crystallization depends on the DMS block molecular weight, but the degree of crystallinity depends both on weight percent of DMS and on the cooling rate. The critical DMS block molecular weight at which the DMS microphase crystallize under the experimental conditions used in this work is between 3,800 and 15,400. The glass transition temperature, T$\sb{\rm g}$, of fully amorphous DMS microphases is influenced by the overall composition of each sample. The T$\sb{\rm g}$ of semicrystalline DMS microphases is affected by the degree of crystallinity of the DMS microphases. The variation in DMS microphase T$\sb{\rm g}$ were attributed to a thermal stress effect. The number of styrene T$\sb{\rm g}$'s in each blend was used to characterize the mixing of PS and the S blocks. The weight fraction of styrene segments in each styrene phase was calculated from the heat capacity change at T$\sb{\rm g}$. In styrene phase separated blends, the weight fraction of each styrene phase varied with the annealing temperature. A phase diagram was constructed for the blends with 30:1 PS to S block molecular weight ratio.

It is generally accepted that in random styrene ionomers the ion-pairs tend to associate to form small aggregates termed multiplets which are embedded in the polymer and act as crosslinks. At sufficiently high ion-contents, ion-rich regions termed clusters are believed to phase-separate from the polymer matrix. In this study, the dynamic mechanical properties of random styrene ionomers containing various concentrations of alkali-metal methacrylate groups were measured over a range of temperatures at several different frequencies. Two peaks are evident in the loss tangent (tan $ delta)$ vs. temperature curves, indicating that the materials are phase-separated, with each tan $ delta$ peak resulting from the glass transition (T$ sb{ rm g})$ of a separate phase. This hypothesis is supported by the magnitudes of the apparent activation energies determined in this study for each transition. The relative heights and areas of the tan $ delta$ peaks indicate that the cluster phase becomes dominant at ion contents above ca. 6 mol %, and that complete phase inversion occurs at relatively low ion-contents. This finding, together with the results of small-angle X-ray studies performed elsewhere, led to the development of a new model for the morphology of random styrene ionomers. The model is based on aggregation of ion-pairs to form multiplets. Each ion-pair in a multiplet effectively anchors the polymer chain to which it is attached, thereby forming a layer of polymer with restricted mobility surrounding the multiplet. Isolated multiplets act as large crosslinks, thus increasing the glass transition temperature of the material. As the ion content is increased, the regions of restricted mobility surrounding each multiplet overlap to form larger contiguous regions of restricted mobility. When these regions become sufficiently large, they exhibit phase-separated behaviour and are termed clusters. The model is in good agreement with a very wide range of experimentally observed p

Over the last two decades, a large amount of research has focused on natural cellulose fibers, since they are "green" and renewable raw materials. Recently, nanomaterials science has attracted wide attention due to the large surface area and unique properties of nanoparticles. Cellulose certainly is becoming an important material in nanomaterials science, with the increasing demand of environmentally friendly materials.In this work, a novel method of preparing cellulose nanofibers (CNF) is being presented. This method contains up to three oxidation steps: periodate, chlorite and TEMPO (2,2,6,6-tetramethylpiperidinyl-1-oxyl) oxidation. The first two oxidation steps are investigated in the first part of this work. Cellulose pulp was oxidized to various extents by a two step-oxidation with sodium periodate, followed by sodium chlorite. The oxidized products can be separated into three different fractions. The mass ratio and charge content of each fraction were determined. The morphology, size distribution and crystallinity index of each fraction were measured by AFM, DLS and XRD, respectively. In the second part of this work, CNF were prepared and modified under various conditions, including (1) the introduction of various amounts of aldehyde groups onto CNF by periodate oxidation; (2) the carboxyl groups in sodium form on CNF were converted to acid form by treated with an acid type ion-exchange resin; (3) CNF were cross-linked in two different ways by employing adipic dihydrazide (ADH) as cross-linker and water-soluble 1-ethyl-3-[3-(dimethylaminopropyl)] carbodiimide (EDC) as carboxyl-activating agent. Films were fabricated with these modified CNF suspensions by vacuum filtration. The optical, mechanical and thermo-stability properties of these films were investigated by UV-visible spectrometry, tensile test and thermogravimetric analysis (TGA). Water vapor transmission rates (WVTR) and water contact angle (WCA) of these films were also studied. / Au cours des deux dernières décennies, une grande quantité de recherches ont portées sur les fibres de cellulose naturels, car ils sont «verts» et de matières premières renouvelables. Récemment, la science des nanomatériaux a attiré l'attention en raison de la gamme grande surface et les propriétés uniques des nanoparticules. La cellulose est en train de devenir un matériau important dans la science des nanomatériaux, à la demande croissante de matériaux écologiques. Dans ce travail, un nouveau procédé de préparation de cellulose nanofibres (CNF) est présenté. Cette méthode contient un maximum de trois étapes d'oxydation: oxydations au periodate, au chlorite et au TEMPO (2,2,6,6-tétraméthylpipéridinyle-1-oxyle). Les deux premières étapes d'oxydation sont étudiées dans la première partie de ce travail. La pâte de cellulose a été oxydée à des degrés divers par un à deux étapes d'oxydation au periodate de sodium, suivi par le chlorite de sodium. Les produits oxydés peuvent être séparés en trois fractions différentes. Le ratio de la masse et le contenu de charge de chaque fraction ont été déterminés. La morphologie, la distribution de la taille et l'indice de cristallinité de chaque fraction ont été mesurés par l'AFM, DLS et XRD, respectivement. Dans la seconde partie de ce travail, des CNF ont été préparés et modifiés dans diverses conditions, y compris (1) l'introduction de diverses quantités de groupes aldéhyde sur les CNF par oxydation au periodate, (2) les groupes carboxyle sous forme de sodium sur les CNF ont été convertis à leur forme acide par traitement avec un type d'acide résine échangeuse d'ions; (3) ces CNF ont été réticulés de deux manières différentes en employant dihydrazide adipique (ADH) en tant que cross-linker et soluble dans l'eau 1-éthyl-3-[3- (diméthylaminopropyl)] carbodiimide (EDC) comme agent activateur de carboxyle. Les films ont été fabriqués avec ces suspensions de CNF modifiés par filtration sous vide. Les propriétés optiques, mécaniques et la thermo-stabilité de ces films ont été étudiées par spectrométrie UV-visible, essai de traction et de l'analyse thermogravimétrique (TGA). Les taux de transmission de vapeur d'eau (WVTR) et l'angle de contact de l'eau (WCA) de ces films ont également été étudiés.

