Research of Norbornene Functionalized Chitosan with Tailorable Degree of Substitution

Chitosan has attracted widespread attention in the medical industry because of its abundant yield, biocompatibility, biodegradability, antibacterial and anti-inflammatory properties. However, chitosan shows limited water solubility, preventing its development. To functionalize chitosan to water-soluble chitosanbased hydrogels, such as photo-curable hydrogels, which can be widely used in cell culture, tissue engineering, 3D printing and other fields. In the field of photocuring reactions, the thiol-norbornene click reaction is worth to be studied due to its extremely high reactivity. In this research, a family of norbornene-functionalized chitosan were prepared by changing the reaction parameters, including the amount of reactants, reaction time and pH of the system. A calculation method of degree of substitution was proposed, based on the characterization of 1H nuclear magnetic resonance spectroscopy. The research investigated that in this chitosan functionalized reaction system, the substitution reaction and the anhydride hydrolysis reaction occur simultaneously and intact, and and the two reactions affect each other The reaction rate and degree of substitution can be tailored by comprehensively adjusting the reaction parameters. The degree of substitution ranged from 9% to 43% in this research. Norbornene-functionalized chitosan was able to absorb water more than 50% in mass change, and its excellent water absorption ability can be used in the application areas of wound healing and drug delivery and other fields.