Analysis of grain structure in partially ordered block copolymers by depolarized light scattering and transmission electron microscopy

The grain structure in lamellar block copolymer samples undergoing a disorder-to-order transition was studied by a combination of depolarized light scattering (DPLS) and transmission electron microscopy (TEM). The 4-fold symmetry of the DPLS profiles indicated the presence of anisotropic grains. A pattern recognition algorithm for analyzing the TEM micrographs of samples partially filled with anisotropic, ordered grains was developed. The volume fractions of sample occupied by ordered grains determined from light scattering and electron microscopy are in reasonable agreement. Both methods indicate that, on average, the characteristic length of the grains in the direction perpendicular to the lamellar planes was a factor of 2 larger than that in the plane of the lamellae. The absolute magnitudes of grain sizes determined by light scattering are about 50% larger than those determined by microscopy.