Humidity sensitive properties of copolymer of quaternary ammonium salt with polyether-salt complex

Quaternized and salt-doped copolymer of 2-(dimethylamino) ethyl methacrylate (DMAEMA) with poly(ethylene glycol) methyl ether methacrylate (PEGMEMA) was used to prepare resistive thin film humidity sensors. Their humidity sensitive properties have been characterized. The effects of the proportion of the comonomer and the amount of doped salt on the humidity sensitive properties of quaternized and salt-doped copolymer have been investigated. The humidity sensitive mechanisms of two different monomer structural units in the copolymer were discussed. The sensors based on the copolymers with different proportions of the comonomers exhibit a variety of conductivity and sensitivity for different humidities. Especially, the sensors exhibit high conductivity even at very low humidity. It is proposed that the good humidity sensitive properties are related to the introduction of salt-doped PEGMEMA in the copolymer. Copyright (C) 2009 John Wiley & Sons, Ltd.