Relaxation in domains:: Structure and segmental dynamics of LC/I diblock copolymers

A series of block copolymers consisting of an isotropic (polystyrene) block and a side-chain liquid crystalline block (LC) have been studied using small-angle X-ray scattering and dielectric spectroscopy. The triblock copolymer (PS-LC-PS) displays an order-to-order transition (OOT) together with the isotropic/nematic transition of the LC phase. The series of diblock copolymers show no clear OOT but the phase diagram differs from that of non-LC block copolymers. The segmental dynamics as measured with dielectric spectroscopy is dominated by the alpha and delta relaxation of the LC block. Both display a WLF like temperature dependence. The relaxation times are influenced by the constraints of the nanoscale domains. They are decreased for the LC confined in the domain as compared to the LC in the continuous matrix.