Comparison of the molecular dynamics of a liquid crystalline side group polymer revealed from temperature modulated DSC and dielectric experiments in the glass transition region

Temperature modulated DSC (TMDSC) in the frequency range from 10–3 Hz to 3.4 10–2 Hz and dielectric spectroscopy in the frequency range from 10–2 Hz to 106 Hz is employed to analyze the temperature dependence of the relaxation rates of the α- and of the δ-relaxation of a liquid crystalline polymethacrylate having a derivative of (p-alkoxy-phenyl)-benzoate as mesogenic unit in the side group. Especially the molecular assignment of the α-relaxation was discussed controversial in the literature up to now. By applying a temperature derivative method it was found that the temperature dependencies of the relaxation rates of the dielectric α-relaxation and of the dynamic glass transition measured by TMDSC can be described by Vogel/Fulcher/Tammann laws with the same Vogel temperature. Therefore it is argued that the dielectric α-relaxation of liquid crystalline polymers is rather due to the dynamic glass transition related to the segmental dynamics of the backbone than to the transverse dipole component of the mesogenic unit.