Dipolar motions and phase transitions in a side-chain polysiloxane liquid crystal. A study by thermally stimulated depolarization currents

The relaxation mechanisms present in a side-chain liquid crystalline polyme r have been studied by Thermally Stimulated Depolarization Currents (t.s.d. c.), in a wide temperature range covering the glassy state, the glass trans ition region, and the liquid crystalline phase. The thermal sampling proced ure was used to decompose the complex relaxations into its narrowly distrib uted components. Three relaxation mechanisms were observed in this polymer: a relaxation below the glass transition temperature that is broad and exte nds from -150 degrees C up to -110 degrees C, the glass transition relaxati on whose maximum intensity appears at similar to 20 degrees C, and a relaxa tion above the glass transition temperature, in the liquid crystalline phas e. The attribution of these relaxations at the molecular level is discussed . (C) 1999 John Wiley & Sons, Inc.