Abstract

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 (<i>E</i>) 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 <i>E</i>-field (3750 V cm<sup>−1</sup>) 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.

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