Structures and properties of the water-soluble self-acid-doped conducting polymer blends: Sulfonic acid ring-substituted polyaniline/poly(vinyl alcohol) and poly(aniline-co-N-propanesulfonic acid aniline)/poly(vinyl alcohol)

Blends of the water-soluble self-acid-doped conducting polyanilines, sulfonic acid ring-substituted polyaniline (SPAN) and poly(aniline-co-N-propanesulfonic acid aniline) (PAPSAH), each with poly(vinyl alcohol) (PVA) were prepared and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, electronic spectroscopy, infra-red spectroscopy, thermogravimetric analysis, conductivity measurements, atomic force microscopy, and scanning tunnelling microscopy. It was found that the incorporation of PVA has no effect on the doping levels of SPAN and PAPSAH in the blends. This is due to the higher basicity of the -N= than -OH, causing a more favourable interaction of the -SO3H group with -N=. The strong interaction of these polyanilines with PVA through hydrogen bonding between hydroxyl groups (of PVA) and amine and positively charged amine and imine sites (of SPAN and PAPSAH) leads to a decrease in hydrogen bonding among PVA subchains and to a partial miscibility. As the PVA content is higher than 70%, interconnected regions of PVA-rich phase and of SPAN-rich phase are formed such that the dilution effect of PVA on the conductivity is not large. Although SPAN has a much higher thermal undoping temperature (190 degrees C) than PAPSAH (110 degrees C), it reduces to 110 degrees C in the blends due to the occurrence of dehydration at this temperature, while for the blend of PAPSAH with PVA, its thermal undoping temperature remains unchanged. (C) 1997 Elsevier Science Ltd.