A resistive-type humidity sensor based on crosslinked polyelectrolyte prepared by UV irradiation

2-(Dimethylamino) ethyl methacrylate was quaternized with n-butyl bromide and then copolymerized with 1,4-divinylbenzene to obtain a resistive-type crosslinked polyelectrolyte humidity sensitive material by UV irradiation at low temperature (≤60 °C) in a short time (<1 h). The humidity sensor based on the crosslinked polyelectrolyte was aged by immersion in water for 5 min to remove water-soluble materials. The aged sensor exhibited a high sensitivity (impedance change from ∼107 to 103 Ω in the humidity range of 22–97% RH), small hysteresis (∼1% RH) and fast response (t90% ∼9 and 32 s for adsorption and desorption between 33% RH and 97% RH, respectively). In addition, it showed good durability as indicated by slight impedance change after immersion in water. The effects of molar ratio of crosslinking agent to quaternary ammonium salt, UV irradiation time and environment temperature on its humidity sensing properties were investigated.