THERMOTROPIC LIQUID-CRYSTALLINE COMB-LIKE POLYMERS WITH POLYACRYLAMIDE MAIN-CHAIN .2. INFLUENCE OF THE NATURE OF THE SUBSTITUENTS OF THE BIPHENYL MESOGENIC CORE

Comb-like polymers with polyacrylamide main chains and three types of lipophilic biphenyl side chains have been synthesized and their thermo tropic behaviour has been determined. All the polymers exhibit two sme ctic mesophases as a function of temperature, but the nature of the sm ectic mesophases is governed by the nature of the substituent R of the biphenyl core. For R = H, the polymers exhibit a double layer, ordere d, tilted smectic S-I2 and a double layer, disordered, tilted smectic S-C2. For R = CN, the polymers exhibit a double layer, disordered, til ted smectic Sc, and a double layer, disordered, perpendicular smectic S-A2. For R = O-CH2CH(CH3)-C2H5, the polymers exhibit a double layer, ordered, tilted smectic S-F2 and a double layer, disordered, tilted sm ectic S-C2, these two structures being chiral when the substituent R i s chiral. Comparison of the thermotropic behaviour of the polyacrylami de polymers with that of polymers with the same mesogenic cores but di fferent main chains shows the high smectogenic power of the polyacryla mide skeleton.