Nematic and domain order parameters for partially oriented isotropic/liquid crystalline diblock copolymers: A dielectric spectroscopy study

Dielectric relaxation in a liquid crystalline (LC) side chain polymer and in a series of diblock copolymers with polystyrene is investigated using dielectric spectroscopy. The block copolymer morphology is cylindrical with the LC block forming the continuous matrix. Two processes are found in the nematic state with their relative dielectric relaxation strength strongly dependent on block copolymer composition. The spectra are described using the concept of a local order parameter S and a domain order parameter SD. Application of electric or mechanical fields induce a homeotropic orientation of the nematic domains in the homopolymer without significantly influencing the local order parameter. The block copolymers display a spontaneous orientation even in thick films (d < 300 nm)