A NOVEL CHIRAL NEMATIC PHASE IN AQUEOUS KAPPA-CARRAGEENAN

A novel liquid crystalline phase has been identified in the kappa-carr ageenan/NaI/water system. Solutions of ultrasonically degraded carrage enan were prepared in 0.1 III NaI both by direct mixing and by osmotic compression, and a macroscopic phase separation into one anisotropic bottom phase and one isotropic top phase was found in the concentratio n range 5-11% (w/w). The properties of the anisotropic phase were inve stigated by small-angle X-ray scattering (SAXS), Na-23 NMR, and polari zed light microscopy. The phase could be melted to a completely isotro pic solution by heating to 65 degrees C, and the anisotropic phase slo wly re-formed again on standing at room temperature, indicating that t he phase is in thermodynamic equilibrium. Intact(nondegraded) kappa-ca rrageenan failed to give macroscopic phase separation but yielded inst ead birefringent gels for concentrations higher than 2%.