High strength hydrogel using phenolated lignin

Abstract

Abstract In this investigation, lignin was phenolated and lignin based PVA hydrogels was synthesized. The highest yield in phenolation was found to be 123% at 10% sulfuric acid charge and L/P ratio of 1/4 at 120°C. FTIR spectra showing the increasing intensity of the bending vibration of phenolic hydroxyl group (O–H) at 1356 cm− 1 indicated the successful phenolation of lignin. A remarkable difference was observed in hydrogel preparation between phenolated (PhL) and nonphenolated lignin (L). Phenolated lignin had 98% yield while nonphenolated lignin yielded 88% at 1:1 L/PVA ratio. At L/PVA ratio of 2:1, nonphenolated lignin did not form stable hydrogel and remained very soft galley like liquid after 24 h of reaction. However, phenolated lignin formed stable hydrogel up to 5:1 L/PVA ratio with 78% yield. L/PVA hydrogel had higher swelling ratio in comparison with PhL/PVA hydrogel. At the lignin to PVA ratio of 1:2, the swelling ratio was 3101% and 4417% for phenolated and nonphenolated lignin hydrogels.