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.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This work presents the development and validation of analytical methods to assay daptomycin injection. Daptomycin is a drug of a new class of antibiotics, known as cyclic lipopeptides. It was approved in USA in 2003 and in Brazil in 2009. Up to now, there are no reports about methods to assay the drug in pharmaceutical products, both in scientific literature or in official compendia. Methods to identify daptomycin in raw material were realized as solubility, melting point, infrared spectrophotometry (IR), ultraviolet spectrophotometry (UV) and differential scanning calorimetry (DSC) and they showed appropriate results. The following methods to assay daptomycin injection were developed and validated: high performance liquid chromatography (HPLC), microbiological assay (turbidimetric) and UV-spectrophotometry. All of them were validated according current guidelines, by the following parameters: specificity, linearity, precision, accuracy and robustness, being all the requirements met. The mean values of daptomycin assay by the three methods were: 100,23 ± 0,59% (HPLC); 100,96 ± 2,58% (turbidimetric assay) and 98,98 ± 1,35% (UV-spectrophotometry). They were compared by ANOVA, which indicated that HPLC and turbidimetric assay are interchangeable. The stress testing showed that daptomycin is very susceptible to alkaline medium and that the degradation follows first order kinetic, in the conditions adopted. It was found that the degradation product(s) of daptomycin do not have antimicrobial activity. Considering their characteristics, HPLC and turbidimetric assays can be used in routine quality control and in stability studies of daptomycin injection. / Este trabalho apresenta o desenvolvimento e validação de métodos analíticos para o doseamento da daptomicina injetável. A daptomicina é um antibiótico pertencente a uma nova classe de antimicrobianos, conhecidos como lipopeptídeos cíclicos. Foi aprovada para comercialização nos Estado Unidos em 2003 e no Brasil em 2009. Até o momento, não foram relatados métodos de quantificação para o fármaco em produtos farmacêuticos, tanto na literatura científica quanto em compêndios oficiais. Foram realizados métodos para a caracterização da matéria-prima como solubilidade, ponto de fusão, espectrofotometria no infravermelho (IV) e na região do ultravioleta (UV) e calorimetria exploratória diferencial (DSC), sendo que os mesmos permitiram a identificação do fármaco na matéria-prima. Os seguintes métodos para análise quantitativa da daptomicina injetável foram desenvolvidos e validados: cromatografia líquida de alta eficiência (CLAE), ensaio microbiológico (método turbidimétrico) e espectrofotometria na região do UV. Todos os métodos foram validados de acordo com as guias vigentes, frente aos parâmetros de especificidade, linearidade, precisão, exatidão e robustez, tendo sido atendidos os requisitos estabelecidos. Os teores médios de daptomicina na formulação em estudo, pelos métodos desenvolvidos (n=12/método) foram: 100,23 ± 0,59% (CLAE); 100,96 ± 2,58% (ensaio microbiológico) e 98,98 ± 1,35% (espectrofotometria no UV). Esses resultados foram comparados pelo teste de ANOVA, que indicou que os métodos de CLAE e microbiológico são intercambiáveis. Pelo estudo de degradação forçada verificou-se que a condição que induz à maior degradação do fármaco é o meio alcalino, sendo que a reação segue cinética de primeira ordem nas condições usadas. Constatou-se ainda que a amostra degradada da daptomicina não tem ação antimicrobiana. Pelas suas características, os métodos de CLAE e microbiológico podem sem usados no controle de qualidade de rotina e em estudos de estabilidade da formulação injetável de daptomicina.