Polymeric materials are increasingly being used in diverse, very demanding applications. Either pre- or post- application environments may require exposures to conditions hostile to the polymer's integrity. Frequently, these demanding conditions result in degradation of the polymer and subsequent decreases in desirable properties. Clearly then, a methodology to predict important properties, such as Tg, molecular weight, and tensile strength, from knowledge of the environmental history of a polymeric-based specimen is beneficial. The current study focuses on bisphenol A polycarbonate and tracks changes in the properties of this material as a function of the degree of degradation, t. For the purposes of the present research, the environmental effects have been limited to those associated with elevated temperature, although the methodology is general. This t parameter is a product of the kinetic rate constant, k, found from isothermal kinetics, and the time of degradation, t. Elucidation of t has been linked to measurement of the molecular weight distribution which in turn can be related to various properties to yield predictive relationships for these properties. Only the thermal history of the polymer and its initial properties are required for the model. This technique is not limited to a specific polymer or even to thermal degradation. As long as the kinetics of the process can be mathematically modeled, this approach should apply to a host of other situations, providing property prediction simply from knowledge of the material history. The research seeks to better understand the thermal degradation of polycarbonate. Kinetics of the process was explored, and the chemical mechanisms were examined. A key part of the project was the determination of the molecular weights and molecular weight distributions at each level of degradation. Furthermore, mechanical stress-strain properties, glass transition temperatures, and melt viscosities were also measured. This information, together with the kinetic expressions, facilitated prediction of these types of material properties for a known thermal history. / Ph. D.

The crystallization behavior of bisphenol-A polycarbonate (BAPC) was studied, focusing on the initial stage of crystallization and the secondary stage of crystallization. Bisphenol-A polycarbonate was the polymer chosen for this study because of its slow crystallization rate. With slow crystallization kinetics, the polymer morphology does not change when quenched below its glass transition temperature, enabling the study of different stages of crystallization through the frozen morphology. The study of the initial stages of crystallization pertained to crystallization times prior to the growth of detectable crystallinity. This study employed BAPC because of the long induction period, a direct result of the slow crystallization kinetics. During the induction period of polycarbonate crystallized at 190°C there was no evidence of polymer chain ordering that was seen in literature for other polymers. The length of the induction period determined by differential scanning calorimetry and wide-angle X-ray diffraction varied by over 6 hours because differential scanning calorimetry can detect a smaller amount of crystallinity than wide-angle X-ray diffraction. Signs of pre-ordering in the literature could be a result of experimental sensitivity. The study of the secondary crystallization dealt with the isothermal lamellar thickening of BAPC crystals during annealing, after crystallization for an extended period of time. Small-angle X-ray scattering and differential scanning calorimetry experiments were performed on bisphenol-A polycarbonate samples crystallized near 190°C for 8 days and annealed at either 223°C or 228°C for various times. The Gibbs-Thomson relationship, which can be defined using the experiments mentioned, yielded two thermodynamic constants, the equilibrium melting temperature and the surface free energy. Including data from literature in the determination of the constants, the equilibrium melting temperature and surface free energy of BAPC is 303°C and 36.6mJ/m2, respectively. Comparing the lamellar thickness measurements by small-angle X-ray diffraction with direct measurements by microscopy was difficult because the morphology of the polymer was not easily seen in the bulk using atomic force microscopy or scanning electron microscopy. Etching the sample was the most promising technique for future investigations of revealing the bulk morphology for direct lamellar thickness measurements. Crystallizing thin films of polycarbonate on calcite substrates allowed the measurement of lamellar thickness using scanning electron microscopy because the lamellae grow epitaxially to the substrate. The measurement of the long spacing in thin film samples was comparable to that of bulk samples. / Master of Science

