Materiais poliméricos são amplamente utilizados e, atualmente, especificações mais rígidas para aplicações especiais tem sido impostas a esses materiais. A microestrutura, em geral, exerce intensa influência na determinação das propriedades macroscópicas dos materiais, sendo assim, o controle da microestrutura e seu relacionamento com essas propriedades é de interesse estratégico. Modelos matemáticos dos processos de polimerização são importantes para relacionar as variáveis de processo com a produtividade e a microestrutura do polímero. Neste trabalho um modelo matemático do processo de copolimerização em emulsão do acrilato de butila com o acetato de vinila foi elaborado. O modelo matemático gerado constitui-se num sistema que engloba equações algébricas (p.ex., de equilíbrio de fases) e diferenciais ordinárias de primeira ordem (p.ex., os balanços de massa dos componentes), num conjunto algébrico diferencial não linear de primeira ordem (DAE). Esse sistema foi solucionado numericamente utilizando-se, tanto o método BDF (backward differentiation formulas) quanto as NDF (numerical differentiation formulas), implementado em MATLAB 6.5R13; mais especificamente, obtiveram-se bons resultados utilizando-se a ode113. Os resultados mostram que o modelo representa razoavelmente bem os dados experimentais de trabalhos anteriores do grupo de pesquisa, embora um dos três parâmetros de identificação do modelo tenha sido penalizado com valores abaixo daqueles geralmente reportados na literatura. Apesar disso, o modelo mostrou-se funcional e pode ser útil na simulação do processo. Perfis polinomiais de variações temporais de temperatura também foram aplicados na etapa de otimização simples dos parâmetros das equações desses perfis, objetivando melhorias (redução) no tempo de reação. Observou-se, todavia, que o sistema DAE é de implementação complicada e requer cuidados adicionais na etapa de geração da inicialização consistente e de atribuição dos valores iniciais dos parâmetros do modelo, assim como tende a manifestar complicações na etapa de identificação do modelo. / Polimeric materials have been largely used and, today, more stringent specifications have been imposed to these materials for special applications. In general, microstructure exercises intense influence on the macroscopic properties of the polymer: therefore, the control of the microstructure and its relation with these properties is of strategic interest. Mathematical models of the polymerization processes are important tools to predict the effect of process variables with the process productivity and the polymer microstructure. In this work a mathematical model of the emulsion copolymerization process of butyl acrylate and vinyl acetate was elaborated. The resulting model is a system of DAE (differential algebraic equations) and was solved numerically using the function ode113 of the software MATLAB6.5R13, employing both BDF (backward differentiation formulas) and NDF (numerical differentiation formulas) methods. The results show that the model is able to represent reasonably well the experimental data taken from previous works of the research group, although one of the three identification parameters had been adjusted to values lower than those reported in the literature. Nevertheless, the model is functional and can be useful for process simulation. Polynomial curves of temperature versus time variations were also studied for optimizing the polynomial coefficients, seeking the improvement (reduction) of the reaction time. However, it was observed that DAE implementation is complicated and demands further careful procedures for generating consistent initialization conditions for attributing good initial values for the model parameters, presenting difficulties in the model identification step.

A multidisciplinary literature survey revealed that copolymeric nanoparticles could be applied in various technologies such as the production of paint, adhesives, packaging material and lately especially drug delivery systems. The specialized application and investigation of copolymers in drug delivery resulted in the synthesis of two series of copolymeric materials, i.e. poly(styrene-co-methyl methacrylate) (P(St-co-MMA)) and poly(styrene-co-ethyl methacrylate) (P(St-co-EMA)) were synthesized via the technique of o/w microemulsion copolymerization. These copolymers have not as yet been utilized to their full potential in the development of new drug delivery systems. However the corresponding hydrophobic homopolymer poly(styrene) (PS) and the hydrophilic homopolymer poly(methyl methacrylate) (PMMA) are known to be biocompatible. Blending of homopolymers could result in novel applications, however is virtually impossible due to their unfavorable mixing entropies. The immiscibility challenge was overcome by the synthesis of copolymers that combined the properties of the immiscible homopolymers. The synthesized particles were analyzed by gel permeation chromatography combined with multi-angle laser light scattering (GPC-MALLS) and attenuated total reflectance Fourier infrared spectroscopy (ATR-FTIR). These characterizations revealed crucial information to better understand the synthesis process and particle properties i.e. molecular weight, nanoparticle size and chemical composition of the materials. Additionally, GPC-MALLS revealed the copolymer chain conformation. These characterizations ultimately guided the selection of appropriate copolymer nanoparticles to develop a controlled-release drug delivery system. The selected copolymers were dissolved in a pharmaceutically acceptable solvent, tetrahydrofuran (THF) together with a drug, rifampin. Solvent casting of this dispersion resulted in the evaporation of the solvent and assembly of numerous microscale copolymer capsules. The rifampin molecules were captured in these microcapsules through a process of phase separation and coacervation. These microcapsules finally sintered to produce a multi-layer film with an unusual honeycomb structure, bridging yet another size scale hierarchy. Characterization of these delivery systems revealed that both series of copolymer materials produced films capable of controlling drug release and that could also potentially prevent biofilm adhesion. / Thesis (Ph.D. (Pharmaceutics))--North-West University, Potchefstroom Campus, 2008.

