Studies on Drying and Swelling of PAAm-NIPA Composites in Various Compositions

Abstract

The steady-state fluorescence technique was introduced for studying the drying and swelling of disc-shaped PAAm-NIPA composites. Disc-shaped gels were formed with various acrylamides (AAm) and N-isopropylacrylamides (NIPA) by free radical crosslinking copolymerization in water. Composites were prepared with pyranine (Py) doped as a fluorescence probe. Scattered light I(sc) and fluorescence intensities I were monitored during drying of these gels. The fluorescence intensity of pyranine increased and decreased as drying and swelling time increased respectively for all samples. The Stern-Volmer equation combined with moving boundary and Li-Tanaka models were used to explain the behavior of I during drying and swelling respectively. It was found that the desorption coefficient D increased as NIPA contents were increased for a given temperature during drying. However the cooperative diffusion coefficient D(0) increased as NIPA contents were decreased during swelling at a given temperature. Supporting gravimetrical and volumetric experiments were also carried out during drying and swelling of PAAm-NIPA composites. It was observed that NIPA contents affect the drying and swelling process. POLYM. COMPOS. 32:928-936 2011. (C) 2011 Society of Plastics Engineers