Formaldehyde, an important feedstock in industrial processes and manufacture, is widely present in numerous consumer products. Emitted by many types of consumer products and indoor materials, indoor air can contain high concentrations of formaldehyde. Exposure to formaldehyde is hazardous to human health. Thus knowledge of formaldehyde mass-transfer properties is critical to efforts to reduce formaldehyde emissions and establish related standards and regulations. The primary objectives of this project include: 1) documenting and validating procedures and methods for analyzing and measuring formaldehyde mass-transfer characteristics; 2) evaluating and comparing formaldehyde mass-transfer properties in different materials using micro-balance sorption/desorption tests; 3) investigating observed formaldehyde mass-transfer irreversibility and the recently developed formaldehyde polymerization theory. The procedures and methods for analyzing and measuring formaldehyde mass-transfer characteristics were developed in an effort to minimize experimental variability and were strictly followed during the research. The formaldehyde mass-transfer properties of five polymer materials (polycarbonate, polystyrene, poly(methyl methacrylate), polyethylene and polypropylene) were measured through sorption/desorption testing. Results indicated that formaldehyde solubility was highest in polyethylene while the rate of diffusion was the highest in polypropylene. Results also showed that the diffusion process in the selected polymer materials was irreversible in all cases. Furthermore, additional testing showed no detectable polyformaldehyde formation on polymer surfaces after exposure to formaldehyde. The causes of observed mass-transfer irreversibility need further study. / Master of Science

La présence de buée sur des surfaces transparentes altère la transmission de la lumière. La buée est un ensemble de gouttes condensées sur une surface froide. Ces gouttes absorbent, réfléchissent et diffractent la lumière, réduisant la transparence de la surface sur laquelle elles se sont formées. Ce phénomène peut, en fonction des applications, causer des problèmes esthétiques et de sécurité. Une solution répandue dans le secteur industriel est l’utilisation de revêtements chimiques. Mais cette approche à un coût ; elle oblige à ajouter une nouvelle étape sur la chaine de production. Une autre solution, celle choisie durant ce doctorat, est l’approche topographique. En contrôlant la topographie par texturation de surface, les propriétés de mouillage peuvent être pilotées. Ainsi, des surfaces antibuées peuvent être développées. En fonction de la surface initiale, deux mécanismes sont possibles. Sur des surfaces hydrophiles, la création d’un film liquide uniforme remplaçant les gouttes d’eau est à privilégier. Avec ce type de film, la surface conserve de bonnes propriétés de transparence. Si la surface est plutôt hydrophobe, l’idée est de favoriser le déperlement des gouttes et ainsi d’évacuer l’eau le plus rapidement possible. Les travaux de ce doctorat portent sur le développement d’un traitement de surface topographique par injection plastique. Ce traitement vise à supprimer l’impact optique de la buée sur les surfaces en polycarbonate transparent des phares automobiles. L’une des contraintes majeures de ces travaux est de concevoir des texturations de surfaces facilement industrialisables. Les moyens de texturations doivent être adaptés. / The presence of dew on transparent pieces impairs light transmission. Dew is a group of droplets condensed on cold surfaces. These droplets absorb, reflect and diffract light, reducing condensation surface transparency. This can cause aesthetic or security issues. The most widely used method currently for improving transparency of surfaces covered with dew is to apply anti-fog chemical coatings. These coatings suppress the whitish opaque layer caused by condensation by reducing the surface tension of water droplets, causing them to disperse into a thin liquid sheet. However, this solution is expensive. It is adding a step in the production line. Surface texturing offers a viable alternative to the use of chemicals. Controlling the surface topography by modifying textured allows wetting property management. This approach, chosen during this PhD thesis, allows the design of anti-fog surfaces. Depending on the surface, two droplets suppression mechanisms are possible. On hydrophilic surfaces, liquid sheet formation replacing droplets has to be favored. If the surface is hydrophobic, droplets sliding off should be increased, thus water evacuation will be faster. Our work consists in the development of a topographical surface treatment by molding injection. The aim is to limit the optical impact of the dew on transparent polycarbonate surfaces of car headlights. The major constraint of this work is to design easy industrialized textured surfaces. Production means must be adapted.

