Humidity sensing with weak acid-doped polyaniline and its composites

In this paper, we report the behaviour of humidity sensors with polyaniline-based conducting polymers doped with different weak acidic dopants. Changes in surface resistivity of films were monitored as a function of relative humidity. The acidic dopants used were camphosulphonic acid (CSA), diphenyl phosphate (DPPH), and maleic acid (Mac) blends of these were formed with styrene-butyl acrylate copolymer for improving the mechanical stability. The sensitivity of responding the level of relative humidity was compared for three composites wherein, although low sensitivity the Mac-doped films were found to be repeatable and more stable compared to the others. Films prepared out of styrene-butyl acrylate copolymer with different concentrations of PANI-Mac were used for sensing humidity ranging between 20 and 95% relative humidity. The films exhibited almost linear behaviour within a chosen range of humidity. (C) 2003 Elsevier B.V. All rights reserved.