Gamma radiation-induced synthesis of chitosan-graft-poly(vinyl acetate): structural elucidation and solvent-dependent grafting behavior

Abstract Traditionally, the grafting of vinyl acetate onto chitosan has relied on chemical initiators, such as redox or peroxide systems. Herein, we report for the first time the gamma radiation-induced graft polymerization of vinyl acetate onto chitosan, providing a clean, initiator-free, and controllable route for generating chitosan-graft-poly(vinyl acetate) copolymers. The central hypothesis is that gamma irradiation activates the reactive sites on chitosan, whose selectivity toward hydroxyl or amino groups is modulated by solvent polarity, thereby governing the structural and thermal behavior of the resulting copolymer. The reaction was carried out at 25 kGy in different solvents (ethanol, hexane, ethyl acetate, chloroform, acetone, and acetic acid), and the resulting products were characterized by Fourier transform infrared and solid-state Nuclear magnetic resonance cross-polarization magic angle spinning, confirming the successful grafting of short poly(vinyl acetate) chains onto the chitosan backbone. Thermogravimetric analysis and differential scanning calorimetry revealed solvent-dependent variations in the thermal stability and transition temperatures, indicating distinct polymeric architectures. Viability and scratch assays with human dermal fibroblasts demonstrated the high biocompatibility and enhanced cell proliferation of the copolymers synthesized in hexane or acetic acid. These findings establish gamma radiation as a versatile tool for tailoring chitosan functionalization through solvent-controlled radical mechanisms, thereby providing new opportunities for the rational design of biocompatible carbohydrate-based materials.