Humidity sensitive properties of copolymers containing phosphonium salts

(Vinylbenzyl)triphenylphosphonium chloride (VTPC) was prepared for a humidity-sensitive polyelectrolyte. The humidity-sensitive membranes were composed of cross-linked copolymers with different contents of VTPC, n-butyl acrylate (n-BA) and 2-(N,N-dimethylaminoethyl)methacrylate (VTPC/n-BA/DMAMA = 10/35/0, 10/45/0, 10/35/4.5 and 10/35/9). When impedance characteristics of the copolymers were measured, the impedance was decreased with an increase in the content of VTPC. The impedance ranged from 10(7) Ohm to 10(3) Ohm between 50% RH and 95% RH, which was required for a humidity sensor operating at high humidity or a dew point. Temperature dependence, hysteresis and a response time were also measured. The humidity-sensitive characteristics of the cross-linked copolymer of VTPC, n-BA and DAEMA changed little even after soaking in water for 120 min. (C) 1999 Elsevier Science S.A. All rights reserved.