Gelation processes in the non-stoichiometric polylectrolyte-surfactant complex between κ-carrageenan and dodecyltrimethylammonium chloride in KCl

The gelation processes taking place in the non-stoichiometric complex between κ-carrageenan and dodecyltrimethylammonium chloride in KCl were studied. The mechanical properties of the hydrogels show a gradual reinforcement when the amount of surfactant in the complex increases, indicative of a more densely cross-linked polymer network. The thermal and viscoelastic behavior of complexes during cooling is similar to that of κ-carrageenan alone. Nevertheless, the melting of the gel splits into two endothermic processes. The emergence of a new transition during heating indicates that the overall polymer network is related to two types of networks: one formed by typical bonds between κ-carrageenan macromolecular chains and the other associated to hydrophobic blocks developing as a consequence of the cooperative nature of polyelectrolyte-surfactant interactions. In the hydrogel these two networks co-exist, probably semi-interpenetrated, somehow interconnected at the molecular level.