Two types of temperature induced transitions of poly(I) · poly(C) liquid crystals

Abstract

Small-angle X-ray scattering curves, CD. spectra and textures of the liquid-crystalline phase formed from poly(I) · poly(C) in water-salt solutions containing poly(ethyleneglycol) have been obtained at different temperatures. It was found that heating the poly(I) · poly(C) liquid-crystalline phase is accompanied by two types of transitions, the first being cholesteric → compensated structure → cholesteric and the second being cholesteric → isotropic state transition. The latter transition takes place at a temperature which corresponds to that of separation of chains of a double-stranded poly(I) · poly(C) molecule. The temperature dependence of the abnormally high optical activity of poly(I) · poly(C) liquid crystals allows us to estimate the order parameter of poly(I) · poly(C) molecules in both the liquid-crystalline phase and the liquid-crystalline microphases.