Phase transition and liquid crystalline structures of side-chain liquid-crystalline polysiloxanes containing acetoyl group a mesogenic terminal substituent

Polysiloxanes containing acetoy group as a mesogenic terminal substituent were synthesized and the effects of acetoyl group on liquid crystalline properties and structures were investigated. The poly[{omega-{4-(4-(acetoyl)phenoxy carbonyl)phenoxy}}alkyl methyl siloxanes] with different spacer lengths indicate smectic phases in the temperature range between glass transition (T-g and isotropic phase transition (T-i). Smectic A (S-A) phase was observed in each polymer, and additional smectic phase appeared under the S-A phase as spacer lengths increased. The higher ordered smectic phase could be assigned to smectic E-like phase from the X-ray scattering results. The T-i's, enthalpy and entropy changes of the polymers exhibited clearly odd-even effects.