No description available.

The miscibility of poly (methyl acrylate)/poly (vinyl acetate) (PMA/PVAc) and poly (vinyl acetate)/poly(vinylidene fluoride) (PVAc/PVF2) blends has been studied. Films of compositions 100/0, 80/20, 60/40, 50/50, 40/60, 20/80, and 0/100 (w/w) were cast for each system. Films of PMA/PVAc were found transparent and those of the PVAc/PVf2 were slightly opaque. While all the compositions of the PMA/PVAc exhibit single sharp Tgs, as measured with the differential scanning calorimeter, almost all of those of the PVAc/PVF2 exhibit s1 ng1 e broad TgS. By the single Tg criterion, the PVA/PVAc and PVAc/PVF2 systems are miscible in all proportions. Fourier transform infra-red spectroscopy spectra indicate molecular interaction complex involvement in the two systems. Evidence for such interaction was found to be significant in the 80% PMA/20% PVAc and 20% PVAc/80% PVF2 compositions.

No description available.

We have prepared a new class of polybenzoxazine based nanocomposites through DNA-like self-complementary multiple hydrogen bonding. At first, benzoxazine containing thymine (Bz-T), PEO containing adenine (PEO-A) group and POSS containing adenine (POSS-A) have been successfully synthesized, respectively. Those chemical structures were confirmed by 1H and 13C NMR and FT-IR spectroscopies. DSC and TGA analyses showed that the Bz-T had lower cross-link temperature and higher thermostability than benzoxazine containing methyl acrylate (BZ-ac) group. Moreover, TEM and WAXD provided a new evidence for linearly structure and self-assembly polybenzoxaine through self-complementary multiple hydrogen bonding of its T units. Then, PEO-A/PBz-T and POSS-A/PBz-T hybrid materials were prepared. SAX, WAXD, TEM and AFM analyses indicated that the size of PEO domain in PBz-T matrix was significantly decreased and the new type phase separation boundary (discrete domain through non-convent bonds) was obtained. Finally, we were using WAXD, TEM, DSC and nanoindenter to study properties of POSS-A/PBz-T nanocomposite. The presence of self-assembly nano-lamellate structure and enhance the mechanical properties on thin film, because of well-dispersion of POSS in PBz-T matrix through strong hydrogen bonding between A-T interactions.

Orientador: Maria Isabel Felisberti / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-12T11:50:16Z (GMT). No. of bitstreams: 1 Faria_ElaineCristina_M.pdf: 2819560 bytes, checksum: 35692ba489585c42469cd45337f16702 (MD5) Previous issue date: 2008 / Resumo: Neste trabalho, foram preparadas blendas de poli(cloreto de vinila), PVC, com elastômero termoplástico poli[estireno-g(etileno-co-propileno-co-dieno)-g-acrilonitrila), AES. O AES é uma mistura complexa de poli(estireno-co-acrilonitrila), SAN, poli(etileno-co-propileno-co-dieno), EPDM e do copolímero de enxertia EPDM-g-SAN. As blendas com 10, 20 e 30% de AES foram obtidas em extrusora dupla-rosca cônica. As blendas PVC/AES são heterogêneas, apresentando uma fina dispersão da fase EPDM na matriz da blenda. Análise dinâmico-mecânica e calorimetria diferencial de varredura mostraram fortes indícios de que há um certo grau de miscibilidade da fase SAN do AES e o PVC. Mais especificamente, foram observadas duas transições vítreas para as blendas; a da fase EPDM, deslocada para temperaturas menores em relação à fase EPDM do AES; a da matriz, deslocada para temperaturas intermediárias entre as transições do do PVC e do SAN. Esta miscibilidade entre a fase SAN do AES e o PVC, que resultou em uma boa adesão entre a fase PVC e a fase EPDM da blenda, levando a uma melhora significativa nas propriedades de resistência ao impacto e alongamento do PVC. As blendas de 10, 20 e 30% de AES apresentaram um aumento de 240, 460 e 160% respectivamente, no alongamento do PVC e as blendas de 20 e 30% de AES apresentaram respectivamente um aumento da resistência ao impacto de 2000 e 2700% se comparadas ao PVC original. / Abstract: Abstract: In this work blends of polyvinyl chloride, PVC and the thermoplastic elastomer poly[acrylonitrile-g-(ethylene-co-propylene-co-diene)-g-styrene] were prepared. AES is a complex mixture of poly[stiren-co-acrylonitrile), SAN, and poly (ethylen-co-propylene-co-diene), EPDM and the graft copolymer EPDM-g-SAN. These blends were prepared ina twin-screw conic extruder in the following compositions: 10, 20 and 30% wt of AES. The blends are heteroneneos, presenting a thin phase dispersion of EPDM in the matrix. Dinamic-mechanical analysis (DMA) and Differential Electronic Calorimitry (DSC) showed miscibility between PVC and SAN phase of AES. Two glass transitions were observed for blends: one related to EPDM phase, shifted to lower temperatures in comparison to EPDM in the neat AES and another to matrix, intermediate to PVC and SAN glass transition temperatures. The miscibility between SAN phase and PVC, which promotes a good adhesion between PVC and EPDM significantly improved the impact resistance and elongation. The blends of 10, 20 and 30% of AES present an increase in elongation values in 240, 460 and 160% respectively and the blends of 20 and 30% of AES present an improvement of impact resistance of 2000 and 2700% respectively comparing to the original PVC / Mestrado / Físico-Química / Mestre em Química

