PREPARATION OF TEMPERATURE-SENSITIVE MEMBRANES BY GRAFT-POLYMERIZATION ONTO A POROUS MEMBRANE

Temperature-sensitive membranes were prepared by grafting of poly(N-isopropylacrylamide) (polyIPAAm) and its copolymers onto a porous poly(vinylidene fluoride) membrane. Poly-IPAAm is soluble in water but has a lower critical solution temperature (LCST) around 31-33-degrees-C. The water filtration rate of the polyIPAAm grafted membrane varied more than 10-fold between temperatures above and below the LCST, reflecting the drastic configuration change of poly-IPAAm. The temperature sensitivity was reversible and reproducible. It is likely that the grafted chains acted as a sensor of temperature and as a valve to regulate filtration characteristics. The temperature region where the filtration rate sharply changed could be shifted to higher or lower temperature by copolymerizing IPAAm with a hydrophilic monomer, such as acrylamide, or a hydrophobic monomer, such as n-butyl methacrylate, respectively. All of the temperature-sensitive membranes remained constant in size and could respond quickly to temperature changes.