Electric Field FT-IR: Analysis of a Liquid Crystalline Polymer

Fourier transform infrared spectroscopy in a reflective mode has been utilized to study the dynamics of molecular structure in a polymeric liquid crystalline melt. The experimental setup included a thermo-electric cell which allows heating, melting of the sample, and also application of an electric () field during spectroscopic observation. It was therefore possible to monitor orientation of dipolar groups as a function of time during thermal and electrical treatments. The material studied was a liquid crystalline copolyester, and orientation was monitored through absorbance associated with stretching of carbonyl bonds. Measurements taken on a melt of this material reveal an orientational response of carbonyl groups which begins immediately upon application of a relatively low -field (3750 V cm⁻¹) and continues over a period of approximately one hour. It was somewhat surprising that a measurable change in dipolar orientation was observed. Cooperative dipolar phenomena and the torque-transmitting elasticity of the mesomorphic fluid are thought to be important factors in the observed behavior.