Liquid-crystalline hydrogels. 1. Enhanced effects of incorporation of acrylic acid units on the liquid-crystalline ordering

Copolymers composed of 11-(4'-cyanobiphenyloxy)undecyl acrylate (11CBA) and acrylic acid (AA), poly(11CBA-co-AA)s, were prepared by changing their mol ar ratio, and their structures were investigated under various temperatures . From wide- and small-angle X-ray studies, it was found that poly(11CBA) a nd poly(11CBA-co-AA)s with a mole fraction of 11CBA more than 0.26 showed t he smectic A (SmA) phase with a layer spacing (d(2)) of 46-58 Angstrom, to which the mesogenic moiety of 11CBA attached perpendicularly with a side-by -side spacing of 4.3 Angstrom (d(1)). The ordering as well as the d(2) spac ing of the smectic layer increased by incorporating an appropriate amount o f AA. At the same time, the isotropic temperature of the copolymer increase d with AA content. The enhanced ordering and the thermostability by introdu cing AA were explained in terms of the cooperative hydrogen interaction bet ween the carboxylic groups of AA.