THERMALLY STIMULATED CURRENT AND DSC STUDIES OF THE DUAL GLASS TRANSITIONS IN SIDE-CHAIN LIQUID-CRYSTALLINE COPOLYSILOXANES CONTAINING 4-[(S)-2-METHYLBUTOXY]PHENYL 3-CHLORO-4-ALKENYLOXYBENZOATE SIDE-GROUPS

The synthesis of side-chain liquid crystalline copolysiloxanes contain ing ethylbutoxy]phenoxycarbonyl]-2-chlorophenoxy]alkyl side groups is presented. Differential scanning calorimetry, optical polarizing micro scopy and X-ray diffractometry reveal smectic mesomorphism for most of the obtained polymers. The copolysiloxane with three methylene units in the spacer is the only one showing no mesomorphic property. The oth er four copolysiloxanes, containing four, five, six or eleven methylen e units in the spacer, display a smectic A phase. All of the obtained polymers present dual glass transition behavior by both DSC and therma lly stimulated current (TSC) techniques. The first glass transition (T -g1) at lower temperature is due to the segmental motions of the polys iloxane backbone, while the second glass transition (T-g2) is due to t he cooperative relaxation motions of spacers and mesogenic units.