A cantilever based sensor system was adapted to characterize the photo-mechanical effect in thin films of azobenzene based polymers coated on silicon and mica cantilevers. The photomechanical effect is defined as a reversible molecular shape change upon absorption of light, resulting in a significant mechanical macroscopic deformation of the host material. The sensor was used to calculate cantilever bending, changes in surface stress, photo-mechanical energy, efficiency, and energy per unit volume for the polymers PDR1A, PDR13A and PMMA-co-PDR1A based on DR1 and DR12 dyes. The study demonstrated fast and significant cantilever bending as well as a robust, repeatable, and measurable photo-mechanical effect for the polymers studied. PDR1A exerted the largest forces and PMMA-co-PDR1A the greatest efficiency. This exhibits the ability of these thin polymer layers to act as strong light-driven 'artificial muscles' for larger mechanical systems, and the utility of the cantilever sensor platform for quantitative characterization of the photomechanical effect of azobenzene based polymers.While micron-scale surface mass transport and formation of surface relief gratings in azobenzene polymers is a well-known phenomenon, a complete understanding of the underlying mechanism has yet to be achieved. Nanoindentation experiments were conducted to elucidate the changes in mechanical properties of PDR1A, a well-known covalent side-chain azo polymer and P4VP(DY7)0.5, a hydrogen-bonded polymer-azobenzene complex, under irradiation. Material creep was characterized by calculation of the strain rate sensitivity m, of the two polymers for the dark and illuminated states. The experiments show a significant change in material creep between the dark and illuminated states of both materials. The measured strain rate sensitivity m increases from 0.021 to 0.038 (81%) for PDR1A and 0.086 to 0.192 (123%) for P4VP(DY7)0.5 between the dark and illuminated states respectively. The correlation of experimental data describing photo-induced softening to the structure-property relationships of the two materials and their implications to understanding surface mass transport in azobenzene based materials is discussed. / Un système de détection utilisant un micro-lévier fut adapté pour caractériser l'effet photomécanique dans des couches mince de polymères contenant de l'azobenzène sur des micro-lévier fabriqués de silicium et mica. L'effet photomécanique est défini comme un changement réversible de la forme moléculaire lors de l'absorption de la lumière, ce qui entraîne une déformation importante mécanique macroscopique du matériel. Ce capteur a été utilisé pour calculer la flexion du micro-lévier, les changements dans la tension de surface, l'énergie photomécanique, l'efficacité du système et l'énergie capté par unité de volume pour les polymères PDR1A, PDR13A et PMMA-co-PDR1A basé sur les chromophores DR1 et DR12. L'étude a démontré une flexion rapide ainsi que robuste du micro-lévier, basé sur des mesure reproductible photomécanique pour les polymères étudiés. Nous avons trouvé que les polymères PDR1A exercent la plus grande force et PMMA-co-PDR1A la plus grande efficacité. Ceci démontre la capacité de ces couches minces de polymères à agir en tant que «muscles artificiels» pour des systèmes mécaniques macroscopique, et l'utilité de la plate-forme du capteur micro-lévier pour la caractérisation de l'effet photomécanique des polymères à base d'azobenzène.Bien que le transport de masse micrométrique et la formation des reliefs de surface dans les polymères d'azobenzène est un phénomène bien connu, une compréhension complète du mécanisme que mène a ceux-ci n'a pas encore été atteint. Des expériences de nanoindentation sous irradiation ont été menées pour élucider les changements dans les propriétés mécaniques de PDR1A, un polymère bien connu avec des chaînes latérales azoïques et P4VP(DY7)0,5, un polymère complexé à l'aide de liens d'hydrogène. Du fluage de ces matériaux a été caractérisé par le calcul du rapport de la sensibilité de déformation (m) de ces deux polymères pour les états sombres et lumineux. Les expériences montrent un changement significatif du fluage des polymères entre les états sombres et lumineux de ces deux matériaux. Le taux de la sensibilité de déformation (m) mesuré augmente de 0,021 à 0,038 (81%) pour PDR1A et de 0,086 à 0,192 (123%) pour P4VP(DY7)0,5 entre les états sombres et lumineux, respectivement. La corrélation des données expérimentales décrit l'adoucissement photo-induit basé sur les relations structure-propriété des deux matériaux, leurs implications pour la compréhension du transport de masse pour les matériaux à base d'azobenzène sont discutées.

