Swelling Kinetics of PAAm-kappa-Carrageenan Composites: A Fluorescence Technique
The steady-state fluorescence (SSF) technique was introduced for studying swelling of disc-shaped polyacrylamide (PAAm) gels containing various amount of kappa-carrageenan (kappa C). They were prepared by free-radical cross-linking copolymerization. N N'-methylenebisacrylamide (BIS) and ammonium persulfate (APS) were added as a crosslinker and an initiator respectively. Composite gels were prepared at 80 degrees C with pyranine as a fluorescence probe. After drying of these gels swelling kinetics were performed in water at 60 degrees C by real-time monitoring of the pyranine fluorescence intensity I which decreased as swelling proceeded. 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 gels during the swelling processes in all cases. It was observed that tau(1) decreased and D(0) increased as the kappa C concentrations in the composites were increased indicating that high kappa C gels swell faster than low kappa C gels.