In this study we synthesized poly(tyrosine) (PTyr) through living ring-opening polymerization of £\-amino acid-N-carboxyanhydride and then blended with poly(4-vinyl pyridine) (P4VP) homopolymer in N, N-dimethylformamide (DMF) and methanol solutions to control the miscibility behavior and the secondary structures of poly(tyrosine). Infrared spectrum analysis suggests that the mixture of PTyr/P4VP possesses strong hydrogen-bonding interaction between the hydroxyl group of PTyr and the pyridine group of P4VP. DSC analyses indicate that these PTyr/P4VP complexes from methanol solution always have higher glass transition temperatures than the corresponding PTyr/P4VP miscible blends obtained from DMF solution. We proposed that the polymer chain behavior of PTyr/P4VP blend from DMF solution is the separated random coil and thus the PTyr chain possesses the random coil secondary structure after solvent evaporation. However, by increasing the hydrogen bonding for PTyr/P4VP complex from methanol solution, inter-polymer complex aggregate is proposed and the corresponding chain behavior enhances the intermolecular hydrogen bonding interaction of PTyr with P4VP that results in the £]-sheet conformation based on Fourier transforms infrared (FTIR), solid state nuclear magnetic resonance (NMR) spectroscopy, and wide-angle X-ray diffraction analyses.

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.

Composites based on binary polymer blends of polystyrene (PS)/poly(ethylene-co-vinyl alcohol) (EVOH) (70/30 wt%) containing natural Montmorillonite, Na-MMTs (Nanomer PGW or Cloisite Na+) and organically modified Montmorillonite clays, OMMTs (Nanomer I.30T, Cloisite 30B or Cloisite 10A) were prepared via melt compounding. The interactions between the polymers and clays were studied using flow micro-calorimetry (FMC). Data obtained from FMC indicated that the probe molecule mimicking EVOH (butan-2-ol) interacted with the MMTs and OMMTs much more strongly than PS. Scanning electron microscopy (SEM) revealed that composites based on binary blends had dispersed/continuous morphologies, in which EVOH was dispersed in a PS matrix. The size of the EVOH droplets in the PS matrix increased with increasing clay loading. Transmission electron microscopy (TEM) and wide angle X-ray diffraction (WAXD) were used to determine the extent of dispersion and location of clay in the PS/EVOH/clay composites. These techniques confirmed the formation of intercalated clay structures. As predicted by FMC, the clay platelets were selectively located in the EVOH phase, independent of the blending sequence and the type of organic modifier in the OMMT. Composites containing OMMTs showed better dispersion of platelets within the EVOH phase than those containing Na-MMTs. Differential scanning calorimetry (DSC); showed the crystallisation behaviour of EVOH to depend on the clay loading and the nature of the organic modifier in the OMMT. Nanomer PGW, Cloisite Na+ and Cloisite 30B acted as weak nucleating agents. In contrast, Nanomer I.30T and Cloisite 10A significantly hindered the crystallisation of EVOH in the blends due to the restriction of chain segment mobility. Dynamic mechanical thermal analysis (DMTA) confirmed that the presence of clay increases the storage modulus of the composites compared to an unfilled blend. In addition, the improvement in storage modulus reflected the dispersion state of the different clays and their interaction with the polymers of the blend. Ternary-blend based composites were formed by adding poly(styrene-co-acrylonitrile) (SAN) to the composites based on binary PS/EVOH blends. This resulted in a finer dispersion of the EVOH phase and the development of a core-shell morphology, in which SAN encapsulated and formed shells around EVOH droplets. In contrast to binary blend composites, the clay platelets were found at the interface between SAN and EVOH in the ternary blends.

<p> Self-consistent field theory (SCFT) is a well established theoretical framework for describing the thermodynamics of block copolymer melts and blends. Combined with numerical methods, the SCFT can give useful and accurate predictions regarding the phase behavior of polymer blends. </p> <p> We have applied SCFT to study the phase behavior of blends composed of diblock copolymers (AB) and homopolymers (C). Two cases are studied in detail. In the first case the homopolymers have a repulsive interaction to the diblock copolymers. We found an interesting feature in the phase diagram that there exists a bump of the phase boundary line when A is the majority-component. In the second case, the homopolymers have an attractive interaction to one of the blocks of the diblock copolymers. A closed-loop of microphase separation region forms for strong interactions. For both cases, we have investigated the effects of homopolymer concentration, homopolymer chain length, and monomer-monomer interactions, on the phase behavior of the system. </p> <p> We also investigated micelle formation in polymer blends. Diblock copolymers (AB) blended with homopolymers (A) can self-assemble into lamellar, cylindrical and spherical micelles. The critical micelle concentrations for different geometries are determined using self-consistent field theory. The effect of varying copolymer block asymmetry, homopolymer molecular weight and monomer-monomer interactions on micelle morphology are examined. \\Then the blends are confined between two flat surfaces, the shape of the micelles may differ from that of the bulk micelles. We study the shape variation of a. spherical micelle under confinement and its dependence on the film thickness and surface selectivity. </p> / Thesis / Doctor of Philosophy (PhD)

