Molecular Dynamics of Liquid Crystalline Side Chain Polymers of Different Types

We present a dielectric spectroscopic study of a newly synthesized liquid crystalline side chain polymer with a methacrylate main chain. By a comparison with analogous compounds where only the α-substituent at the main chain is varied we examine the influence of the polymer backbone on the relaxation processes in the different orientations. The main results are: the 6-relaxation has a non-Arrhenius-like temperature-dependence of the relaxation-frequencies; its relaxation time distribution is broadened in the sequence acrylate-methacrylate-chloroacrylate; the activation energy increases in the same sense; the main chain substituent has no effect on the relaxation strength, which is only determined by the longitudinal dipole moment; the α-relaxation for the methacrylate shows a nearly temperature-independent relaxation frequency near the clearing point and a splitting at lower temperatures-both effects have not been observed so clearly for other side chain polymers. Some molecular interpretations for these phenomena will be discussed.