▎ 摘　　要

NOVELTY - Preparing environment friendly hydrogel, involves dissolving polyvinyl alcohol, four-arm polyethylene glycol and four-arm polyethylene glycol carboxylate in pure water. Then the mixture is placed in ice bath and stirred at 100-200rotatins per minute for 12-24 hours until uniform solution is obtained. Graphene oxide is added to the solution and stirred magnetically for 6-12 hours. Then the solution is placed in ice bath at 0 degrees C for 30-60 minutes under ultrasonic vibrations to disperse graphene oxide uniformly. The dispersion is transferred to mold and is frozen at -30 degrees C for 24 hours. USE - Method for preparing environment friendly hydrogel (claimed). It can be used in biomedical and tissue engineering. ADVANTAGE - The method enables preparation of environment friendly hydrogel which has excellent mechanical strength and self-healing features. The method is simple. DETAILED DESCRIPTION - Preparing environment friendly hydrogel, involves dissolving polyvinyl alcohol, four-arm polyethylene glycol and four-arm polyethylene glycol carboxylate in pure water. Then the mixture is placed in ice bath and stirred at 100-200rotatins per minute for 12-24 hours until uniform solution is obtained. Graphene oxide is added to the solution and stirred magnetically for 6-12 hours. Then the solution is placed in ice bath at 0 degrees C for 30-60 minutes under ultrasonic vibrations to disperse graphene oxide uniformly. The dispersion is transferred to mold and is frozen at -30 degrees C for 24 hours then taken out at 20 degrees C. The freeze-thawing process is repeated 5 times and washed with pure water a number of times to form gel A. Where polyvinyl alcohol is 10-15% of solution, four-arm polyethylene glycol is 2-5% of solution, four-arm polyethylene glycol carboxylate is 2-4% of solution and graphene oxide is 0.5-2% of solution. Acrylic acid (AAc), acrylamide (AAm), cross-linking agent N,N'-methylene-bis-acrylamide (BIS) and aqueous solution of photo-initiator are added and stirred at 300-600rotatins per minute. The resulting solution is poured into mold having gel A and sealed and soaked for 24-48 hours until gel is fully swollen. Black cloth is wrapped to avoid light. The swollen gel is placed in ultraviolet light at predetermined distance from source. After 18-24 hours gel B is obtained. Where acrylic acid concentration is 4-8%, acrylamide concentration is 8-12%, bis-acrylamide cross-linking agent is 4-10% of acrylic acid and acrylamide concentration and photoinitiator is 1-3% of acrylic acid and acrylamide concentration. The gel B is washed a number of times and is placed into the container in water bath at 60-90 degrees C for 8-12 hours to obtain the final product.