Abstract Synthetic routes were developed for the preparation of 2-alkoxy-4-hydroxybenzoic acids and 2-alkoxyhydroquinones, and a large-scale synthesis was developed for the preparation of 2-thioalkoxyhydroquinones. The 2-alkoxy-4-hydroxybenzoic acids, which contained alkyl side chains of different length, were used in the synthesis of new main chain liquid crystalline (LC) homo-, random, and block co-oligomers. In addition, oligomers of terephthaloyl chloride and 2-thioalkoxyhydroquinones and oligomers of terephthaloyl chloride and 2-alkoxyhydroquinones were produced. All the oligomers were blended with aliphatic polyamide 11 (PA 11). The effect of alkyl side chain length on the compatibility behavior of the LC oligomers towards the aliphatic polymer was characterized by DSC and FTIR, and the effect of side chain length on the flexural properties of the blends was investigated with a three-point bending test. The miscibility studies showed variable interfacial adhesion between the blended compounds. The strongest adhesion was achieved between PA 11 and the homo-oligomers of 2-alkoxy-4-hydroxybenzoic acids with short or medium long substituents (C4-C10), but the interactions between PA 11 and the oligomer with long aliphatic side chain (C18) were poor, as were those between PA 11 and the wholly aromatic oligomer of 4-hydroxybenzoic acid. The compatibility between PA 11 and the co-oligomers of 2-alkoxy-4-hydroxybenzoic acids was slightly lower than the compatibility of the corresponding homo-oligomers. DSC and FTIR analyses of the blends of oligomers of terephthaloyl chloride and 2-thioalkoxyhydroquinones and oligomers of terephthaloyl chloride and 2-alkoxyhydroquinones with PA 11 implied that the interactions between the blended compounds were poor. FTIR spectra and viscosity measurements confirmed that all the oligomeric structures could self-associate, with effect on the final mechanical properties of the polyamide. The strength of PA 11 in a three-point bending test was increased by the addition of only 1% of LC oligomers to the matrix. The results also showed that the strengthening ability of the oligomers is directly proportional to the total amount of aliphatic carbons. The best strengthening results were obtained with unsubstituted oligomers, random co-oligomers of 2-alkoxy-4-hydroxybenzoic acids, and homo-oligomer of 2-butoxy-4-hydroxybenzoic acid. DSC investigations of a ternary blend of the oligomer of 2-decanyloxy-4-hydroxybenzoic acid, PA 11, and wholly aromatic commercial LC polymer showed the promising compatibilizing effect of the oligomer.

