SO2 Initiated polymerization of Acrylamide and studies on hydrogels based on resulting Polyacrylamide

摘要

The polymerization of AM was carried out under the different concentration of acrylamide and cross linkers in an aqueous solution of SO2 gas as initiator at 50°c. The resulting polyacrylamide was saponified with NaOH solution. The hydrolysed polymers show high degree of water swelling (>500) than that of unhydrolysed polymers (<50). Swellability of the gel decreases with the increasing concentration of N, N'- methylene bisacrylamide - a cross linker which enhances the degree of cross linking in the polymer chains. The increased cross linking restrict the expansion of polymer network which causes the lowering of the water absorbency. It was observed that polymer hydration increases with the molar mass of polyacrylamide. The swellability of polyacrylamide hydrogels is greatly lowered by the addition of ionic salts in the swelling medium. Both ionic strength and valency of the salts are responsible to decrease the water up taking capacity of the gels which remain unaffected by non dessociating nature of Urea. The hydrogels, so prepared, are stable and quite able to undergo swelling- deswelling cycles suggesting their reversible characters. Results are similar to those obtained for polyacrylamide formed during the course of NO 2 initiation in H2O.