SYNTHESIS OF HYDROGEL WITH NEEM GUM/ 3-APBA/PVA USING PBA-DIOL ESTER BOND

Abstract

Hydrogels are three-dimensional networks of hydrophilic polymers which can absorb large quantities of water and can retain the absorbed water without disintegrating. The present dissertation reports the synthesis of a neem gum/3-aminophenylboronic acid/polyvinyl alcohol (NG/3-APBA/PVA) hydrogel through PBA-diol ester bond formation. Neem gum was selected as a renewable natural polysaccharide, PVA was used as a hydroxyl-rich synthetic polymer, and 3-APBA was introduced as a boronic acid containing linker. Neem gum was first oxidized using hydrogen peroxide to produce oxidized neem gum (O-NG), followed by EDC/NHS-mediated grafting of 3-APBA through amide bond formation. The grafted polymer was then mixed with PVA under alkaline conditions to promote PBA-diol ester interactions, and freeze-thaw cycling was used to obtain stable hydrogel networks. The synthesized materials were characterized by FTIR spectroscopy, swelling analysis, rheology, syringeability testing, and self-healing evaluation. FTIR confirmed oxidation of neem gum, amide bond formation after 3 APBA grafting, and retention of boronic acid functionality in Hydrogel A and Hydrogel B. Hydrogel A showed higher swelling of approximately 93%, whereas Hydrogel B showed lower swelling of approximately 75%, indicating a denser network under higher alkaline conditions. Rheological results confirmed elastic solid-like behavior, shear-thinning viscosity, and successful hydrogel network formation. Both hydrogels were syringeable through a 16G needle, with Hydrogel A and Hydrogel B showing syringeability values of 81% and 79.9%, respectively. Partial self-healing after 24 hours further supported the dynamic nature of the PBA-diol ester network. Overall, the study demonstrates that neem gum can be chemically modified and combined with PVA to form a functional dynamic hydrogel system.