The role of urethane acrylate in improving the elasticity of nano chitosan UV-curable hydrogel nanocomposite

In recent years, hydrogels based on acrylic acid and acrylamide have been widely used for easy polymerization and biocompatibility. On the other hand, due to energy saving and high reaction speed, curing systems with ultraviolet radiation have been expanded, which are considered in this study for synthesizing hydrogels and the flexible agent of the hydrogel network. The strength and stability of hydrogels are among the problems that are considered in their construction, and the strength of the network against solvent absorption leads to their many uses. In this study, the use of urethane acrylate as a flexible network agent has been used in the construction of a UV-curable hydrogel. For this purpose, at first, urethane acrylate with polyethylene glycol, isophorone diisocyanate, and hydroxyethyl methacrylate was synthesized and, after characterization, used in the hydrogel structure. The hydrogels were synthesized using an equal ratio of acrylamide and acrylic acid, various percentages of nano-chitosan (3, 6, 9, and 11), photo-initiator, and water under ultraviolet radiation. The accuracy of the hydrogel chemical structure was confirmed by FTIR analysis. The swelling ability and fluidity behavior of prepared hydrogels were investigated by weight measurement test and rheometry. According to the rheological test results and swelling capability, the sample containing 6 % w/w nano-chitosan was selected as the optimum sample. Then, the effect of urethane acrylate with different amounts of 10, 20, and 30 % on the swelling ability and elasticity behavior of hydrogels was studied. The results showed that hydrogel containing 10 % by weight of urethane acrylate had a four-fold equilibrium swelling with preservation of the network's structure.