▎ 摘　　要

NOVELTY - Preparation of hydrogel involves dispersing graphene oxide in anhydrous dichloromethane, adding 4-dimethylaminopyridine and bromophenylacetic acid, dissolving N,N'-dicyclohexylcarbodiimide in dichloromethane and dripping into the obtained solution, maintaining for 1-72 hours to obtain a bromine-graphene oxide, adding N-isopropylacrylamide, ascorbic acid, copper bromide, pentamethyldiethylenetriamine, ethyl 2-bromoisobutyrate and isopropanol (or dimethylformamide), reacting, maintaining for 1-72 hours to obtain an N-isopropylacrylamide-graphene oxide, performing pickering emulsification using N-isopropylacrylamide-graphene oxide, deionized water and toluene, grafting with polydopamine using tris hydrochloride buffer to obtain an N-isopropylacrylamide-graphene oxide-polydopamine Janus nanosheets, adding the nanosheets, acrylic acid, distilled water, free radical initiator, preferably potassium persulfate, acryloyl- beta -cyclodextrin and ferric chloride hexahydrate, and reacting. USE - Preparation of hydrogel used for desalinating seawater. ADVANTAGE - The method enables preparation of hydrogel having desired temperature sensitivity, photothermal effect, self-repairing property, swelling property, water absorption property, and mechanical strength. The hydrogel enables efficient desalination of seawater. DETAILED DESCRIPTION - Preparation of hydrogel involves dispersing (i) graphene oxide in anhydrous dichloromethane, adding 4-dimethylaminopyridine and bromophenylacetic acid, stirring, dissolving N,N'-dicyclohexylcarbodiimide in dichloromethane under ice-bath condition of -10 degrees C to 20 degrees C and dripping into the obtained solution, increasing the reaction temperature to a temperature of 5-50 degrees C, maintaining for 1-72 hours to obtain a bromine-graphene oxide, in which the mass ratio of graphene oxide, 4-dimethylaminopyridinem bromophenylacetic acid, N,N'-dicyclohexylcarbodiimide and dichloromethane is 1-100:0.01-10:1-1000:1-1000:1-1000, adding bromine-graphene oxide, N-isopropylacrylamide, ascorbic acid, copper bromide, pentamethyldiethylenetriamine, ethyl 2-bromoisobutyrate and isopropanol (or dimethylformamide) to a flask, reacting at 10-200 degrees C under a nitrogen atmosphere, in which the ratio of graphene oxide, N-isopropylacrylamide and isopropanol (or dimethylformamide) is 1-100:0.5-500:1-1000, and the molar ratio of ascorbic acid, copper bromide, pentamethyldiethylenetriamine and ethyl 2-bromoisobutyrate is 1-100:0.1-100:0.1-100:0.1-100, maintaining for 1-72 hours to obtain an N-isopropylacrylamide-graphene oxide, performing pickering emulsification using N-isopropylacrylamide-graphene oxide as an oil phase, deionized water as an aqueous phase, and toluene at 10-150 degrees C for 1-48 hours, in which the volume ratio of toluene with respect to deionized water is 0.1-100:1-100, grafting with polydopamine using tris hydrochloride buffer (pH = 7.5-10) at 10-100 degrees C for 1-36 hours, in which the ratio of polydopamine, tris hydrochloride buffer and N-isopropylacrylamide-graphene oxide is 1-100:1-100:10-1000 to obtain an N-isopropylacrylamide-graphene oxide-polydopamine Janus nanosheets having temperature sensitivity and photothermal effect, adding (ii) the N-isopropylacrylamide-graphene oxide-polydopamine Janus nanosheets, acrylic acid, distilled water, free radical initiator, preferably potassium persulfate, acryloyl- beta -cyclodextrin and ferric chloride hexahydrate, reacting at 10-100 degrees C for 0.5-24 hours to obtain a self-repairing hydrogel, in which the mass ratio of acrylic acid, distilled water, acryloyl- beta -cyclodextrin, ferric chloride hexahydrate, free radical initiator and N-isopropylacrylamide-graphene oxide-polydopamine Janus nanosheets of 1-100:1-100:1-100:0.1-100:1-100:1-1000, and desalinating (iii) seawater by placing the hydrogel in a container filled with seawater, soaking the hydrogel for 0.5-240 hours, taking out the hydrogel, measuring the mass of the hydrogel, placing the hydrogel under a light source having a wavelength of 200-5000 nm for specific time period, recording the mass of the hydrogel at regular intervals of 1-60 minutes at 5-35 degrees C to calculate evaporation rate of the seawater.