Development of gating membranes that are sensitive to the concentration of ethanol

Using a plasma graft-filling polymerization technique, we have prepared gating membranes that are sensitive to the concentration of ethanol. Poly-n-isopropylacrylamide-co-acrylic acid (poly-NIPAM-co-AAc), poly-n-isopropylacrylamide-co-acrylamide (poly-NIPAM-co-AAm) and poly-n-isopropylacrylamide-co-n-isopropylmethacrylamide (poly-NIPAM-co-NIPMAM) were grafted onto porous polyethylene (PE) substrates, and their gating response to the ethanol concentration in the feed was investigated. A copolymer of NIPAM and NIPMAM-grafted porous polyethylene membranes prepared from a monomer solution that contained 60 mol% of NIPMAM exhibited large changes in flux (from almost 0 up to about 100 kg/(m2 h)) with around 8 wt% of ethanol in the feed. The membranes that we have developed would be applicable to ethanol production in a biomass fermentation process that uses a purification stage employing membranes, where, for efficient production, it is important to control the ethanol concentration at a desired level in the fermentation tank.