ALGINIC ACID GELS - THE EFFECT OF ALGINATE CHEMICAL-COMPOSITION AND MOLECULAR-WEIGHT

The effect of chemical composition and sequence and molecular weight o f different alginate samples on the final properties of alginic acid g els have been studied. It is shown that alginates with a high content of guluronic acid blocks give gels of a considerably higher strength c ompared to alginates rich in mannuronate. A high fraction of homopolym eric blocks seems to favour the formation of junction zones. Compared to Ca-alginate gels, a more extended molecular weight dependent regime is observed. Kinetic measurements show an initially rapid (similar to 30 min) sol-gel transition with an apparent equilibrium in the dynami c storage moduli gradually obtained within 24-48 h, depending on the c hemical composition of the alginate sample used. Mechanical spectrosco py reveals gels with a high degree of solid-like nature, with an incre asing frequency dependence with decreasing molecular weight.