Thermogravimetric mass and infrared spectroscopic properties and humidity sensitivity of polyaniline derivatives polyvinyl alcohol composites

Humidity-sensitive polyaniline derivatives/polyvinyl alcohol (PVA) composites have been studied using thermogravimetric (TG)/mass (MS) and in situ Fourier transform infrared spectroscopy. The electrical conductivity of the poly(o-phenylenediamine) (PoPD)/PVA and poly(o-aminophenol) (PoAP)/PVA composites were linearly related with the atmospheric humidity, but there was no such linear relationship for the poly(m-phenylenediamine) (PmPD)/PVA and poly(o-toluidine) (PoTd)/PVA composites. The FTIR intensity at 3600 and 3200 cm(-1) for the PoPD/PVA and PoAP/PVA composites decreased with a decrease of humidity, indicating a removal of water molecules from the composite. For the PmPD and PoTd composites, however, the involvement of water molecules in the drying and wetting stages was not pronounced. The TG/MS analyses suggested that the PoPD/PVA and PoAP/PVA composites have two types of water: one is weakly bound to the composite and equilibriates with the atmospheric moisture, and the other is strongly bound to the composite at the PVA unit and stays there even in a dry state (<130 degrees C). Emphasis is laid on the role of these different types of water for the linear dependence of the conductivity on the atmospheric humidity.