No description available.

Este trabalho apresenta o estudo de vidros e vitro-cerâmicas oxifluoretos de composição PbGeO3 CdF2 PbF2 (Fluorgermanatos de cádmio e chumbo) e de blendas poliméricas formadas entre o eletrólito polimérico PEO:LiC104 (Poli-óxido de eltileno com perclorato de lítio) e o polímero condutor POMA (Poli-orto metoxianilina). Foram utilizadas as técnicas de ressonância magnética nuclear (RMN), ressonância paramagnética eletrônica (RPE), calorimetria exploratória diferencial (DSC) e impedância complexa. Dentre várias aplicações, estes materiais são importantes devido ao grande potencial como eletrólitos sólidos. Este estudo tem como principal objetivo esclarecer os mecanismos de transporte iônico do flúor e do lítio. Os resultados mostraram que os mecanismos da condução iônica nos vítreos oxifluoretos são caracterizados diferentemente em cada região de temperatura estudada. Em baixas temperaturas (T&#60;300K), o processo de relaxação foi atribuído às excitações de baixas-frequências dos modos desordenados. Acima de 300K, porém abaixo da temperatura de transição vítrea, os movimentos do flúor modulam as interações dipolares F-F. As vitro-cerâmicas, obtidas através de tratamentos térmicos dos vidros de oxifluoretos, são materiais compósitos onde nano ou micro-cristais estão dispersos na matriz vítrea. Os resultados de RMN mostraram no intervalo 100 800K, pelo menos três processos de relaxação, que foram associados com (i) movimentos difusionais dos íons de flúor nos cristais de &#946;-PbF2, (ii) mobilidade iônica na matriz vítrea e (iii) íons de flúor de baixa mobilidade (provavelmente PbGeO3-xFx). Os resultados de RMN 1H mostraram que os tempos de correlação associados aos movimentos das macromoléculas nas blendas poliméricas xii são comparáveis aos encontrados na literatura para o PEO/PMMA. A fim de se garantir resultados reprodutíveis, um cuidadoso método de preparação deve ser seguido, assegurando a estabilidade química e a homogeneidade da blenda / This work reports the study of oxifluorides glasses and glass-ceramics of composition PbGeO3 CdF2 PbF2 (Lead cadmium fluorgermanate) and blends formed by the polymer electrolyte PEO:LiC104 (poly etilene oxide and lithium perclorate) and the conducting polymer POMA (poly ortho methox aniline). Nuclear magnetic resonance (NMR), electron paramagnetic resonance (EPR), differential scanning calorimetry (DSC) and complex impedance techniques were used. Among several applications, these materiais are important as solid electrolytes. The main objective of this work is to study the fluor or lithium ionic transport mechanisms. Results show that the ionic conduction mechanism in oxifluoride glass systems is characteristic of each temperature region. In low temperatures (T &#60; 300K), the relaxation processes were attributed to low-frequency excitations of disorder modes intrinsic to the glassy state of mater. Above 300 K and below of the glass transition temperature the fluorine motions modulate the dipolar F-F interactions. The glasscerarnics, produced form their respective glasses, are composite materiais where nano- or micro-crystals are dispersed on the glassy matrix. The NMR results, in the range 100-800 K, evidenced three separate relaxation process: (i) diffusional motions of fluorine ions in &#946;-PbF2 crystals; (ii) fluorine mobility in the glass matrix and (iii) fluorine ions of low mobility (probably PbGeO3-xFx). The i ll NMR results shown that the correlation time values, associated to the polymeric chains motion in polymer blends, are comparable to those found for PEO/PMMA. In order to get reproducible results, a careful sample preparation process must be undertaken to ensure chemical stability and blend homogeneity.

