Azopolymer triggered electrophoretic deposition of MnO2-carbon nanotube composites and polypyrrole coated carbon nanotubes for supercapacitors

Abstract

Poly[1-[4-(3-carboxy-4-hydroxyphenylazo)benzenesulfonamido]-1,2-ethanediyl, sodium salt] (PAZO) exhibits a number of unique physical properties, which are important for diverse applications of this functional polymer in photonics, optoelectronics, memory devices and sensors. A conceptually new strategy has been utilized for the fabrication of thin films of PAZO using electrophoretic deposition (EPD). The deposition kinetics and mechanism have been investigated and the advantages of EPD have been discussed. Our new findings in the surface and interface chemistry allowed for the development of surface modification methods, which were utilized for the electrosteric dispersion and EPD of MnO₂ nanofibers, multiwalled carbon nanotubes (MWCNT), polypyrrole (PPy) nanoparticles and PPy coated MWCNT. New method has been developed for the fabrication of PPy coated MWCNT, using bromothymol blue sodium salt as a dopant for PPy and dispersant for MWCNT. The aromatic PAZO monomers, containing chelating salicylate ligands provided multiple adsorption sites for PAZO adsorption on different materials and allowed for their efficient electrosteric dispersion. Another major finding was the possibility of efficient deposition of composites, using PAZO as a co-dispersant for MnO₂ nanofibers and MWCNT. The MnO₂ nanofibers, MWCNT, PPy nanoparticles, PPy coated MWCNT and composites, deposited by EPD, were used for energy storage in electrodes of electrochemical supercapacitors. Testing results showed beneficial effect of PAZO for the dispersion and EPD of advanced supercapacitor materials. The results of this investigation paved the way for EPD of other composites utilizing properties of different functional materials and unique physical properties of PAZO.