INFLUENCE OF BACKBONE TACTICITY ON THERMOTROPIC PROPERTIES OF SIDE-CHAIN LIQUID-CRYSTAL POLYMETHACRYLATES

In order to study the tacticity effect of the backbone on the thermotr opic properties of side-chain Liquid crystalline (SCLC) polymers, the synthesis of four polymethacrylates with different tacticities and bea ring methoxy biphenyl mesogenic groups was carried out. Homopolymers w ere obtained upon photopolymerisation at low temperature of two mesoge nic methoxy biphenyl monomers, with and without ethylene oxide spacer. Methacrylic acid copolymers were obtained by grafting the same mesoge nic groups onto 92% syndiotactic or atactic polymethacrylic acids. It is demonstrated that an increase of 11% of the content of syndiotactic triads compared to an atactic structure, does not modify the liquid c rystal behavior of homopolymers. Indeed, smectic OB, A, E and nematic phases were identified as for similar atactic samples. On the other ha nd, with both copolymers, the liquid crystalline behavior disappears t o the advantage of crystalline phases independently on the backbone co nfiguration. The results confirm that mesogenic interactions govern th e structural behavior of such polymethacrylate polymers. (C) 1998 Else vier Science Ltd. All rights reserved.