Green robust pH–temperature-sensitive maleated poly(vinyl alcohol)-g-gelatin for encapsulated capsaicin

To date, smart hydrogels are widely used in the biomedical field such as wound dressings, artificial tendons, drugs and tissues owing to its sensitivity on environmental medium. The present work was focused on the preparation of a maleated poly(vinyl alcohol) (PVAM)-g-gelatin (GT) (PVAM-g-GT) from the PVAM and the GT in aqueous solutions using K₂S₂O₈ as an initiator. The characteristic bands of the novel smart PVAM-g-GT hydrogel were observed with peaks at 3288, 1541 and 1238 cm⁻¹ observed by FTIR. The increasing amounts of GT resulted in a decrease of the crystallinity. The swelling ratio in the water increased and the contact angle decreased with an increase of GT in the graft copolymer due to an increase of the hydrophilic groups in the hydrogel. In addition, the tensile strength of the novel smart PVAM-g-GT increased with an increase of the GT. The highest tensile strength and elongation at break were found at 8:2 PVAM:GT. Moreover, PVAM-g-GT shows a good responsibility to pH and temperature and it was used to a polymer matrix for encapsulation of capsaicin. A lower capsaicin release rate from the PVAM-g-GT hydrogel was obtained when immersed at pH 8 than at pH 2 due to hydrogen bond between the capsaicin and the polymer matrix.