In recent years there have been many efforts to develop and expand the ability of mathematical models capable of describing polymerization systems. Models can provide a key competitive advantage for the industry and research in terms of production and technology development. As new resins are continuously produced to meet the requirement of final applications and processability, it is imperative to pursue strong polymer characterization with special attention to detailed analysis of polymer microstructure. The microstructure of polyolefin is defined by its distribution of molecular weight, chemical composition, branching topology, and stereoregularity. <br /><br /> In this work, a Monte Carlo simulation model was developed to describe the polymerization mechanisms of olefin homopolymerization and copolymerization using single-site coordination catalyst. The mathematical model is meant to describe molecular weight and chemical composition distribution in copolymerization system. More specifically, this research work gives a detailed study of the molecular structure for ethylene- alfa-olefin copolymer. <br /><br /> The chemical and physical properties of copolymers are influenced not only by their average composition, but also by the monomer sequence distribution along the polymer chains. Predicting the molecular weight and comonomer distributions can lead to a better understanding of the possible morphology in solid stated because they are considered to be the main structural parameters that affect the crystallinity of polymeric materials. As a consequence, final physical properties such as the tensile properties of a copolymer could be controlled by the ratio of crystalline species in the polymer. <br /><br /> This work is considered to be a useful tool that enables us to understand and explore specific polymerization catalytic system. Being able to describe the short chain branching and the monomer sequence distribution as a function of chain length enables us to have a better control over semi-batch polymerization reactors.

In recent years there have been many efforts to develop and expand the ability of mathematical models capable of describing polymerization systems. Models can provide a key competitive advantage for the industry and research in terms of production and technology development. As new resins are continuously produced to meet the requirement of final applications and processability, it is imperative to pursue strong polymer characterization with special attention to detailed analysis of polymer microstructure. The microstructure of polyolefin is defined by its distribution of molecular weight, chemical composition, branching topology, and stereoregularity. <br /><br /> In this work, a Monte Carlo simulation model was developed to describe the polymerization mechanisms of olefin homopolymerization and copolymerization using single-site coordination catalyst. The mathematical model is meant to describe molecular weight and chemical composition distribution in copolymerization system. More specifically, this research work gives a detailed study of the molecular structure for ethylene- alfa-olefin copolymer. <br /><br /> The chemical and physical properties of copolymers are influenced not only by their average composition, but also by the monomer sequence distribution along the polymer chains. Predicting the molecular weight and comonomer distributions can lead to a better understanding of the possible morphology in solid stated because they are considered to be the main structural parameters that affect the crystallinity of polymeric materials. As a consequence, final physical properties such as the tensile properties of a copolymer could be controlled by the ratio of crystalline species in the polymer. <br /><br /> This work is considered to be a useful tool that enables us to understand and explore specific polymerization catalytic system. Being able to describe the short chain branching and the monomer sequence distribution as a function of chain length enables us to have a better control over semi-batch polymerization reactors.