Owing to its unique structure, along with the inexhaustible renewability, cellulose has been a subject of scientific and commercial interest for over 150 years. However, given attractive structural properties, such as stiffness, hydrophilicity, stereoregularity, potential for chemical modifications and ability to form superstructures, utilization of this biopolymer is far below its potential. Over the past few years the number of research projects to modify cellulose fibers to make them more suitable for numerous applications has increased. Transforming hydrophilic cellulose fibers into hydrophobic, non-hygroscopic fibers could potentially lead to a variety of new products, such as flexible packaging, self-cleaning films and strength-enhancing agents in polymer composites. To achieve this, we choose two different routes to chemically modify the cellulose fibers. In first method, cellulose fibers were oxidized with peridoate oxidation to different extent to prepare reactive dialdehyde cellulose (DAC) derivatives. Because introducing too many charge groups leads to fiber disintegration, we decided to cross-link the fibers to prevent this. These DAC fibers were in turn successfully cross-linked with 1,12-diaminododecane using methanol as solvent. Next, the cross-linked fibers were amidated in another Schiff-base reaction with n-butylamine to introduce the hydrophobic non-polar aliphatic chains. The cross-linked fibers exhibited stronger structural stability and the fibers did not disintegrate upon further alkylation with butylamine. The fibers were characterized with FTIR, 13 C-NMR, SEM, TGA, X-ray, contact angle and water sorption measurements. This procedure yielded very hydrophobic fibers with contact angles as high as 145o. Moreover, they had very low moisture uptake and high thermal strength, which makes them suitable for many potential products specially to be used in composites. The second method was based on intermediate carboxymethylation of cellulose with monochloroacetic acid, followed by subsequent substitution with an amine. The carboxylmethylated cellulose fibers (CCF) were cross-linked in an EDC assisted bioconjugation reaction with adipic acid anhydride (ADH). In order to alkylate the fibers and introduce aliphatic amine chains to the cross-linked fibers, a second carboxymethylation reaction was performed to introduce more charge groups to the cross-linked fibers to act as reactive sites for further alkylation reaction with butylamine. The resulting carboxymethylated cross-linked fibers were then reacted with n-butylamine to introduce non-polar aliphatic amine chains. The modified fibers were characterized by a variety of techniques, such as conductometric titration, infrared spectroscopy (FTIR), scanning electron microscopy (SEM), mechanical properties such as tensile strength and Young's modulus, water contact angle and water vapor transition rate (WVTR) measurements. / Grace à sa structure unique et son renouvellement quasi-inépuisable, la cellulose a été un sujet d'intérêt scientifique et commercial depuis plus de 150 ans. Toutefois, avec ses propriétés structurelles fascinantes, telles la rigidité, l'hydrophilie, la stéréorégularité, le potentiel de modifications chimiques et la capacité à former des superstructures, l'utilisation de ce biopolymère est bien en deçà de son potentiel. Au cours des dernières années, la recherche visant à modifier les fibres de cellulose pour les adapter à de nombreuses applications a augmenté. La transformation de fibres cellulosiques hydrophiles en fibres hydrophobes et non-hygroscopiques pourrait potentiellement mener à une variété de nouveaux produits, tels que des emballages flexibles, des films autonettoyants et des agents qui augmentent la résistance des composites polymériques. Pour atteindre ce but, nous avons choisi deux voies différentes pour modifier chimiquement les fibres de cellulose.Dans la première méthode, les fibres de cellulose sont oxydées à divers degrés par du periodate pour obtenir un dérivé réactif, le dialdéhyde de cellulose (DAC). Parce que l'introduction de beaucoup de groupements chargés mène à la désintégration des fibres, nous avons décidé, pour éviter cela, de réticuler les fibres. Les fibres de DAC ont donc été réticulées avec succès avec du 1,12-diaminododécane en utilisant du méthanol comme solvant. Ensuite, ces fibres réticulées ont été transformées en