Le polycarbonate (PC) est un matériau polymère très répandu, fort apprécié pour sa faible densité, sa transparence, ses bonnes propriétés mécaniques et surtout pour son faible coût. Même s’il présente quelques limites essentiellement liées à sa faible résistance à l’abrasion, à la rayure et à sa dégradation dans le temps (sous UV ou hydrolyse), le PC trouve sa place dans un large spectre d’applications (bâtiment, automobile, médical, optique…). Il reste à ce jour indispensable sur ce marché car aucun autre polymère ne présente d’aussi bonnes propriétés mécaniques à prix égal. C’est dans ce contexte que ces travaux de thèse ont permis de développer une solution permettant de protéger le PC de toute agression extérieure par le dépôt d’un revêtement protecteur. L’étude s’est orientée vers le dépôt d’un film hydride organique / inorganique à base de silice, préparé par voie sol-gel, ce procédé permettant une élaboration à une température compatible avec la température de transition vitreuse du PC (Tg) (148°C). Les solutions retenues pour obtenir un revêtement performant sont basées sur la synthèse de revêtements hybrides à base d’oxydes de silicium et de zirconium. Une attention particulière a été portée sur l’augmentation de l’adhérence du film au substrat d’une part, et l’optimisation du procédé (synthèse et traitement de densification), d’autre part. Les résultats sont présentés d’un point de vue physico-chimique (IR, XRR, RMN) et mécanique (nanoindentation, adhésion et test à la rayure). / The polycarbonate is a widespread polymer material, highly appreciated for its low density, its transparency and its good mechanical properties. This material is used for divert applications (automotive, medical, optical...) and is very competitive in terms of quality and prices. However, it displays some weaknesses, essentially due to its poor abrasion and scratch resistance and its possible degradation under UV or hydrolysis. In this context, the PhD aim is to design and develop a new hybrid organic / inorganic protective coating with silica and zirconia based precursors prepared by the sol gel process, which allow a curing compatible with the polycarbonate's Tg (148°C). Here, it is discussed on the solutions retained to obtain a scratch resistant, hydrophobic and transparent coating. It is showed that, scratch resistant protective coatings can be deposited on pristine PC thanks to a performing hybrid organic / inorganic coating by modulating its bulk properties. Moreover, results demonstrate the key role played by a phenylsilane precursor in enhancing the adherence. Nanoindentation, scratch-test, NMR and FTIR analysis will be discussed.

Les polyesters et polycarbonates aliphatiques biocompatibles et biodégradables sont typiquement utilisés pour la fabrication de matériaux médicaux tels que les fils de sutures ou les capsules de libération contrôlée de principe actif. Ces polymères synthétiques sont aussi développés comme substituts aux plastiques issus du pétrole. La méthode de choix pour obtenir des polycarbonates ou polyesters de longueur et de structure contrôlée est la polymérisation par ouverture de cycle (ROP) de monomères cycliques à cinq ou six chaînons. Actuellement, la majorité de ces polymères présentent des propriétés physiques intéressantes mais souvent limitées à certaines applications spécifiques. Des efforts sont donc consacrés à la synthèse de nouveaux monomères et polymères ou copolymères avec des microstructures contrôlées afin de moduler à convenance les propriétés thermiques et mécaniques du matériau final. Tandis que le poly(triméthylène carbonate), PTMC, est un élastomère, le poly(L-lactide), PLLA, est un polyester fragile. L’association de ces monomères au sein d’un copolymère a permis d’améliorer et de moduler les propriétés thermo-mécaniques du PLLA. Selon la nature de la copolymérisation (séquentielle ou simultanée) et du système catalytique utilisé, des copolymères de microstructures différentes ont été obtenus. Cette approche a permis de synthétiser de nouveaux polycarbonates ou poly(carbonate-co-ester) bien définis, notamment à partir de carbonates cycliques à cinq chaînons, comme le carbonate d’éthylène ou le carbonate de cyclohexène, réputés non polymérisable. Il devient alors envisageable de préparer de nouveaux polymères jusqu’alors supposés non synthétisable et ainsi d’accéder à de nouveaux matériaux biodégradable susceptibles de pouvoir remplacer les polymères de commodités problématiques comme le polycarbonate de bisphénol A. / Biocompatible and biodegradable aliphatic polyesters and polycarbonates are typically used for the manufacture of medical devices such as sutures or capsules for controlled release of active molecules. These synthetic polymers are also developed as substitutes for petroleum-based plastics. The method of choice for the synthesis of polycarbonates or polyesters with controlled length and structure is the ring-opening polymerization (ROP) of five or six membered ring cyclic monomers. Currently, the majority of these polymers exhibit interesting physical properties but often limited to specific applications. Efforts are therefore devoted to the synthesis of new monomers and polymers or copolymers with controlled microstructure to modulate at convenience the thermal and mechanical properties of the final material. Whereas poly(trimethylene carbonate), PTMC, is an elastomer, poly(L-lactide), PLLA, is a fragile polyester. The combination of these monomers in a copolymer has improved and modulate the thermo-mechanical properties of PLLA. Depending on the nature of the copolymerization (sequential or simultaneous) and the catalytic system used, copolymers of different microstructures were obtained. This approach has allowed to synthesize new well defined polycarbonates or poly(carbonate-co-ester), especially from five-membered cyclic carbonates such as ethylene carbonate or cyclohexene carbonate, known for being not polymerizable. It then becomes possible to prepare new polymers supposed to be not synthesizable and access to new biodegradable materials that can replace problematic commodity polymers such as bisphenol A polycarbonate.

