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Here we report the surface modification of chitosan (CS) microporous membrane via thermally induced graft copolymerization with acrylic Acid (AA)/N-isopropyl acrylamide (NIPAAm) in supercritical carbon dioxide (scCO2) at pressures ranging from 13 to 25 MPa utilizing benzyl peroxide as a free radical initiator.The effects of reaction pressure, initiator concentration, monomer concentration, reaction temperature, and reaction time on grafting yield (GY) were investigated.GY initially increases and then decreases with increasing polymerization temperature and AA and BPO concentrations.The optimum grafting conditions to obtain maximum GY are as follows: 8 h reaction time, 80 ℃ reaction temperature, 3.05× 10-2 g/mL AA concentration, 3× 10-3 g/mL BPO concentration,and 16 MPa reaction pressure.The double stimuli-responsive properties of grafted membranes were measured by water flux measurement.The water flux of the grafted CS membranes decreases with pH values from 2 to 7, even at considerably low GY (0.95 wt.%).And the water flux increases of CS membrane increases with the temperature.A novel and green modification method was developed to prepare biopolymer-based membranes.