Este trabalho apresenta o estudo de vidros e vitro-cerâmicas oxifluoretos de composição PbGeO3 CdF2 PbF2 (Fluorgermanatos de cádmio e chumbo) e de blendas poliméricas formadas entre o eletrólito polimérico PEO:LiC104 (Poli-óxido de eltileno com perclorato de lítio) e o polímero condutor POMA (Poli-orto metoxianilina). Foram utilizadas as técnicas de ressonância magnética nuclear (RMN), ressonância paramagnética eletrônica (RPE), calorimetria exploratória diferencial (DSC) e impedância complexa. Dentre várias aplicações, estes materiais são importantes devido ao grande potencial como eletrólitos sólidos. Este estudo tem como principal objetivo esclarecer os mecanismos de transporte iônico do flúor e do lítio. Os resultados mostraram que os mecanismos da condução iônica nos vítreos oxifluoretos são caracterizados diferentemente em cada região de temperatura estudada. Em baixas temperaturas (T&#60;300K), o processo de relaxação foi atribuído às excitações de baixas-frequências dos modos desordenados. Acima de 300K, porém abaixo da temperatura de transição vítrea, os movimentos do flúor modulam as interações dipolares F-F. As vitro-cerâmicas, obtidas através de tratamentos térmicos dos vidros de oxifluoretos, são materiais compósitos onde nano ou micro-cristais estão dispersos na matriz vítrea. Os resultados de RMN mostraram no intervalo 100 800K, pelo menos três processos de relaxação, que foram associados com (i) movimentos difusionais dos íons de flúor nos cristais de &#946;-PbF2, (ii) mobilidade iônica na matriz vítrea e (iii) íons de flúor de baixa mobilidade (provavelmente PbGeO3-xFx). Os resultados de RMN 1H mostraram que os tempos de correlação associados aos movimentos das macromoléculas nas blendas poliméricas xii são comparáveis aos encontrados na literatura para o PEO/PMMA. A fim de se garantir resultados reprodutíveis, um cuidadoso método de preparação deve ser seguido, assegurando a estabilidade química e a homogeneidade da blenda / This work reports the study of oxifluorides glasses and glass-ceramics of composition PbGeO3 CdF2 PbF2 (Lead cadmium fluorgermanate) and blends formed by the polymer electrolyte PEO:LiC104 (poly etilene oxide and lithium perclorate) and the conducting polymer POMA (poly ortho methox aniline). Nuclear magnetic resonance (NMR), electron paramagnetic resonance (EPR), differential scanning calorimetry (DSC) and complex impedance techniques were used. Among several applications, these materiais are important as solid electrolytes. The main objective of this work is to study the fluor or lithium ionic transport mechanisms. Results show that the ionic conduction mechanism in oxifluoride glass systems is characteristic of each temperature region. In low temperatures (T &#60; 300K), the relaxation processes were attributed to low-frequency excitations of disorder modes intrinsic to the glassy state of mater. Above 300 K and below of the glass transition temperature the fluorine motions modulate the dipolar F-F interactions. The glasscerarnics, produced form their respective glasses, are composite materiais where nano- or micro-crystals are dispersed on the glassy matrix. The NMR results, in the range 100-800 K, evidenced three separate relaxation process: (i) diffusional motions of fluorine ions in &#946;-PbF2 crystals; (ii) fluorine mobility in the glass matrix and (iii) fluorine ions of low mobility (probably PbGeO3-xFx). The i ll NMR results shown that the correlation time values, associated to the polymeric chains motion in polymer blends, are comparable to those found for PEO/PMMA. In order to get reproducible results, a careful sample preparation process must be undertaken to ensure chemical stability and blend homogeneity.

