화학공학소재연구정보센터
Macromolecules, Vol.42, No.13, 4775-4786, 2009
Liquid Crystallinity and Other Properties in Complexes of Cationic Azo-Containing Surfactomesogens with Poly(styrenesulfonate)
A series of stoichiometric ionically bonded side-chain polymer complexes, constructed from poly(styrenesulfonate) (PSS) and quaternary ammonium-functionalized azo-containing surfactomesogens (SMs) with hexyl and decyl spacers, were prepared under rigorous conditions and thoroughly dried, and their potential thermotropic liquid crystal (LC) properties were investigated. The SM series consists of eight differently substituted azobenzene cores with a range of polarities. In their Br-neutralized form, they,ire generally crystalline to high temperatures (those with an ethylamine linking group having very slow recrystallization kinetics). Only some of the complexes showed LC properties in unannealed form, while several others required exceedingly long annealing times at appropriate temperatures to reveal LC character, attributed to the semirigid PS backbone, relatively high molecular weight, and strong ionic interactions that greatly retard the kinetics of chain reorganization toward equilibrium. Among the decyl-spacer complexes, only the two with an ethylamine linking group appear intrinsically isotropic, whereas, among the hexyl-spacer complexes, just two revealed LC character. X-ray diffraction (XRD) indicated that the I-C structure is generally of an effectively single-layer SmA type, but while the complexes based oil SMs with nonpolar tails produce a classical SmA XRD pattern, those with polar tails produce one with a quasi-extinct or reduced intensity first-order diffraction peak. The former also have lamellar thicknesses that areca. 5 angstrom less than the latter, in agreement with literature data for all-covalent. polystyrene-based analogues and explained by greater mesogen interdigitation for those with nonpolar tails that thus lie in the alkyl spacer subplane. A model proposed to rationalize the apparent extinction of the first-order XRD peak relics oil dipole-dipole interactions between the polar mesogens and the ion pairs that allow them to share the same subplane, thus halving the effective lamellar thickness. A Study of photoinduced birefringence (PIB) in selected complexes, compared with a spacer-free complex, shows that the flexible spacer plays a significant role in reducing PIB stability.