Preparation of surface-anionized poly(vinyl alcohol-co-methacrylic acid) hydrogel beads

Abstract

For the purpose of obtaining surface-anionized poly(vinyl alcohol) (PVA) hydrogel beads, vinyl acetate(VAc) and methacrylic acid(MAA) were copolymerized by the suspension polymerization technique and followed by the saponification. It was confirmed by H-1-NMR that the copolymerized microspheres contained carboxylic acid groups in their surface. poly(VAc-co-MAA) microspheres were completely saponified in the heterogeneous system. The saponification reaction was faster than that of PVAc microspheres. We observed the swelling property of saponified PVA microspheres treated in the acidic solution and in the alkaline solution successively. Saponified microspheres shrank in acidic solution and swelled in alkaline solution respectively, which was reversible. From the result, saponified microspheres were highly water-absorbing hydrogel beads and were certified -COOH group at their surface by H-1-NMR and FT-IR.