O poli(fluoreto de vinilideno) (PVDF) é um polímero semicristalino que quando cristalizado a partir da fusão à temperaturas acima de 155°C apresenta uma variada morfologia cristalina, constituída por esferulitos anelados, não anelados e mistos. Abaixo dessa temperatura somente os esferulitos anelados são formados. Neste trabalho foi realizado um estudo morfológico do PVDF, procurando verificar a relação entre o tipo de esferulito formado e a fase cristalina predominante em suas lamelas. Foi verificado, por espectroscopia no infravermelho, que os esferulitos anelados apresentam exclusivamente a fase alfa, quando a cristalização ocorre a temperaturas inferiores a 155°C. Temperaturas superiores a essa induzem nessas estruturas uma transformação de fase alfa em gama, que aumenta a quantidade de fase gama com o tempo de cristalização. A taxa com que essa transformação ocorre aumenta com a temperatura de cristalização. Os esferulitos não anelados são constituídos predominantemente pela fase gama, cristalizada diretamente do fundido, com pequenas inclusões de fase alfa. O processo de fusão dos diferentes esferulitos, observado por microscopia ótica (MOLP) e medidas calorimétricas (DSC), mostraram que a temperatura de fusão da fase gama originada da transformação de fase é 8°C superior à daquela cristalizada diretamente do fundido. Micrografias de amostras aquecidas até 186°C e rapidamente resfriadas permitiram visualizar as regiões dos esferulitos anelados que sofreram a transformação de fase alfa em gama, para diferentes tempos e temperaturas de cristalização. Foi realizado, ainda, um estudo morfológico de blendas PVDF/P(VDF-TrFE), com diferentes composições e com o copolímero contendo 72% em mol de VDF. Análises térmicas (DSC) verificaram que os componentes da blenda são imiscíveis na fase cristalina, quando a cristalização ocorre a partir da fusão. Porém, micrografias obtidas por MOLP e MEV indicaram a presença de moléculas do copolímero nas regiões interlamelares dos esferulitos formados durante a cristalização do PVDF. Esse resultado sugere a miscibilidade entre os componentes no estado líquido, e que esta mistura íntima deve permanecer durante a cristalização, resultando na miscibilidade dos componentes na fase amorfa. / Poly(vinylidene fluoride) (PVDF) is a semi crystalline polymer that, when is crystallized from the melt at temperatures above 155°C, it presents a multiform morphology composed of ringed, non-ringed and mixed spherulites. Above this temperature only ringed spherulites are formed. In this work a morphological study of PVDF was performed, endeavoring to investigate the relation between the type of spherulite formed and the dominant crystalline phase in their lamellas. Infrared spectroscopy showed that the ringed spherulites are formed exclusively by the alpha phase when crystallization takes place at temperatures below 155°C. Higher temperatures induce a solid-state alpha in gamma phase transformation in these structures, increasing the amount of gamma phase with crystallization time. The rate at which this transformation takes place increases with crystallization temperature. The non-ringed spherulites consist predominantly of the gamma phase, crystallized from the melt, with small alpha phase inclusions. The melt process of the different spherulites, observed by optical microscopy (MOLP) and calorimetric measurements (DSC) showed that the melt temperature of the gamma phase originated from the phase transition is 8°C higher than that crystallized directly from the melt. Micrographs of samples heated up to 186°C and quickly cooled allowed visualization of the ringed spherulite regions, which underwent the alpha in gamma phase transformation at different crystallization times and temperatures. In addition, it was observed a morphological study of blends, with different compositions and the copolymer containing 72 mol% of VDF. Thermal analysis (DSC) showed that blend components are immiscible on crystalline phase, when the crystallization from the melt occurs. However, micrographs obtained from MOLP and MEV indicated the presence of copolymer on spherulites interlamellar regions, formed during PVDF crystallization. This result suggests miscibility between the components in the liquid state, and this intimate mixture must remain during crystallization, resulting in miscibility of the components in amorphous phase.

Poli(hidroxibutirato) (PHB) é um polímero com um alto potencial de aplicação industrial, pois é biodegradável, tem propriedades físicas semelhantes ao poli(propileno) e é o mais abundante de sua classe, os poli(hidroxialconoatos). Porém, sua rigidez e fragilidade, combinadas com seu elevado custo de produção, têm limitado sua utilização em larga escala. Nesse sentido o PHB pode ser utilizado para o desenvolvimento de novos materiais como blendas, que são mais viáveis em comparação aos métodos de síntese. Estudos de blendas PHB/PVA por solução reportam boa compatibilidade entre os componentes, porém esse processo apresenta baixa produção, já que ampliação de escala é dificultada. Neste trabalho, blendas de PHB/PVA nas composições de 90:10, 75:25 e 50:50 em massa e plastificadas com glicerol foram obtidas por meio de mistura mecânica, utilizando uma extrusora rosca simples. As técnicas de espectroscopia no infravermelho por transformada de Fourier (FTIR), calorimetria exploratória diferencial (DSC), análise térmica dinâmico-mecânica (DMTA) e microscopia eletrônica de varredura (MEV) foram empregadas para estudar a miscibilidade das blendas. Os principais resultados indicam que as blendas são miscíveis: i) deslocamentos de bandas dos espectros de FTIR das blendas nas regiões de 1277 e 1054 cm-1 indicando interações intermoleculares fortes no sistema, como por exemplo polares e ligações de hidrogênio, ii) Tg única e intermediária às Tgs dos polímeros puros observada nas curvas do DMTA para as blendas, e iii) a ausência de duas fases nas imagens do MEV realizadas para as blendas com 90% de PHB após extração em meio aquoso da possível fase rica em PVA. Também foi possível observar que a cristalinidade do PHB não foi afetada significativamente pela adição de PVA como mostrado pelos resultados de DSC e difratometria de raios X (DRX). / Poly(hydroxybutyrate) (PHB) is a polymer with high potential for industrial applications, because it is biodegradable, has similar physical properties to poly (propylene) and is the most abundant in its class, the poly(hydroxyalconoates). However, its rigidity and fragility, combined with its high production cost, have limited its use in large-scale. Thus, PHB could be used to develop new materials as blends, which are more feasible compared to synthesis methods. Studies of PHB/PVA blends via solution shows good compatibility between the components, nevertheless, this process presents low production, since scaling up is hard to do. In this work blends of PHB/PVA in the compositions (w/w) 90/10, 75/25 and 50/50, and plasticized with glycerol were prepared by mechanical mixing using a single screw extruder. Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), dynamic-mechanical thermal analysis (DMTA) and scanning electron microscope (SEM) were used to study the miscibility of the blends. The main results indicate that the blends are miscible: i) shifted bands in FTIR spectrum of the blends in 1277 and 1054 cm-1 indicating strong intermolecular interactions in the system, such as polar and hydrogen bonds; ii) single Tg for the blends and intermediate between those of the pure component polymers observed on the DMTA curves; and iii) absence of two phases in the SEM images of blend with 90% PHB after extraction in aqueous medium of the possible PVA-rich phase. It was also possible to observe that the PHB crystallinity was not significantly affected by the addition of PVA as shown in the results of DSC and x-ray diffraction.

