Investigations of comblike polysiloxanes. I. The influence of spacer length on dielectric relaxation studies of aligned samples

Abstract

AbstractDielectric relaxation studies on aligned liquid‐crystalline comblike polysiloxanes are presented. The polymers differ only in the length of the flexible spacer separating the mesogenic side groups from the polysiloxane backbone. The characteristic features of the observed relaxation process as a function of frequency and temperature, in both the liquid‐crystalline and isotropic phases, are described, and the effect of the spacer length is discussed. Within the liquid‐crystalline phase a narrow single loss process is observed, due to the relaxation of the mesogenic side groups around the polymer backbone, whereas in the isotropic phase a much broader loss curve is seen. The transition from an aligned polymer mesophase to the randomly aligned isotropic phase is also studied in detial, and comparison with earlier work on comblike polyacrylate and methacrylate liquid crystals is presented.