Characterization of strong polyelectrolyte hydrogels based on poly(vinyl alcohol)

Maleic anhydride (MA) was grafted onto both partially and fully hydrolyzed poly(vinyl alcohol) (PVA) in the presence of an initiator. Strong polyelectrolyte polymers were prepared by sulfonation of PVA-MA grafts. The sulfonation was completed by reaction of hydroxyl groups of PVA-MA grafts with two different sulfonating reagents (chlorosulfonic acid and pyridine sulfonic acid). The sulfonation degree was evaluated by acid-base titration and H-1 NMR analysis. The solution behaviour of the prepared grafts was evaluated from viscosity measurements. Four kinds of water-insoluble PVA-MA and PVA-MA-SO3H hydrogels were prepared by heat treatment, physical gelation and chemical crosslinking with different weight ratios of N,N-methylene bisacrylamide (MBA) crosslinker. The swelling parameters were measured for all prepared gels in deionized water and aqueous solutions at different pH values from 2 to 12 having constant ionic strength (I = 0.1). All gels exhibit a different swelling behaviour upon environmental pH changes. (C) 2004 Society of Chemical Industry.