HYDROGEN-BONDING-MEDIATED GENERATION OF SIDE-CHAIN LIQUID-CRYSTALLINEPOLYMERS FROM COMPLEMENTARY NONMESOGENIC PRECURSORS

Liquid crystalline phases in macromolecular assemblies have been gener ated by utilizing complementary hydrogen-bonding interaction between f unctional vinyl polymers and rigid aromatic derivatives. While neither of the individual components is mesogenic, the resulting assemblies e xhibited liquid crystalline behavior. Poly((2-dimethylamino)ethyl meth acrylate) and poly(a-hydroxyethyl methacrylate) were chosen as the fun ctional polymer backbone bearing proton-accepting and proton-donating groups, respectively. As rigid aromatic units, 4-hydroxybiphenyl, tran s-4-hydroxystilbene, 4'-methoxy-4-hydroxyazobenzene, and 4-pyridylbenz oate were used. All the polymeric assemblies were obtained as transpar ent films and they exhibited liquid crystalline properties. Hydrogen-b onding in these assemblies was evident from their FTIR and C-13 NMR sp ectra. The liquid crystalline behavior of these hydrogen-bonded polyme ric assemblies was established by DSC, polarizing microscopy, and X-ra y diffractometry. Phase diagrams of the mixtures revealed the dependen ce of the liquid crystalline transitions on the composition of such bi nary mixtures. Generation of liquid crysalline phases in these hydroge n-bonded polymeric assemblies derived from non-liquid crystalline prec ursors without the mediation of a flexible spacer is unprecedented. Fu rthermore, this approach offers a relatively simple route to prepare f unctional materials with controlled molecular architecture from readil y accessible and simpler precursors.