Synchrotron X-Ray Scattering Studies on Self-Assembled and Mechanically-Deformed Morphologies of Functional Polymers

Abstract

Morphological and structural details of polymeric materials were investigated by using X-ray scattering analysis. Correlations between material properties and their structure were investigated. Main chain stereoregularity effect on material properties and structures were investigated. New analysis method for void scattering was developed and presented. In Chapter I, general introduction of X-ray scattering methods is given. Advantages of using X-ray scattering over microscopic techniques were explained. In Chapter II, various molecular weight -conjugated donor-acceptor polymers based on thiadiazole and thiophene units have been investigated in the aspects of nanoscale film morphology and digital memory performance. Interestingly, all polymers reveal excellent n-type digital permanent memory characteristics, which are governed by the combination of Ohmic and trap-limited space charge limited conductions via hopping process using thiadiazole and thiophene units as charge traps and stepping stones. The digital memory performance is significantly influenced by the film morphology details that vary with the polymer molecular weight as well as the film thickness. Higher population of face-on structure formation, as well as higher molecular weight provides wider film thickness window of digital memory operation. Overall, -conjugated PBTDzTV polymers are suitable for the production of high-performance programmable n-type permanent memory devices with very low power consumption. In Chapter III, A series of brush block copolymers (BBCPs) consisting of poly(decyl glycidyl ether) (PDGE) and poly(10-hydroxyldecyl glycidyl ether) (PHDGE) blocks, having four different types of chain tacticity, i.e., [at-PDGE]-b-[at-PDEGE], [at-PDGE]-b-[it-PDEGE], [it-PDGE]-b-[at-PDEGE], and [it-PDGE]-b-[it-PDEGE], where the it and at represent isotactic and atactic chains, respectively, was investigated in the aspects of thermal properties and nanoscale film morphology. The corresponding homopolymers, i.e., at-PDGE, it-PDGE, at-PHDGE, and it-PHDGE, were also investigate for use in comparison with the BBCPs. PDGE homopolymers were significantly promoted in phase transitions and morphological structure formation by the isotacticity formation. In particular, it-PDGE was found to form only horizontal multibilayer structure with monoclinic lattice in thin films, which was driven by the bristles’ self-assembling ability and enhanced by the isotacticity. However, PHDGE homopolymers were found to reveal somewhat different behaviors in phase transitions and morphological structure formation by the tacticity control because of the additional presence of hydroxyl group in the bristle end as an H-bonding interaction site. The H-bonding interaction could be enhanced by the isotacticity formation. it-PHDGE homopolymer showed only horizontal multibilayer structure, which was different from the formation of a mixture of horizontal and tilted multibilayer structures in at-PHDGE. The structural characteristics were further significantly influenced by the diblock formation and the tacticity of the counterpart block. Due to the strong self-assembling characteristics of the individual block components, all BBCPs formed separate crystals rather cocrystals. The isotacticity always promoted to form better quality morphological structure in terms of lateral ordering and orientation. In Chapter IV, the void formations of polypropylene specimen during mechanical deformation and their structural features and growth have been investigated. To examine such void formations and growths, conventional integral breadth (IB) method as a qualitative approach has been adopted from the literature. To overcome severe limits of the IB method and to get more detailed void features, we have developed new quantitative analysis methods. The newly developed void analysis methods have been developed by utilizing form factor analysis methods, and verified to be applicable for the characterization of void formation and growth. In particular, the mechanical deformation induced void formation and growth in polypropylene have been investigated in detail.