Universality of sol--gel phase transition ofκ-carrageenan in various salts: a steady state fluorescence study

Thermal phase transitions of κ-carrageenan in NaCl, KCl and CaCl2 solutions were studied using steady state fluorescence (SSF) technique. Pyranine was introduced as a fluorescence probe for studying sol--gel phase transitions. Scattered light, I sc and fluorescence intensity, I was monitored against temperature to determine the sol--gel (T sg) phase transition temperatures. It was observed that T sg values are strongly correlated to NaCl, KCl and CaCl2 contents. The weight average degree of polymerization, DP w and gel fraction G, exponents (γ and β) were measured and found to be in accord with the classical Flory--Stockmayer model, i.e., γ and β were found to be close to 1.0, independent of salt content.