Polyaniline-zirconium phosphonate composites: Thermal stability and spectroscopic study

Microcomposites of zirconium 4-sulfophenylphosphonate and polyaniline (PANI) and zirconium 4-carboxyphenylphosphonate and PANI were prepared and their thermal decomposition in air and in nitrogen was studied by thermogravimetry. The products of the decomposition of the parent zirconium phosphonates as well as the composites formed with PANI were characterized by energy-dispersive X-ray analysis, elemental analysis, powder X-ray diffraction, IR spectroscopy, and Raman spectroscopy. Heating of the parent hosts and the composites in air to 850 degrees C leads to their total or almost total conversion to amorphous zirconium diphosphate. In nitrogen, on the other hand, a significant amount of carbon is retained after heating of both the hosts and the composites to 850 degrees C. The Raman spectra reveal that PANI, which is present as a thin film on the host particles in the starting composites, is converted to a carbon-like material when it is heated in a nitrogen atmosphere. The originally crystalline phosphonates become amorphous after being heated in nitrogen, which means that the heating leads to the destruction of the layered structure of these compounds. IR spectra indicate that the phosphonate particles either in the parent host or in the nanocomposites heated in nitrogen are protected against condensation to zirconium diphosphate.