Humidity sensitive properties of crosslinked and quaternized poly(4-vinylpyridine-co-butyl methacrylate)

Crosslinked and quaternized copolymer of 4-vinylpyridine (4-VP) with butyl methacrylate (BuMA) was used to prepare resistive-type humidity sensors. The effect of copolymer composition and the quaternization reaction time on the humidity response have been investigated. The impedance of the sensor so prepared changes linearly for four orders of magnitude over the range of 33-95% RH, showing a high sensitivity and good linearity in semi-logarithmic scale (R2 = 0.9994). In addition, it exhibits the advantages of quick response, very small hysteresis (<1% RH) and resistance to humid environment and chemical vapor. It is proposed that the good humidity sensitive properties are related to the formation of the crosslinked network structure in the sensing film and the introduction of the butyl methacrylate in the polymer chain.