Temperature-switchable vapor sensor materials based on N-isopropylacrylamide and calcium chloride

A novel temperature-switchable vapor sensor was prepared by radiation-induc ed polymerization of N-isopropylacrylamide (NIPAAm) in an alcohol solution of calcium chloride (CaCl2). The conductivity of the sensor material largel y increased in water and ethanol vapors, but decreased against acetone, tet rahydrofuran, and chloroform vapors. The data showed a high level of reprod ucibility. In addition, the conductivity increased with the rise of tempera ture in ethanol vapor, showing a slight hysteresis, while against water vap or it exhibited a tendency to decrease with temperature accompanied by a la rge hysteresis. On the other hand, a densimeter to determine the water conc entration in acetone solution was designed based on the opposite response o f polyelectrolyte to two vapors, acetone and water, resulting in a linear r esponsiveness at low water concentration. (C) 2001 Elsevier Science Ltd. Al l rights reserved.