An eco-friendly synthesis of modified poly(vinyl alcohol)-graft-lactic acid by curing method

Abstract

Firstly, this research aimed to employ an eco-friendly synthesis method to prepare modified poly(vinyl alcohol)-graft-lactic acid (PVA-g-LA) thin hydrogel films with different mass ratio of PVA to LA, i.e., 5.0:2.5, 5.0:5.0, 5.0:7.5, and 5.0:10.0 g, respectively. They were mixed in aqueous solutions without initiator and catalyst and were cured by thermal annealing at 120 °C for 120, 150, or 180 min to create the ester bond between the carboxyl groups of LA and the hydroxyl groups of PVA backbone. The second aim was to characterize the thermal analysis, differential scanning calorimetry, and thermogravimetric analysis and to detect the main functional groups by Fourier transform infrared spectroscopy. The third aim was to study the swelling–deswelling behavior and moisture measurement per dry mass. The modified PVA-g-LA thin hydrogel films that the ranges of the glass transition temperature, melting temperature, and decomposition temperature were 78.7–115.0, 138.8–199.1, and 287.3–344.0 °C, respectively, with three regions for mass lost. The carbonyl group in modified PVA-g-LA thin hydrogel films appeared around at 1730–1758 cm−1. They showed good swelling in distilled water when thermally cured at 120 °C for 120 min and had different swelling–deswelling behavior. Moisture in the thin hydrogel films depended on curing time and mass ratio of PVA and LA due to ester interaction in their structure. In conclusion, eco-friendly synthesis of modified PVA-g-LA thin hydrogel films suitable for pharmaceutical and medical applications can be easily prepared.