Synthesis and characterization of chiral liquid-crystalline polysiloxanes containing fluorinated units and sulfonic acid groups

Chiral side-chain liquid-crystalline polysiloxanes (PS-1, PS-2, PS-3, PS-4, PS-5, PS-6) bearing fluorinated units and sulfonic acid groups were synthesized with poly(methylhydrogeno)siloxane, cholest-5-en-3-ol(3 beta)-4-(2-propenyloxy)benzoate, and 3-trifluoromethyl-phenyl 3-sulfo-4-undec-10-enoyloxy-benzoate. The effects of fluorinated units and sulfonic acid groups on characteristic of liquid-crystal line properties were studied. PS-1, PS-2, and PS-3 exhibited both smectic and cholesteric mesophases, while PS-4, PS-5, and PS-6 exhibited only cholesteric mesophase. As the polymers contained more fluorinated units and sulfonic acid groups, segregation of the fluorinated segment to the surface and aggregation of hydrogen bonding should occur. Therefore, the highly ordered lamellar mesogen-siloxane matrix systems should be disturbed severely, suggesting that PS-4, PS-5, and PS-6 show no smectic phase. The maximum reflection bands become broad and shifted slightly to long wavelength from PS-1 to PS-6. Copyright (C) 2008 John Wiley & Sons, Ltd.