Broad Temperature Range Of Chiral Smectic C Phase In Some Ferroelectric Side-Chain Liquid Crystalline Polysiloxanes Containing Oligooxyethylene Spacers

ABSTRACTThe Mesomorphic behaviors of some ferroelectric liquid crystalline monomers and side-chain polysiloxanes studied by X-ray diffraction Measurement, differential scanning calorimeter and polarizing Microscope. All obtained polymers exhibit wide temperature range of chiral smectic C phase including room temperature.These Mesogenic structures contain oligooxyethylene spacers and (S)-2-Methyl-l -butyl chiral tail via a three phenyl ester linkage (i.e. -Ph-COO-Ph-Ph- or -Ph-Ph-COO-Ph-). Two series of monomers with different biphenyl group linkage position were compared. One shows a novel twisted smectic A phase, in addition to the liquid crystalline sequence (Ch→SA→Sc*) obtained between cholesteric phase and smectic A phase. It also presents an unusual smectic A and chiral smectic C phase.All the prepared polymers present smectic Mesomorphism. As the unit of flexible oligooxyethylene spacers increases, the clearing temperature decreases and the stability of the smectic phase also increases.