Biodegradable aliphatic polycarbonates are important components of non-toxic thermoplastic elastomers, which have a variety of medical applications. Industrially, aliphatic polycarbonates derived from six-membered cyclic carbonates such as trimethylene carbonate (TMC or 1,3-dioxan-2-one) are produced via ring-opening polymerization (ROP) processes in the presence of a tin catalyst. It is worth mentioning that TMC is readily obtained by transesterification of 1,3-propanediol with various reagents including phosgene and its derivatives. Therefore, it has been of great interest to investigate greener routes for the production of this important class of polymers. Toward this goal, the synthesis of aliphatic polycarbonates via the metal catalyzed alternative coupling of oxetanes and carbon dioxide represents an attractive alternative. The use of an abundant, inexpensive, non-toxic, and biorenewable resource, carbon dioxide, makes this method very valuable. Furthermore, in this reaction, the sixmembered cyclic carbonate byproduct, TMC, can also be ring-opened and transformed into the same polycarbonate. For over a decade, the Darensbourg research group has successfully utilized metal salen complexes as catalysts for the epoxide/CO2 copolymerization process. Hence, this dissertation focuses on the examination of these complexes as catalysts for the oxetane/CO2 copolymerization reaction and the further elucidation of its mechanism. Chromium(III) salen derivatives in the presence of an azide ion initiator were determined to be very effective catalysts for the coupling of oxetanes and carbon dioxide providing polycarbonates with minimal amounts of ether linkages. Kinetic and mechanistic investigations performed on this process suggested that copolymer formation proceeded by two routes. These are the direct enchainment of oxetane and CO2, and the intermediacy of trimethylene carbonate, which was observed as a minor product of the coupling reaction. Anion initiators which are good leaving groups, e.g. bromide and iodide, are effective at affording TMC, and hence, more polycarbonate can be formed by the ROP of preformed trimethylene carbonate. Research efforts at tuning the selectivity of the oxetane/CO2 coupling process for TMC and/or polycarbonate produced from the homopolymerization of preformed TMC have been performed using cobalt(II) salen derivatives along with anion initiators. Lastly, investigations of this process involving 3-methoxy-methyl-3-methyloxetane will be presented.

Polycarbonates are found in a variety of common products in daily life due to their favorable mechanical and electrical properties. In addition, they are widely used in biomedical areas due to their stability and biological inertness. Therefore, the production of polycarbonates became an important industrial process in the past decades. However, the current industrial process usually requires toxic phosgene gas as a starting material. Thus, the environmentally benign route by using metal catalyzed couplings of epoxides and CO_(2) to produce polycarbonates has received attention from researchers. In this dissertation, metal catalyzed CO_(2)/cyclic ether copolymerization, depolymerization of polycarbonates, and the equilibria between polycarbonate and corresponding six-membered cyclic carbonate will be investigated. First, the Co(III) catalyzed copolymerizations of CO_(2) and various epoxides with electron-withdrawing substituents to afford polycarbonates are examined. Comparative kinetic studies were performed via in situ infrared measurements as a function of temperature to assess the activation barriers for the production of cyclic carbonate versus copolymer involving electronically different epoxides: styrene oxide, epichlorohydrin, and propylene oxide. Thermodynamically stable cyclic carbonate byproducts are produced during the course of the reaction from the degradations of propagating polymer chains. The depolymerization reactions of several polycarbonates produced from the completely alternating copolymerization of styrene oxide, epichlorohydrin, propylene oxide, cyclohexene oxide, indene oxide, and cyclopentene oxide with carbon dioxide have been investigated. Various reaction pathways can be found under different reaction conditions, including process involving chain-end backbiting and radical intermediates. Temperature-dependent kinetic studies have provided energy of activation barriers for cyclic carbonate formation. In addition, the generated monomeric materials from the degradation of select polycarbonates show the possibility of chemical recycling of plastic waste. For the copolymers made from CO_(2) and oxetane derivatives, this study focuses on the influence of steric hindrance in the 3-position of the monomer oxetane. The (salen)CrCl/onium salt catalyzed coupling reactions of these oxetane derivatives and carbon dioxide are reported. Depolymerizations of copolymers to their corresponding cyclic carbonates were also studied. In addition, several six-membered cyclic carbonates were synthesized to examine their equilibria between monomeric cyclic carbonates and their corresponding polycarbonates.