Nesta tese procuramos caracterizar o Policarbonato Bisfenol-A, Durolon&#174 sob o ponto de vista elétrico, separando a reação dipolar e os processos de condução. Apesar de preparadas de forma análoga, as amostras (&#8773 30&#956m de espessura) mostraram comportamento pouco reprodutível, principalmente da componente condutiva. Várias anomalias foram detectadas embora não estudadas em detalhe pela pobre reprodutibilidade já mencionada. Além das técnicas usuais de polarização e despolarização isotérmicas, despolarização termoestimulada e de polarização termoestimulada, empregou-se pela primeira vez, em medidas desta natureza, a técnica de oscilação senoidal da temperatura, estando o campo elétrico aplicado. Media-se a corrente daí decorrente, procurando-se trabalhar sempre com uma mesma amostra. Na região de 50&#176C a 70&#176C, diferenças de fase superiores a 90&#176 foram encontradas (o sinal de corrente atrasado em relação ao de temperatura). Uma análise simples destes resultados indica que, neste caso, tanto a condutividade como a suscetibilidade diminuem com o crescimento da temperatura (dX/dT&#8773 -1x10-3/&#176C). Medidas de polarização termoestimulada, também, mostram uma inversão da corrente em relação ao campo aplicado desde cerca da temperatura ambiente ate &#8773 90&#176C. Um estudo sistemático da condução a 120&#176C indica que portadores são emitidos do eletródio, e que o trânsito dos mesmos é rápido (menor do que o tempo em que a polarização se estabelece, &#8773 2 min). Tensões e correntes espontâneas foram detectadas mesmo em amostras providas de eletródios de mesmo metal (uma correlação com a ordem empregada na metalização foi suspeitada, seguindo observação anteriormente feita pelo Prof. B. Gross). Algumas medidas com eletródios Al-Al, Al-Au e Au-Au foram feitas. Finalmente, sugestões para trabalhos futuros são feitas. / In this work the electrical characterization of the Polycarbonate Bisphenol-A, Durolon &#174 was attempted, trying to separate the dipole and the conduction processes. However, poor reproducibility, mainly in the conductivity, was achieved even for samples (&#8773 30&#956m thick usually) taken from the same batch. Anomalies were detected but not studied in detail owing the poor reproducibility referred above. Beside the usual techniques like the isothermal polarization and depolarization in short-circuit, thermally depolarization currents and thermally stimulated polarization, in a new one, employed by the first time for the study of transport and polarization, the temperature was oscillated and the ensuing current oscillation was monitored. Large phase shifts (the current lagging the temperature oscillation), even greater &#8773 90&#176 were found in the range 50&#176C 70&#176C. A simple analysis indicates that in this case both the conductivity as well as the susceptibility are decreased for increasing temperature (dX/dT&#8773 -1x10-3/&#176C). Accordingly thermally stimulated polarization shows a current reversal with respect to the electric field from room temperature to &#8773 90&#176C. A systematic study of the conduction process at 120&#176C was carried out, the analysis of which indicates that carriers are emitted from the electrode, whose transit across the sample is shorter than the duration of the polarization current (&#8773 2 min). Spontaneous tensions and currents were detected even for samples provisioned with similar electrodes (a correlation with the actual sequence of metallization, following a suggestion by Prof. B. Gross, was surmised). A few measurements with Al-Al, Al-Au and Au-Au electrodes were carried out. Finally suggestions for future work are given.

