Humidity sensitive properties of a novel soluble conjugated copolymer: ethynylbenzene-co-propargyl alcohol

A novel soluble conjugated copolymer, ethynylbenzene-co-propargyl alcohol (EB-co-OHP), was homogeneously doped with different salts and investigated as a humidity sensitive material for the first time. Thin films of the doped polymer were deposited on interdigital gold electrodes to prepare sensors. The doping agents affect the sensing behavior of the sensors, and the LiCl-doped copolymer shows better response, in which great changes of about three orders of magnitude in both impedance and capacitance variation was observed when relative humidity was varied from 33 to 97% RH. Moreover, the logarithm of capacitance of the copolymer varied linearly with RH% in the tested humidity range and exhibited little hysteresis and high sensitivity. The impedance spectra of doped copolymers at different humidities were measured and compared, and their sensing mechanism was also investigated. (C) 2002 Elsevier Science B.V. All rights reserved.