Preparation of polyaniline and self-doped polyaniline–clay nanocomposites in supercritical CO2: Synthesis and conductivity study

Supercritical CO2 (ScCO2) was used as processing medium to prepare polyaniline (PANI) and self-doped polyaniline (SPANI)–clay nanocomposites. Interfacial copolymerization of aniline (ANI) and m-aminobenzene sulfonic acid (SAN) in the presence of Cloisite 30B nano-clay powder was performed in ScCO2/water to produce PANI and SPANI–clay nanocomposites. Different ratio of aniline to SAN was used and the temperature profile during copolymerization was measured to monitor the copolymerization process. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) analysis, Fourier transform infrared spectroscopy (FTIR) and UV–vis spectroscopy were used to characterize the morphology and the structure of the resultant nanocomposites. SEM and TEM results reveal that nano-clays are fully dispersed in the ScCO2 synthesized nanocomposites, while in the atmospheric synthesize ones the nano-clays have tightly bonded agglomerated and are still stack to each others. FTIR and UV–vis results revealed that the products are in high conductive emeraldine salt state. The influences of clay loading on the conductivity of resulting nanocomposites were studied. It was found that the conductivity of nanocomposites is slightly lower than pristine polymers and decreases by nano-clay loading. Conductivity of compressed pellets of pristine PANI and SPANI were measured during the storage for different periods of times to evaluate aging properties. It was found that resulted SPANI has stable conductivity compare to the PANI nanocomposite.