This dissertation is written in two parts. The first pertains to polycarbonate and polyester synthesis using relatively benign processes. The synthesis of polycarbonates from the coupling of CO2 and epoxides catalyzed by transition metal catalysts has long been studied in the DJD group. The benefits of this process are that it utilizes comparatively benign reagents, can be performed using no extraneous solvent, and is 100% atom efficient. A method potentially useful for achieving more desirable polycarbonate properties is to produce an epoxide A/epoxide B/CO2 terpolymer, thus allowing more fine "tuning" of properties to what one may desire while simultaneously influencing relative epoxide reactivity to potentially increase catalytic turnovers. Specifically, the coupling of propylene oxide and cyclohexene oxide with CO2 to yield a random copolymer with tunable properties has been studied via a Fineman-Ross analysis. Propylene oxide was found to be incorporated into the resultant polymer chain with anywhere from 4-10 times the preference of cylcohexene oxide. Although it has been reported as early as 1969, the copolymerization of epoxides and cyclic anhydrides catalyzed by transition metal complexes to yield polyesters via a chain-growth mechanism has recently gained much attention. This robust method of polyester synthesis can utilize rather inexpensive reagents to synthesize an array of polyester products which have a wide range of Tg values (-30 degrees C ? 90 degreesC), achievable through simple monomer selection. The second part of this dissertation deals with the kinetic study of ligand substitution from manganese carbonyl metal fragments. Some time ago it was postulated that complexes of the (Cp)M(CO)2L variety undergo ligand substitution via a associative mechanism allowed by a haptotropic eta5-eta3 shift in the eta5 ligand. Through kinetic studies and theoretical modeling, an approximate activation energy barrier of ~34 kJ/mol has been calculated for the ring slip of (2,5-dimethylpyrrole)Mn to occur. Additionally, further kinetic studies were performed in which Tp, a ligand electronically similar to Cp, was compared to MnCp complexes.

In this study, the effect of compatibilizers on the gas separation performance of polycarbonate (PC) membranes was investigated. Membranes were prepared by solvent evaporation method. They were characterized by single gas permeability measurements of O2, N2, H2 and CO2 as well as scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and Fourier transform infrared spectrometry (FTIR). Membranes containing 0.5 to 10 w% p-nitroaniline (pNA) were prepared to study the effect of compatibilizer concentration on the membrane performance. Permeabilities of all gases decreased but selectivities increased with pNA concentration. The membranes with 5 w% pNA showed a selectivity of 114.5 for H2 over N2, 53.9 for CO2 over N2 and 13.4 for O2 over N2 at room temperature, whereas, the H2/N2, CO2/N2 and O2/N2 selectivities for pure PC membranes were 43.5, 20.6 and 5.6, respectively. The N2 permeabilities through pure PC membrane and 5 w% pNA/PC membrane were 0.265 and 0.064 barrer, respectively. The glass transition temperature of the membranes decreased with increasing pNA concentration. FTIR spectra showed that the peaks assigned to nitro and amine groups of pNA shifted and/or broadened. The DSC and FTIR results suggested an interaction between PC and pNA. The effect of type of compatibilizer was also studied. The compatibilizers were 4-amino 3-nitro phenol (ANP), Catechol and 2-hydroxy 5-methyl aniline (HMA). Similar to membranes prepared with pNA, membranes prepared with these compatibilizers had a lower permeability and glass transition temperature but higher selectivity than pure PC membranes. Their FTIR spectra were also indicated a possible interaction between PC and compatibilizer. In conclusion, PC/compatibilizer blend membranes for successful gas separation were prepared. Low molecular weight compounds with multifunctional groups were found to effect membrane properties at low concentration range, 0.5-5 w%.

<p>An advanced bulk constitutive model is used with a new cohesive zone model that is stress state and rate-dependent in order to simulate the ductile to brittle failure transition in polycarbonate. The cohesive zone model is motivated by experimental evidence that two different critical energies per unit area of crack growth exist in glassy polymers. A higher energy state is associated with ductile failure (slow crack growth), while a lower energy state is associated with brittle failure (fast crack growth). The model is formulated so that as rate or stress state changes within a simulation, the fracture energy and thus fracture mode may also change appropriately. The ductile to brittle transition occurs when the cohesive opening rate is over a threshold opening rate and when the stress state is close to plane strain in a fracture specimen. These effects are coupled. The principal contribution of this work is that this is the first time a single set of material input parameters can predict the transition from slow to fast crack growth as test loading rate and sample thickness are varied. This result enlisted the use of an advanced constitutive model and the new cohesive zone model with rate and stress-state dependencies in three-dimensional finite element analysis.</p> / Dissertation