Thermosensitive membranes with high mechanical strength were prepared by heterogeneous graft copolymerization of N-isopropylacrylamide (NIPAAm) onto cellophane in a nitric acid solution using cerium ammonium nitrate as an initiator, and the permeation behavior of solutes such as Lithium chloride and poly( ethylene glycol) s (PEGs) through the membranes at various temperatures was investigated. The degree of graft copolymerization of NIPAAm on cellophane depended on temperature, time, initiator concentration, and so on. The copolymer membranes having a high content of the NIPAAm moiety could be obtained at 25 degrees C for 24 h. The permeation of Li+ through the membranes was affected by temperature, i.e., the permeation rate of Li+ increased with increasing temperature up to 32 degrees C and then decreased rapidly above 35 degrees C. The permeation rate of Li+ through the copolymer membranes at 40 degrees C decreased considerably, but that at 20 degrees C decreased slightly with an increasing amount of the NIPAAm moiety in the membranes. The permeation rate of PEGs with a molecular weight more than 1000 through the cellophane-g-NIPPAm copolymer membranes was considerably suppressed and only the permeation rate of PEG300 increased with increasing temperature up to 35 degrees C and then decreased at 40 degrees C.