Genipin is an ideal crosslinking agent in biomedical applications, which can undergo ring-opening polymerization in alkaline condition. The polygenipin can create short-range and long-range intermolecular crosslinking between protein chains. In this paper, the polygenipin with different degree of polymerization was successfully prepared and used to fix gelatin composite materials. The short-range and long-range crosslinking effects of polygenipin were systematically studied. The results show that the composite materials present porous structure with tunable pore sizes in the gel state, which can be easily controlled by adjusting the degree of polymerization of polygenipin. Long-range crosslinking can increase the pore size of the gel. However, during the drying process, the composite films crosslinked by polygenipin with higher degree of polymerization shrank to smaller size to create more compact structure, resulting in the improvement of water resistance properties, thermal stability, tensile strength and darker color for the composite films. It is interesting that the composite films can partly swell to the original gel structure when in contact with water and saturated water vapor. All the composite films have excellent barrier properties against UV light.