amides par une autre réaction de base de Schiff avec du n-butylamine qui a pour effet de greffer des chaînes hydrophobes aliphatiques non polaires. Les fibres réticulées se sont avérées avoir une stabilité structurel accrue et ne se sont pas désintégrées lors d'une alkylation plus poussée avec du butylamine. Les fibres ont été caractérisées par FTIR, 13 C-RMN, MEB, TGA, diffractométrie par rayons X, mesures de l'angle de contact et de sorption d'eau. Cette procédure a donné des fibres très hydrophobes avec des angles de contact plus élevés que 145o. De plus, elles ont une absorption d'humidité très faible et une résistance thermique élevée, ce qui les rend potentiellement adaptables à des usages dans de nombreux produits et tout spécialement dans les produits composites.La seconde méthode est basée sur la carboxyméthylation intermédiaire de la cellulose avec de l'acide chloroacétique, suivie d'une substitution ultérieure avec une amine. Les fibres de cellulose carboxyméthylées (CCF) ont été réticulées par une réaction de bioconjugaison classique utilisant l'EDC et l'anhydride d'acide adipique (ADH). Une seconde réaction de carboxyméthylation est alors effectuée sur les fibres réticulées pour y introduire plus de groupements chargés qui pourrons ensuite servir de sites réactifs pour une réaction d'alkylation. Cette réaction est accomplie avec du n-butylamine et a pour résultat la greffe de chaînes non polaires aliphatiques. Les fibres modifiées ont été caractérisées par une variété de techniques, telles le titrage conductimétrique, la spectroscopie infrarouge (FTIR), la microscopie électronique à balayage (MEB), les mesures de propriétés mécaniques telles la résistance à la traction et le module de Young, la mesure de l'angle de contact avec l'eau et la mesure du taux de transmission de la vapeur d'eau.

With their potentially extraordinary mechanical, thermal, and electrical properties, Single-Walled Carbon Nanotubes (SWNT)/polymer composites and composite fibers may be the ultimate building blocks for next generation ultra-light-weight, ultra-high performance structural applications. However, the dispersity and processibility of SWNT in polymer matrices have been a challenge because of the strong van der Waal attraction between individual nanotubes and their chemical inertness. Predicated on oleum's (100% H2SO 4 with excess SO3) ability to intercalate between individual SWNT inside SWNT ropes, two types of reinforcing SWNT with much improved solubility and dispersity in common solvents were developed: supra-roped SWNT (SWNT-R) and soluble, ultra-short (length<60 nm), carboxylated SWNT(US-SWNT). SWNT-R hold much improved dispersity in super acid and other solvents, and can facilitate the processing of SWNT/polylmer composites and composites fibers. US-SWNT exhibit up to 2 wt% solubility in common solvents. The availability of SWNT-R and US-SWNT open the opportunities for forming high performance composites, blends, and copolymers without inhibiting their processibility. Studies on the synthesis, processing, properties, and morphology of SWNT-R or US-SWNT/polymer composites and composite fibers have demonstrated the reinforcement efficacy of these SWNT in typical thermoset, thermoplastic and liquid crystalline polymer matrices. The epoxy composite system reinforced with 0.5--1 wt% of US-SWNT has shown an average 15% increase in tensile modulus and 50% increase in tensile toughness over those of the neat epoxy. A linear rule-of-mixture calculation indicates the high reinforcement efficiency of US-SWNT in epoxy matrix. The calculated SWNT's elastic modulus approaches the theoretical value. This processible and high performance US-SWNT/Epoxy resin may serve as a matrix material for advanced fiber composites. A novel solution-processing method was introduced to achieve good dispersion of SWNT-R or US-SWNT in Nylon (6, 6) matrix. In comparison to neat resin, increase in tensile modulus and glass transition temperature were observed with 5 wt% nanotubes incorporation. However, the tensile toughness was significant decreased. An advanced SWNT-R/US-SWNT poly(p-phenylene terephthalamide(PPTA) composite fiber system was developed to realize the ultimate SWNT properties and make them processible by conventional fiber spinning processes.

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.

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.