Influence of chemical nature of citric and malic acids on reaction time of the crosslinking of polyvinyl alcohol hydrogels

Abstract

This work studied the incorporation of organic acids as crosslinking agents and reaction time on the crosslinked properties of poly(alcohol vinyl) (PVOH) hydrogels. PVOH hydrogels crosslinked with citric and L-malic acids were prepared, and the effects of heat-treatment time, and temperature on their swelling and hygroscopic performances were investigated by kinetics of water uptake, gel fraction, thermal analysis and FTIR. Both the swelling and rate of water uptake of hydrogels decreased with increasing heat-treatment time. While the swelling decreased with heat-treatment time, the chemical crosslinking shown in FTIR increased. DSC results indicated adsorbed water in the uncrosslinked PVOH and hydrogels, and the absorbed water changed the melting point and glass transition temperature. TGA analysis showed that the incorporation of organic acids caused more thermal stability. Analysis revealed that the heat treatment time and the initial crosslinking time increased the concentration of ester groups with a corresponding decrease in hydroxyl groups.