The purpose of this research was to synthesize the constrained geometry catalyst Ti[(C5Me4)SiMe2(tBuN)]Cl2 (1) with MAO as a cocatalyst for ethylene homopolymerization and copolymerizations with 1-TMSO-alkenes to produce a copolymer with polar functionality. Three 1-alkenols of varying length were purchased and derivatized and used for the copolymerization experiments: 2-propen-1-ol, 3-buten-1-ol and 9-decen-1-ol. Several variables were tested to determine their effects on comonomer incorporation such as temperature, equivalents of comonomer, equivalents of MAO and two different solvents. Higher catalytic activities were correlated with fewer equivalents of polar comonomer, lower temperatures, and no fewer than 1000 equivalents of MAO. Toluene was found to be a far more effective reaction solvent than dichloromethane, as polymer yields were on average thirteen times higher. All polymer samples were analyzed by high temperature 1H NMR spectroscopy and selected samples were analyzed by DSC and IR spectroscopy. DSC determined that the polyethylene produced by 1 was substantially linear HDPE with long chain branching and that comonomer incorporation reduced the Tc and Tm, probably due to increased short chain branching. 1-TMSO-9-Decene was the most effective comonomer, as it had the highest incorporation rates (8.0 mol%) of all three of the polar comonomers. The two shorter comonomers exhibited no incorporation at all. This confirmed the hypothesis that polar comonomers with longer chains would be less prone to poisoning the electrophilic catalyst. / Thesis (Master, Chemistry) -- Queen's University, 2009-04-27 10:16:46.356

A multidisciplinary literature survey revealed that copolymeric nanoparticles could be applied in various technologies such as the production of paint, adhesives, packaging material and lately especially drug delivery systems. The specialized application and investigation of copolymers in drug delivery resulted in the synthesis of two series of copolymeric materials, i.e. poly(styrene-co-methyl methacrylate) (P(St-co-MMA)) and poly(styrene-co-ethyl methacrylate) (P(St-co-EMA)) were synthesized via the technique of o/w microemulsion copolymerization. These copolymers have not as yet been utilized to their full potential in the development of new drug delivery systems. However the corresponding hydrophobic homopolymer poly(styrene) (PS) and the hydrophilic homopolymer poly(methyl methacrylate) (PMMA) are known to be biocompatible. Blending of homopolymers could result in novel applications, however is virtually impossible due to their unfavorable mixing entropies. The immiscibility challenge was overcome by the synthesis of copolymers that combined the properties of the immiscible homopolymers. The synthesized particles were analyzed by gel permeation chromatography combined with multi-angle laser light scattering (GPC-MALLS) and attenuated total reflectance Fourier infrared spectroscopy (ATR-FTIR). These characterizations revealed crucial information to better understand the synthesis process and particle properties i.e. molecular weight, nanoparticle size and chemical composition of the materials. Additionally, GPC-MALLS revealed the copolymer chain conformation. These characterizations ultimately guided the selection of appropriate copolymer nanoparticles to develop a controlled-release drug delivery system. The selected copolymers were dissolved in a pharmaceutically acceptable solvent, tetrahydrofuran (THF) together with a drug, rifampin. Solvent casting of this dispersion resulted in the evaporation of the solvent and assembly of numerous microscale copolymer capsules. The rifampin molecules were captured in these microcapsules through a process of phase separation and coacervation. These microcapsules finally sintered to produce a multi-layer film with an unusual honeycomb structure, bridging yet another size scale hierarchy. Characterization of these delivery systems revealed that both series of copolymer materials produced films capable of controlling drug release and that could also potentially prevent biofilm adhesion. / Thesis (Ph.D. (Pharmaceutics))--North-West University, Potchefstroom Campus, 2008.

