Synthesis and degradation of biodegradable photo-cross-linked poly(α,β-malic acid)-based hydrogel

To create a new biodegradable hydrogel, 2-hydroxyethyl methacrylate (HEMA) was grafted on poly(α,β-malic acid) (PMA) and ultraviolet (UV) photo-cross-linked. PMA was synthesized by polycondensation of L-malic acid without catalyst. The effects of the polycondensation reaction time and temperature on the polymer properties were studied. Increased temperature (in the range 110-130°C) accelerated intramolecular dehydration and depolymerization side reactions, increasing the low molecular weight fraction. The intramolecular dehydration was more sensitive to temperature than to reaction time. The photo-cross-link was carried out in the presence of photoinitiator Irgacure 2959. The gel content increased with increasing polymer concentration. The water uptake of PMA-based hydrogel ranged from 170% to 480% as the HEMA content varied from 12 to 4 mol %, respectively. The degradation behavior of PMA-based hydrogel was investigated. The weight loss of hydrogel was closely related to the HEMA grafting content and polymer concentration. Hydrogel degradation was found to proceed simultaneously at the surface and in the bulk of the hydrogels.