Gamma rays-induced 2-hydroxyethyl methacrylate graft copolymerization on methylcellulose-based films: Structure analysis and physicochemical properties

The effect of 2-hydroxyethyl methacrylate (HEMA) grafting on the structure and physicochemical properties of methylcellulose (MC)-based films was investigated by using gamma (γ) radiation. HEMA (0.1-1%, w/w) was incorporated into MC-based aqueous formulation containing 1% MC, 0.5% vegetable oil, 0.25% glycerol and 0.025% Tween®80. Films were obtained by casting and then exposed to γ-radiation (5-25 kGy). Results revealed that films containing 1% HEMA showed the highest puncture strength (PS) values (282 N/mm) at 10 kGy. Measurements of water vapor permeability (WVP) demonstrated that films exposed to high radiation doses (25 kGy) generated highest barrier properties (5.5 g mm/m2 day kPa) due to a possible grafted complex MC-HEMA. Fourier transform infrared (FTIR) analysis showed a decrease of the vinyl vibration band from HEMA at 1636 cm−1 after grafting, suggesting that graft polymerization occurred via a HEMA reaction from vinylidene into methylene group, combined with HEMA homopolymerization. Moreover, FTIR peaks clearly indicated that MC-g-HEMA copolymer grafting was improved with higher radiation doses (0-100 kGy). Scanning electron microscopy (SEM) of MC-g-HEMA films suggested an enhanced smoother appearance. Therefore, these results allowed confirming that polyHEMA grafting into MC polymer was carried out successfully by using γ-radiation.