Relaxation of the Induced Orientational Order in the Isotropic Phase of Nematic Polymer

TL;DR

This study investigates the relaxation dynamics of orientational order in the isotropic phase of a nematic polymer, revealing multiple exponential relaxation processes and their temperature-dependent behavior.

Contribution

It is the first to analyze the relaxation of electric birefringence in a mesogenic polymer, identifying multiple relaxation processes and their temperature evolution.

Findings

Two main relaxation processes dominate above the phase transition.

Dielectric spectroscopy distinguishes side group rotation from main chain motion.

Relaxation processes interchange over a fifty-degree temperature range.

Abstract

Orientational dynamics in the isotropic phase of a comb-shaped nematic polymer with mesogenic and functional side groups was studied using the Kerr effect and dielectric spectroscopy. For the first time, it was found that in a mesogenic polymer, in contrast to low-molecular-weight mesogens, the relaxation of the electric birefringence of a melt above the temperature of the nematic-isotropic phase transition can be presented by a sum of several exponential processes, two of which play a decisive role. These main processes replace each other in a temperature range of about fifty degrees. Dielectric spectroscopy also made it possible to distinguish two processes of orientational relaxation: the first is due to rotation of the side mesogenic groups, and the second is associated with motion of the main chain segments.