DIELECTRIC STUDY OF FERROELECTRIC SIDE-CHAIN LIQUID-CRYSTALLINE POLYSILOXANES WITH BROAD TEMPERATURE RANGES OF THE CHIRAL SMECTIC-C PHASE-1- STRUCTURE DEPENDENCE OF DIELECTRIC-RELAXATION

The dielectric behavior of a series of ferroelectric side-chain liquid crystalline polysiloxanes containing 1-3 oligooxyethylene units as sp acers, and -1-butyl[[(4-hydroxy-biphenyl-4'-yl)]carbonyl]oxy] benzoate or [[(4-hydroxy-biphenyl-4'-yl)carbonyl]oxy]-3-fluoro benzoate side g roups was studied by broadband dielectric spectroscopy. The increase o f the spacer length, and incorporation of a strong dipole moment fluor o-substituent into the mesogenic group, resulted in a decrease of the relaxation activation energy and an increase in the intensity of the r elaxation. Moreover, the relaxation peak of the Goldstone mode has onl y been observed for the FLCP with a lateral fluoro-substituent. The re lationship between the thermal dynamic behavior and chemical structure is discussed in detail. Furthermore, analysis of the dielectric relax ation behavior of these FLCPs showed that the molecular relaxations co uld be described by the Cole-Cole equation. (C) 1996 John Wiley & Sons , Inc.