Control of ionic transport vector using a temperature-responsive ionic gel membranes

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Temperature-responsive charged membranes were prepared by casting DMSO solution of graft copolymer of N-isopropylacrylamide and poly (vinyl alcohol)(PVA), polyanion and PVA.The membrane obtained was crosslinked in an aqueous solution of 0.025wt% glutaraldehyde and 0.1 N HCl at 5O℃ for 5 min. We measured the membrane potential in a dialysis system consisting of the membrane and KCl solutions to obtain the charge density at the temperatures : 10℃ and 50℃. The charge density increases and decreases reversibly between the two values : 0.07 mol dm^<-3> and 0.28 mol dm^<-3> within 10 min in response to stepwise changes in the temperature.In the dialysis system of the membrane and mixed KCl-CaCl_2 solutions, the concentration of Ca^<2+> ion at the low-concentration chambers increases and decreases reversibly with time in response to the stepwise changes in the temperature. This means that Ca^<2+> ions diffuse from the high-concentration chambers to the low concentration chambers at 10℃, and are transported against their concentration gradient at 50℃.In conclusion, the concentration of the bivalent ions in the low-concentration chambers in the system decreases at a temperature above the LCST and increases below the LCST.This means that the system has a negative feedback mechanism with regard to the concentration of multi-valent ions. Therefore, the temperature-responsive charged membrane will be applied for self-regulating systems which can adjust the concentration of specific solutes in the systems in response to temperature, for examples, 'intelligent' drug delivery and hemodialysis systems which have a homeostasis mechanism.