Synthesis, characterization, and swelling behaviors of chitosan-g-poly(acrylic acid)/poly(vinyl alcohol) semi-IPN superabsorbent hydrogels

A series of granulated semi-interpenetrating polymer network (semi-IPN) superabsorbent hydrogels composed of chitosan-g-poly(acrylic acid) (CTS-g-PAA) and poly(vinyl alcohol) (PVA) were prepared by solution polymerization using ammonium persulfate (APS) as an initiator and N,N(-methylenebisacrylamide (MBA) as a crosslinker. The effects of reaction conditions such as the concentration of MBA, the weight ratio of AA to CTS, and the content of PVA on water absorbency were investigated. Infrared (IR) spectra and differential scanning calorimetry (DSC) analyses confirmed that AA had been grafted onto CTS backbone, and PVA semi-interpenetrating into CTS-g-PAA networks. SEM analyses indicated that CTS-g-PAA/PVA has improved porous surface and PVA was uniformly dispersed in CTS-gPAA network. The semi-IPN hydrogel containing 10wt% PVA shows the highest water absorbency of 353 and 53gg S1 in distilled water and 0.9wt% NaCl solution, respectively. Swelling behaviors revealed that the introduction of PVA could improve the swelling rate and enhance the pH stability of the superabsorbent hydrogel. Copyright 2009 John Wiley & Sons, Ltd.