Humidity sensitive properties of copolymers containing phosphonium salts

(Vinylbenzyl)triphenylphosphonium chloride (VTPC) was prepared for a humidi ty-sensitive polyelectrolyte. The humidity-sensitive membranes were compose d of cross-linked copolymers with different contents of VTPC, n-butyl acryl ate (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 t he copolymers were measured, the impedance was decreased with an increase i n the content of VTPC. The impedance ranged from 10(7) Ohm to 10(3) Ohm bet ween 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 r esponse time were also measured. The humidity-sensitive characteristics of the cross-linked copolymer of VTPC, n-BA and DAEMA changed little even afte r soaking in water for 120 min. (C) 1999 Elsevier Science S.A. All rights r eserved.