A multidisciplinary literature survey revealed that copolymeric nanoparticles could be applied in various technologies such as the production of paint, adhesives, packaging material and lately especially drug delivery systems. The specialized application and investigation of copolymers in drug delivery resulted in the synthesis of two series of copolymeric materials, i.e. poly(styrene-co-methyl methacrylate) (P(St-co-MMA)) and poly(styrene-co-ethyl methacrylate) (P(St-co-EMA)) were synthesized via the technique of o/w microemulsion copolymerization. These copolymers have not as yet been utilized to their full potential in the development of new drug delivery systems. However the corresponding hydrophobic homopolymer poly(styrene) (PS) and the hydrophilic homopolymer poly(methyl methacrylate) (PMMA) are known to be biocompatible. Blending of homopolymers could result in novel applications, however is virtually impossible due to their unfavorable mixing entropies. The immiscibility challenge was overcome by the synthesis of copolymers that combined the properties of the immiscible homopolymers. The synthesized particles were analyzed by gel permeation chromatography combined with multi-angle laser light scattering (GPC-MALLS) and attenuated total reflectance Fourier infrared spectroscopy (ATR-FTIR). These characterizations revealed crucial information to better understand the synthesis process and particle properties i.e. molecular weight, nanoparticle size and chemical composition of the materials. Additionally, GPC-MALLS revealed the copolymer chain conformation. These characterizations ultimately guided the selection of appropriate copolymer nanoparticles to develop a controlled-release drug delivery system. The selected copolymers were dissolved in a pharmaceutically acceptable solvent, tetrahydrofuran (THF) together with a drug, rifampin. Solvent casting of this dispersion resulted in the evaporation of the solvent and assembly of numerous microscale copolymer capsules. The rifampin molecules were captured in these microcapsules through a process of phase separation and coacervation. These microcapsules finally sintered to produce a multi-layer film with an unusual honeycomb structure, bridging yet another size scale hierarchy. Characterization of these delivery systems revealed that both series of copolymer materials produced films capable of controlling drug release and that could also potentially prevent biofilm adhesion. / Thesis (Ph.D. (Pharmaceutics))--North-West University, Potchefstroom Campus, 2008.

Materiais poliméricos são amplamente utilizados e, atualmente, especificações mais rígidas para aplicações especiais tem sido impostas a esses materiais. A microestrutura, em geral, exerce intensa influência na determinação das propriedades macroscópicas dos materiais, sendo assim, o controle da microestrutura e seu relacionamento com essas propriedades é de interesse estratégico. Modelos matemáticos dos processos de polimerização são importantes para relacionar as variáveis de processo com a produtividade e a microestrutura do polímero. Neste trabalho um modelo matemático do processo de copolimerização em emulsão do acrilato de butila com o acetato de vinila foi elaborado. O modelo matemático gerado constitui-se num sistema que engloba equações algébricas (p.ex., de equilíbrio de fases) e diferenciais ordinárias de primeira ordem (p.ex., os balanços de massa dos componentes), num conjunto algébrico diferencial não linear de primeira ordem (DAE). Esse sistema foi solucionado numericamente utilizando-se, tanto o método BDF (backward differentiation formulas) quanto as NDF (numerical differentiation formulas), implementado em MATLAB 6.5R13; mais especificamente, obtiveram-se bons resultados utilizando-se a ode113. Os resultados mostram que o modelo representa razoavelmente bem os dados experimentais de trabalhos anteriores do grupo de pesquisa, embora um dos três parâmetros de identificação do modelo tenha sido penalizado com valores abaixo daqueles geralmente reportados na literatura. Apesar disso, o modelo mostrou-se funcional e pode ser útil na simulação do processo. Perfis polinomiais de variações temporais de temperatura também foram aplicados na etapa de otimização simples dos parâmetros das equações desses perfis, objetivando melhorias (redução) no tempo de reação. Observou-se, todavia, que o sistema DAE é de implementação complicada e requer cuidados adicionais na etapa de geração da inicialização consistente e de atribuição dos valores iniciais dos parâmetros do modelo, assim como tende a manifestar complicações na etapa de identificação do modelo. / Polimeric materials have been largely used and, today, more stringent specifications have been imposed to these materials for special applications. In general, microstructure exercises intense influence on the macroscopic properties of the polymer: therefore, the control of the microstructure and its relation with these properties is of strategic interest. Mathematical models of the polymerization processes are important tools to predict the effect of process variables with the process productivity and the polymer microstructure. In this work a mathematical model of the emulsion copolymerization process of butyl acrylate and vinyl acetate was elaborated. The resulting model is a system of DAE (differential algebraic equations) and was solved numerically using the function ode113 of the software MATLAB6.5R13, employing both BDF (backward differentiation formulas) and NDF (numerical differentiation formulas) methods. The results show that the model is able to represent reasonably well the experimental data taken from previous works of the research group, although one of the three identification parameters had been adjusted to values lower than those reported in the literature. Nevertheless, the model is functional and can be useful for process simulation. Polynomial curves of temperature versus time variations were also studied for optimizing the polynomial coefficients, seeking the improvement (reduction) of the reaction time. However, it was observed that DAE implementation is complicated and demands further careful procedures for generating consistent initialization conditions for attributing good initial values for the model parameters, presenting difficulties in the model identification step.