Synthesis and properties of core–shell halloysite–polyaniline nanocomposites

We consider physico-chemical specificity (open circuit potential and pH changes) of the chemical oxidative aniline polymerization in the presence of halloysite nanotubes (HNTs) and morphology, structure and properties of the new nanocomposites of HNTs with polyaniline (PANI) doped by p-toluenesulfonic acid. We find that specificity of the PANI properties in such nanocomposites appears obviously due to adsorption on the HNTs surface and specific interactions of all participants of the polymerization process. The study of the open circuit potential and pH changes in the polymerization system and properties of the synthesized HNT/PANI nanocomposites revealed the strong dependence of their morphology, molecular structure, conductivity, thermostability and sensor behavior on the contents of the doped PANI. These findings indicate existence of specific interactions between the PANI component and the HNT surface, which significantly improved properties of the PANI component in the synthesized HNT/PANI nanocomposites as compared with that of the pure PANI. The best thermostability and sensing behavior were found for the synthesized HNT/PANI nanocomposites with the lowest contents of the doped PANI. In particular, the strongest sensor responses to gaseous ammonia are observed in the case of HNT/PANI nanocomposite with lowering the doped PANI content. This work shows for the first time applicability of HNT/PANI nanocomposites for gas sensing.