An X‐ray investigation of terminally carboxyl oligo (ethylene oxide) monomethyl ethers‐substituted side‐chain liquid crystalline polysiloxanes

Abstract

Abstract4′‐[Oligo(ethylene oxide) monomethyl ether carbonyl] biphenyl‐4‐yl 4‐(alkenyloxy) benzoate side‐chain liquid crystalline (LC) polysiloxane polymers with various lengths of a terminal group and spacer were prepared. The mesophase structure and transition temperature of those polymers were investigated using methods of X‐ray diffraction, polarized optical microscopy, and differential scanning calorimetry, respectively. The mesophases of the polymers were smectic ones. The layer spacing d1s and the side‐chain distance of d2s obtained were around 29–34 Å and 4.4–4.6 Å, respectively. d1s were much shorter than twice the lengths of the side chains presumed in the fully extended conformation. Hence, the two‐layer end‐on packings or the packing with overlapping of tails model seemed not able to interpret the mesophase structure of those polymers studied. The effects of temperature on the mesophase microstructure of 4′‐[ethylene oxide monomethyl ether carbonyl] biphenyl‐4‐yl 4‐(pentenyloxy) benzoate side‐chain LC polysiloxane polymer were also studied using the X‐ray diffraction method. It was found that both d1 and d2 of the polymer in the mesophase temperature range became shorter with decreasing temperature and the long‐and short‐range order could remain, to some extent, at temperatures above the isotropic transition temperature and temperatures below the melting temperature. © 1993 John Wiley & Sons, Inc.