Temperature-sensitive switch from composite poly(N-isopropylacrylamide) sponge gels

Thermally sensitive polymers change their properties with a change in envir onmental temperature in a predictable and pronounced way. These changes can be expected in drug delivery systems, solute separation, enzyme immobiliza tion, energy-transducer processes, and photosensitive materials. We have de monstrated a thermal-sensitive switch module, which is capable of convertin g thermal into mechanical energy. We employed this module in the control of liquid transfer. The thermally sensitive switch was prepared by crosslinki ng poly(N-isopropylacrylamide) (PNIPAAm) gel inside the pores of a sponge t o generate the composite PNIPAAm/sponge gel. This gel, contained in a polyp ropylene tube, was inserted into a thermoelectric module equipped with a fi ne temperature controller. As the water flux through the composite gel chan ges from 0 to 6.6 x 10(2) L m(-2) h, with a temperature change from 23 to 4 0 degrees C, we can reversibly turn on and off the thermally sensitive swit ch. (C) 2000 John Wiley & Sons, Inc.