The objective of this study was to better understand the kinetics of competitive deposition between polyelectrolyte-coated particles and polyelectrolyte molecules occurring simultaneously on the same surface. / In the study with cationic polyethylenimine (PEI), increasing the polyelectrolyte concentration showed six regimes of particle deposition. In the first regime, no particle deposition was observed, since the quantity of adsorbed polyelectrolyte was less than sufficient to create an electrostatic attraction between the partly coated particle and the surface. In the second regime, a fast rate of deposition is observed, where all of the PEI is adsorbed for complete coverage of particles except for a very small concentration in solution. In the third regime, initially fast deposition is followed by a slowing down of the rate until no deposition occurs due to a competition between free PEI in solution with coated particles for sites at the surface. In the fourth regime, no deposition is observed, since the concentration of PEI is high enough to adsorb extremely quickly using up all the surface sites available, reversing their charge to positive, repelling coated particles. In the fifth regime, slow deposition is observed, since high PEI concentrations screen the electrostatic repulsion. In the sixth regime, no deposition is observed possibly due to steric stability. / In the study with an anionic polyelectrolyte, NaPSS (sodium polystyrenesulphonate), it was shown that the equilibrium adsorption was independent of molecular weight for molecular weights of 18,000 to 220,000. For these molecular weights, no conditions for sufficient electrostatic or steric repulsion between fully-coated particles and the surface was obtained to prevent deposition. The deposition is ascribed to the small polyelectrolyte layer thickness on TiO$ sb2$ and the collector surface, as well as electrostatic screening by salt. (Abstract shortened by UMI.)

A new simple method for the synthesis of novel hydroxy substituted 1,2-diphenylcyclopropanes was developed. Mono and dihydroxysubstituted-1,2-diphenylcyclopropanes were prepared by base-catalyzed decomposition of the corresponding hydroxy substituted 3,5-diphenyl-2-pyrazolines which were the products of the reaction between hydroxychalcones and hydrazine monohydrate. Some biphenols and activated aromatic difluorides containing the ethylene, chalcone and pyrazoline groups were prepared by novel, simple methods employing readily available starting materials and reagents. The monomers were used to prepare thermally cross-linkable polymers. New dianhydrides containing the 1,2-diphenylcyclopropane or diphenylacetylene group were synthesized from 1,2-bis(4-hydroxyphenyl)cyclopropane or bis(3-hydroxyphenyl)acetylene. / Subsequently, new types of poly(aryl ether sulfone)s, poly(aryl ether ketone)s, polyesters, polyformals, polyimides, poly(phenylene oxide)s and cyclic aryl ether oligomers containing the internal trans-1,2-diphenylcyclopropane, ethylene, chalcone, epoxide and 2-pyrazoline moieties were synthesized from these monomers by condensation polymerization reactions. Characterization of and cross-linking studies on these polymers were carried out utilizing DSC, TGA, TMA, GPC and NMR. The prepared polymers are high molecular weight, amorphous and soluble in common organic solvents. / The polymers can be thermally cross-linked. The glass transition temperatures of the polymers increased and their solvent resistance was improved significantly after curing. Thermogravimetric analyses showed that no significant weight loss accompanied the cross-linking reactions.

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.