Temperature effect on the swelling of PAAm-kappa-carrageenan composites

Abstract

The steady-state fluorescence (SSF) technique was used for studying swelling of disc-shaped polyacrylamide (PAAm)-kappa-carrageenan (kappa C) composites which were prepared by free-radical crosslinking copolymerization at 80 degrees C. Pyranine was introduced as a fluorescence probe during polymerization. Swelling experiments were performed in water at various temperatures by real-time monitoring of the pyranine (Py) fluorescence intensity I which decreased as swelling proceeded. Stern-Volmer equation is modified for low quenching efficiencies to interpret the behavior of Py intensity during the swelling of PAAm-kappa C composites. The Li-Tanaka equation was used to determine the swelling time constants tau(1) and cooperative diffusion coefficients D(0) from fluorescence intensity weight and volume variations of the composites at various temperatures. It was observed that tau(1) first decreased up to 40 degrees C and then increased

naturally D0 increased up to 40 degrees C and then decrease for all kappa C content gels. Swelling activation energies DE were measured for the swelling composites which are found to be exothermic and endothermic in between 30-40 and 40-60 degrees C respectively. (C) 2011 Wiley Periodicals Inc. J Appl Polym Sci 123: 1746-1754 2012