Synthesis and characterization of chitosan/polyvinyl alcohol crosslinked poly(N-isopropylacrylamide) smart hydrogels via γ-radiation

Chitosan-based smart hydrogels with stable mechanics and good flexibility have many desirable qualities and broad applications. In this study, novel smart hydrogels of chitosan crosslinked with poly(N-Isopropylacrylamide) (pNIPAAm) and polyvinyl alcohol (PVA) were synthesized through freezing and thawing procedures followed by gamma (γ)-radiation at room temperature. The effect of γ-irradiation dose on the gel fraction and water absorption characteristics of chitosan-pNIPAAm hydrogels was investigated. In addition, the structure–property behaviour of the hydrogels was characterized using Fourier Transform Infra-Red (FTIR) spectroscopy and thermogravimetric analysis (TGA). The experimental results revealed that the hydrogels synthesized with a 15-kGy total dose showed a higher gel content (83.73%) compared to 5-kGy and 10-kGy total doses, while the appropriate dose of γ-radiation to achieve the highest absorption in water (484.146%) was 5-kGy. The hydrogel characterization test confirmed that cross-linking occurred between pNIPAAm, PVA, and chitosan. A higher the radiation dose resulted in more cross-links in the hydrogel and resulted in better thermal stability. This study confirmed that chitosan/PVA cross-linked pNIPAAm hydrogel with dual pH/temperature stimuli-responsiveness holds promise for various applications.