This investigation presents research on the characteristic properties of Nylon66 and poly(ethylene naphthalate) (Ny66/PEN), and poly(butylene terephthalate) and poly(ethylene naphthalate) (PBT/PEN) blends with several weight compositions made by melt blending, by the use of 13C and 1H Nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Scanning electron microscopy (SEM), Differential scanning calorimetry (DSC) and Dynamic mechanical thermal analysis (DMTA), X-ray diffraction (X-RD), tensile, impact and stress relaxation tests. Ny66/PEN blends including several additives do not improve the miscibility of the constituent polymers and show lower tensile strength than those of homopolymers. However, PBT/PEN blends reveal improved tensile strengths of the blends between the ROM and MROM predictions lines with more than 50 % volume fraction of PEN. On the other hand, NMR spectra show no evidence of interchange reaction in both Ny66/PEN and PBT/PEN blends. SEM micrographs of fracture surfaces in PBT/PEN blends reveal a very small (sub-micron) domain size in contrast to large domains in Ny66/PEN blends, which indicates partial miscibility of PBT and PEN. DSC and DMTA demonstrate partial miscibility of PBT/PEN blends by the change of Tgs of each component according to the weight proportions of the constituent polymers. Stress relaxation tests for the specimens of PBT/PEN blends and the homopolymers, using the Taguchi method of experimental design, determine that the most significant factor is the temperature, followed by PEN content and then the initial stress, and interaction effects between factors are insignificant. To fit the relaxation curves of the PBT/PEN blends and the homopolymers at different temperatures, PEN contents and initial stresses, four different equations have been used. The coefficients of the equation that fit best are used to predict the relaxation behaviour of PBT/PEN blends at a temperature between 30C and 60C, and at the initial stresses of 7 MPa.

This investigation presents research on the characteristic properties of Nylon66 and poly(ethylene naphthalate) (Ny66/PEN), and poly(butylene terephthalate) and poly(ethylene naphthalate) (PBT/PEN) blends with several weight compositions made by melt blending, by the use of 13C and 1H Nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Scanning electron microscopy (SEM), Differential scanning calorimetry (DSC) and Dynamic mechanical thermal analysis (DMTA), X-ray diffraction (X-RD), tensile, impact and stress relaxation tests. Ny66/PEN blends including several additives do not improve the miscibility of the constituent polymers and show lower tensile strength than those of homopolymers. However, PBT/PEN blends reveal improved tensile strengths of the blends between the ROM and MROM predictions lines with more than 50 % volume fraction of PEN. On the other hand, NMR spectra show no evidence of interchange reaction in both Ny66/PEN and PBT/PEN blends. SEM micrographs of fracture surfaces in PBT/PEN blends reveal a very small (sub-micron) domain size in contrast to large domains in Ny66/PEN blends, which indicates partial miscibility of PBT and PEN. DSC and DMTA demonstrate partial miscibility of PBT/PEN blends by the change of Tgs of each component according to the weight proportions of the constituent polymers. Stress relaxation tests for the specimens of PBT/PEN blends and the homopolymers, using the Taguchi method of experimental design, determine that the most significant factor is the temperature, followed by PEN content and then the initial stress, and interaction effects between factors are insignificant. To fit the relaxation curves of the PBT/PEN blends and the homopolymers at different temperatures, PEN contents and initial stresses, four different equations have been used. The coefficients of the equation that fit best are used to predict the relaxation behaviour of PBT/PEN blends at a temperature between 30C and 60C, and at the initial stresses of 7 MPa.

This investigation presents research on the characteristic properties of Nylon66 and poly(ethylene naphthalate) (Ny66/PEN), and poly(butylene terephthalate) and poly(ethylene naphthalate) (PBT/PEN) blends with several weight compositions made by melt blending, by the use of 13C and 1H Nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Scanning electron microscopy (SEM), Differential scanning calorimetry (DSC) and Dynamic mechanical thermal analysis (DMTA), X-ray diffraction (X-RD), tensile, impact and stress relaxation tests. Ny66/PEN blends including several additives do not improve the miscibility of the constituent polymers and show lower tensile strength than those of homopolymers. However, PBT/PEN blends reveal improved tensile strengths of the blends between the ROM and MROM predictions lines with more than 50 % volume fraction of PEN. On the other hand, NMR spectra show no evidence of interchange reaction in both Ny66/PEN and PBT/PEN blends. SEM micrographs of fracture surfaces in PBT/PEN blends reveal a very small (sub-micron) domain size in contrast to large domains in Ny66/PEN blends, which indicates partial miscibility of PBT and PEN. DSC and DMTA demonstrate partial miscibility of PBT/PEN blends by the change of Tgs of each component according to the weight proportions of the constituent polymers. Stress relaxation tests for the specimens of PBT/PEN blends and the homopolymers, using the Taguchi method of experimental design, determine that the most significant factor is the temperature, followed by PEN content and then the initial stress, and interaction effects between factors are insignificant. To fit the relaxation curves of the PBT/PEN blends and the homopolymers at different temperatures, PEN contents and initial stresses, four different equations have been used. The coefficients of the equation that fit best are used to predict the relaxation behaviour of PBT/PEN blends at a temperature between 30C and 60C, and at the initial stresses of 7 MPa.