Phase behavior and defect structures in ordered block copolymers

Block copolymers have the potential of performing complex functions, which makes them ideal for various novel applications. In this work, our goal is to understand the physical origins of their complex responses and to be able to control them to produce useful results. We used a combination of depolarized light scattering (DPLS) and transmission electron microscopy (TEM) to study the grain structure in lamellar block copolymer samples undergoing a disorder-to-order transition. We developed a pattern recognition algorithm based on a local Fourier transform to analyze TEM micrographs from samples partially filled with anisotropic, ordered grains.; We have observed birefringence and depolarized light scattering patterns with 2-fold symmetry from a cylindrical diblock copolymer solution that was ordered under shear flow. We have developed a theory to account for such 2-fold symmetric scattering patterns, based on a model that assumes an anisotropic orientation distribution of ellipsoidal grains in the sample.; We investigated the structure and phase behavior of block copolymer melts near the sphere-cylinder boundary. We showed that the phase behavior, near the sphere-cylinder boundary, depends on all three thermodynamic parameters: f, chi, and N and not just f and (chiN), as is usually the case. Here f is the volume fraction of one of the blocks, chi is the Flory-Huggins interaction parameter between the blocks, and N is the total number of monomers in the block copolymer chain. This dependence on f, chi, and N is ascribed to fluctuation effects and the presence of micelles in the disordered phase.; We showed first-time depolarized light scattering and polarized optical microscopy evidence of a nematic texture obtained from ordered styrene-isoprene (SI) diblock copolymer melts. These newly observed micron-sized, liquid crystal-type defects were in fact global, 3-dimensional, and kinetically stable. Shearing such textures produced excellent and rapid alignment.; We investigated the effect of molecular architecture on the grain growth kinetics of star block copolymers. We employed a local Fourier transform procedure to analyze TEM data obtained from these fully ordered samples containing anisotropic grains.