(265b) Effect of Crosslinking on the Structure and Thermodynamics of Block Copolymers

The effect of crosslinking on the structure and thermodynamics of lamellar and cylindrical poly(styrene-block-isoprene) copolymers was studied using small angle X-ray scattering (SAXS), depolarized light scattering (DPLS) and transmission electron microscopy (TEM). The selective crosslinking of the poly(isoprene) block took place either in the disordered state, in an isotropic ordered state, or in a shear-aligned ordered state. The order-disorder transition temperature for various block copolymer networks was determined as function of crosslinking density. Using DPLS and TEM, the grain structure as a function of crosslinking density was studied. It was found that crosslinking in the disordered phase promoted the formation of large, anisotropic grains for a specific range of crosslinking densities. For the shear-aligned samples crosslinked in the ordered phase, the recovery of alignment was determined using SAXS and DPLS.