Abstract: In order to improve the efficiency of grafting vinyl monomers on the surface of silk fibroin and produce fibroin-based water-absorbing composite, the graft reaction of acrylic acid (AA) and silk fibroin (SF) was first carried out in this work by means of EDC (1-(3-dimethylamino) propyl) carbodiimide hydrochloride-3-ethyl)/NHS (N-hydroxy succinimide) crosslinking system. The carboxyl groups were reacted with amino groups on SF, which could introduce double bonds into fibroin proteins to increase the reactive sites of graft copolymerization. And then copolymerization of SF, AA, acrylamide (AM) and cross linker of N, N-methylene-bis-acrylamide (MBA) was catalyzed using horseradish peroxidase (HRP) system, and finally water-absorbing material of regenerated silk fibroin was fabricated. Changes in the content of free amino groups in silk fibroin solution via multiple methods and AA in the solution before and after the graft reaction, shapes of prepared fibroin membranes under different conditions were evaluated, respectively. The water absorption and conservation performance, repeat water-absorbing and releasing properties were also investigated. The results indicated that AA monomer was successfully grafted onto SF via EDC/NHS, and the water-absorbing composite of grafted SF copolymerized with AA and AM had better water absorption, water retention and repeat absorbency compared with ungrafted SF. Meanwhile, fast packet load capacity and preferable thermal stability were achieved.

Key words: silk fibroin (SF), acrylic acid (AA), EDC/NHS, horseradish peroxidase (HRP), water-absorbing material