Dielectric, nuclear magnetic resonance and electron spin resonance studies of relaxation processes in a liquid-crystalline polyester
- 1 January 1985
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Faraday Discussions of the Chemical Society
- Vol. 79, 191-199
- https://doi.org/10.1039/dc9857900191
Abstract
The molecular dynamics of the polyester (—OC—[Ph]3—CO—O—[CH2–CH2—O—]4)n, which has a liquid-crystalline smectic C (SC) phase, have been investigated by the e.s.r. spin-probe, dielectric relaxation and carbon-13 solid-state n.m.r. techniques. The low-temperature, high-frequency γ relaxation preserves the characteristics of the local in-chain motions of polyethers. The apparent activation energy corresponds to a very simple flexible structure. The most likely mechanism of this γ relaxation might be the local tg+t ↔ tg–t transition in the central ‘ether’ units. Two β relaxation processes were found: the βL relaxation is believed to be caused by diffusional segmental motion of the flexible spacers located in isolated amorphous isotropic regions of the material and the βU process is associated with the ‘ether’ sequences located in the glassy SC domains. The increasing rate of rotation of the phenyl rings about their C1—C4 axis is related to the crystal ↔ SC transition. Note that this motional process of the phenyl rings does not alter the mean orientation of the mesogenic groups.Keywords
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