Cellulose acetate-based smart gating membrane with pH/thermal response for flux control

Abstract

Inspired by the stomatal opening and closing mechanism of plants, a cellulose acetate-based pH/thermal response smart gating membrane was designed through surface segregation mechanism by embedding stimulation-responsive poly(N- isopropylacrylaminde) (PNIPAM)/poly(acrylic acid) (PAAc) microgels in the membrane pore channels. The water flux of the optimized smart membrane (CAM1.5) is 0.420 L/m2·h at 20 ℃/pH= 11 and changes to 121 L/m2·h at 65 ℃/pH= 1 with the highest gating ratio of 174. Meanwhile, the membrane gating ratio can be further improved to 216 when citric acid is used as coagulation bath. The carboxyl group content in the PAAc side chain is decreased and the interaction between water and microgels is improved under acid environment, which promotes the surface segregation of microgel. In addition, there is significant increase in the wet strength owing to the covalent crosslinking of citric acid. A fluid control system was designed based on the tunable membrane pore structure. According to the change of temperature and pH of the reaction system, the membrane can be opened and closed independently to precisely control the flow of reactants. This smart membrane shows promising applications in micro/nano fluid valves and temperature/pH sensitive biochemical reactors.