Fluorescence technique for monitoring swelling of PAAm-kappa-carrageenan gel composites

Abstract

Steady-state fluorescence (SSF) technique was employed for studying swelling of polyacrylamide (PAAm) gels with various content of kappa- carrageenan. Disc shaped composite gels were prepared by free-radical cross/inking copolymerization of acrylamide (AAm) with various amounts of kappa-carrageenan (kappa C) using N N'- methylenebis (acrylamide) (BIS) as crosslinker in the presence of ammonium persulfate (APS) initiator. Pyranine was introduced as a fluorescence probe. Fluorescence intensity of pyranine was monitored during in situ swelling processes of composite gels. It was observed that fluorescence intensity values decreased as swelling is proceeded. The Li-Tanaka equation was used to determine the swelling time constants tau and cooperative diffusion coefficients D from intensity variations during the swelling processes. It was shown that tau decreased and D increased as the kappa C content in the composites are increased.