Thermal Phase Transitions of IOTA Carrageenan in CaCl2 Solutions: A Fluorescence Study

The fluorescence technique was employed to study thermal phase transitions of iota (ι-) carrageenan (IC) in CaCl₂ solution. IC gels underwent coil to double helix (c-h) and double helix to dimer (h-d) transitions upon cooling. Upon heating IC gels presented dimer to double helix (d-h) and double helix to coil (h-c) transitions, showing hysteresis types of transition paths. Scattered light, I_sc and fluorescence intensity, I, were monitored against temperature to determine phase transitions. Transition temperatures were determined from the derivative of the transition paths. The critical gel fraction exponent, β, was measured and found to be in accord with the classic Flory–Stockmayer model.