Thermodynamic stability of the ordered conformations of carrageenan polyelectrolytes

Manning's counterion condensation theory has been applied to the temperature‐induced conformational transition of κ‐ and ι‐carrageenan in the solution and gel states. The formalism of the theory has been extended to transitions between conformations with charge densities below or across the counterion condensation threshold. Measurements of the dependence of the melting temperature on ionic strength, and of the enthalpy of melting, are interpreted with the theory as indicating that the conformational transition is intramolecular and that side‐by‐side dimerization of chains gives rise to the gel structure.