Humidity sensor using cross-linked poly(chloromethyl styrene)

A resistive-type humidity sensor was prepared using a poly(chloromethyl styrene) (PCMS) film which was simultaneously cross-linked and quaternized. The impedance dependence on humidity for samples with various reaction degrees was measured. The sorption isotherm curves of water vapor in the cross-linked films were obtained using the quartz crystal microbalance method for the various samples. It was found that the degree of hysteresis depends on the density of the quaternary ammonium group, which affects the diffusion coefficient of the water molecules in the film.