Thermotropic comb-like polymers: 3. Comparative behaviour of acrylamide and methacrylamide polymers with undecanoylbiphenyl side chains

Abstract

Methacrylamidoundecanoylbiphenyl monomer was synthesized from 11-aminoundecanoic acid, and X-ray diffraction showed that it exhibits only crystalline structures. Its radical polymerization, followed by n.m.r. and g.p.c., provided comb-like polymers and their macromolecular characteristics were determined. Their thermotropic behaviour was studied by X-ray diffraction and the X-ray information showed that they exhibit, as a function of temperature, an ordered, perpendicular, monolayer, smectic SB1 phase and a disordered, perpendicular, monolayer, smectic SA1 phase. Comparison with polyacrylamide polymers with the same side chains showed that, if the two types of polymers exhibit two smectic phases (an ordered and a disordered,one), as a function of temperature, the nature of the main chains determines the types of smectic structures of the polymers. Polyacrylamide polymers exhibit two tilted bilayer smectic mesophases: S12 and SC2, instead of the two perpendicular monolayer smectic phases SB1 and SA1 exhibited by polymethacrylamide polymers. © 1997 Elsevier Science Ltd.