Characterization of polymers for a capacitive-type humidity sensor based on water sorption behavior

The water sorption behavior of polymers for a capacitive-type humidity sensor was examined using three different techniques. The sorbed water in hydrophilic polymers with a pyridine or hydroxyl group was highly bound and that in less hydrophilic polymers with a carbonyl or ether group was loosely bound to the polymer as determined from the sorption analysis. Among less hydrophilic polymers, the tendency to form the clustered sorbed water molecules was higher for PEC and EC, which have an ether oxygen as the hydrogen bonding basicity. The results of this study proved that cluster formation of sorbed water of a sensing polymer was closely related to the sensor's characteristics. The polymers with a weak hydrophilic site, which have a low hydrogen bond propensity, are suitable for the capacitive-type humidity sensor. (C) 1998 Elsevier Science S.A. All rights reserved.