Thermal and Dielectric Behavior of Liquid-Crystalline Polybutadiene-Diols with Mesogenic Groups in Side Chains

Ordered polybutadiene diols (LCPBDs) with the comb-like architecture were prepared by radical reaction of a thiol with azobenzene mesogenic group with double bonds of telechelic HO-terminated polybutadiene (PBD); several polymers with various initial molar ratios of thiol to double bonds of PBD, R0, in the range from 0 to 1 were prepared. DSC, polarizing microscopy, WAXS and dielectric relaxation spectroscopy (DRS) were employed to investigate their thermal and dielectric behavior in relation to morphology. DRS of the LCPBDs have revealed both collective and individual dynamic motions of molecules. Secondary beta- and segmental alpha-relaxation were observed in unmodified PBD. In the LCPBDs, two secondary gamma-and beta-and two high-temperature alpha- and delta-relaxations were observed and assigned to specific molecular motions; all relaxations were analyzed and discussed in terms of time scale (Arrhenius diagram), magnitude (relaxation strength) and shape of the response.