Synthesis of ferroelectric liquid crystalline polysiloxanes containing (S)-2-methylbutyl 4-alkyloxybiphenyl-4′-carboxylate and (2S, 3S)-2-chloro-3-methylpentyl 4-alkyloxybiphenyl-4′-carboxylate

The synthesis of side-chain liquid crystalline polysiloxanes containing (S)-2-methylbutyl-4-alkyloxybiphenyl and (2S, 3S)-2-chloro-3-methylpentyl 4-alkyloxybiphenyl-4′-carboxylate moieties as mesogenic units and aliphatic spacers containing respectively three to eleven methylene units is presented. Differential scanning calorimetry, optical polarizing microscopy and X-ray diffraction measurements reveal chiral smectic mesomorphism for most of the obtained polymers. Two polysiloxanes that contain respectively three methylene units in their spacers exhibit an enantiotropic smectic A phase or no mesophase. Four polysiloxanes that contain respectively five, six and eleven methylene units in their spacers exhibit enantiotropic smectic A and chiral smectic C phases. The results seem to demonstrate that the tendency toward chiral smectic C mesomorphism increases with increasing spacer length. Incorporation of a chloro-containing chiral end group into the mesogenic core of a polymer will decrease the thermal stability of the mesophase formed.