Microcomposites of zirconium phosphonates with a conducting polymer, polyaniline: Preparation, spectroscopic study and humidity sensing

The microcomposites of a conducting polymer, polyaniline, with four layered zirconium phosphonates, viz. 4-sulfophenylphosphonate, 2-sulfoethylphosphonate, 4-carboxyphenylphosphonate, carboxymethylphosphonate, were prepared and characterized by wide-angle X-ray diffraction and FTIR and Raman spectroscopies. Aniline hydrochloride was proved to intercalate the hosts containing sulfonic group. The intercalation was not observed with the carboxyl-containing phosphonates. Two methods of aniline oxidation, using peroxydisulfate anion, cerium(IV) or iron(III) cations as aniline oxidants, were tested. FTIR and Raman spectra suggest that the intercalated aniline does not polymerize. Polyaniline grows on phosphonates during surface polymerization rather than to be generated as a free polymer in the bulk of reaction mixture. Conductivity varied from 10(-9)S cm(-1) to 10(-3)S cm(-1) depending on the way of preparation and the type of the phosphonate filler. The conductivity response to the ambient humidity strongly depends on the filler and suggests the possibility to apply these materials in humidity sensors.