SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF CHIRAL SMECTIC-C AND SMECTIC-A POLY(VINYL ETHER)S

A new series of chiral liquid-crystalline poly(vinyl ether)s was synthesized by cationic polymerization of the corresponding vinyl ether monomers. They consisted of a biphenyl mesogenic unit bearing an (S)-2-methylbutyl chiral substituent and spaced via an alkyl segment of varying number x of methylene groups. Different initiators and experimental conditions were used for the polymerization reactions. All the samples were semicrystalline, and smectic C and A sequential mesophases were formed in polymers comprising a sufficiently long spacer segment (x > 8). X-ray diffraction measurements were performed on unoriented specimens. In the smectic C phase, the occurrence of different orders of X-ray reflection on the smectic layers enabled drawing of the electron density profiles along the layer normal. By simple model considerations it was possible to choose the most physically acceptable one and to identify the low temperature mesophase as double layer smectic C.