This thesis describes a fundamental study of the miscibility and the nature of the interface between components of core-shell polymer blends using the technique of Fluorescence Resonance Energy Transfer (FRET) coupled with data analysis that involves Monte-Carlo simulations. Our aim in this study was to develop a fundamental methodology to quantitatively determine the width of the interface between the two components in binary polymer blends. At the current state of the art, data analysis of FRET experiments requires translational symmetry. In the system under study, uniform core-shell structures satisfy this criterion. Thus, in this work our focus was directed toward the study of a blend system with a core-shell structure. For this FRET study, I have identified a number of potential donor and acceptor dye pairs that fluoresce in the visible range of the spectrum and can be chemically attached to polymers. Among them, I selected, as the donor and the acceptor, a pair of naphthalimide dyes that have not previously been used for FRET experiments. Model experiments showed that while the fluorescence decay profile of the donor chromophore was exponential in solution, it was not exponential in polystyrene (PS) or poly(methyl methacrylate) (PMMA) films. Thus, I carried out refinements to existing FRET theory to interpret the data generated by using these dyes. Also, I derived a new model to predict the fluorescence intensity of non-exponential decaying donor dyes in core-shell systems. I selected a model system composed of a PS core surrounded by a PMMA shell. The PS core particles were prepared by miniemulsion polymerization to obtain cross-linked PS particles with a narrow size distribution. Seeded emulsion polymerization under starved-fed condition was employed to synthesize monodisperse dye-labeled core-shell particles. The extent of miscibility and the nature of interface between the core and the shell polymers were retrieved from a combined study by Monte-Carlo simulations and analysis of the donor fluorescence intensity decays. Agreement between the retrieved interface thickness and the literature data on PS-PMMA validates the methodology developed here for the use of such donor dyes in FRET studies on polymer blends.

This thesis describes a fundamental study of the miscibility and the nature of the interface between components of core-shell polymer blends using the technique of Fluorescence Resonance Energy Transfer (FRET) coupled with data analysis that involves Monte-Carlo simulations. Our aim in this study was to develop a fundamental methodology to quantitatively determine the width of the interface between the two components in binary polymer blends. At the current state of the art, data analysis of FRET experiments requires translational symmetry. In the system under study, uniform core-shell structures satisfy this criterion. Thus, in this work our focus was directed toward the study of a blend system with a core-shell structure. For this FRET study, I have identified a number of potential donor and acceptor dye pairs that fluoresce in the visible range of the spectrum and can be chemically attached to polymers. Among them, I selected, as the donor and the acceptor, a pair of naphthalimide dyes that have not previously been used for FRET experiments. Model experiments showed that while the fluorescence decay profile of the donor chromophore was exponential in solution, it was not exponential in polystyrene (PS) or poly(methyl methacrylate) (PMMA) films. Thus, I carried out refinements to existing FRET theory to interpret the data generated by using these dyes. Also, I derived a new model to predict the fluorescence intensity of non-exponential decaying donor dyes in core-shell systems. I selected a model system composed of a PS core surrounded by a PMMA shell. The PS core particles were prepared by miniemulsion polymerization to obtain cross-linked PS particles with a narrow size distribution. Seeded emulsion polymerization under starved-fed condition was employed to synthesize monodisperse dye-labeled core-shell particles. The extent of miscibility and the nature of interface between the core and the shell polymers were retrieved from a combined study by Monte-Carlo simulations and analysis of the donor fluorescence intensity decays. Agreement between the retrieved interface thickness and the literature data on PS-PMMA validates the methodology developed here for the use of such donor dyes in FRET studies on polymer blends.