Silica / polyaniline composite nanoparticle produced in an inverse microemulsion solution for the electrochromic applications

Abstract

Composite nanoparticles of silica/polyaniline were synthesized and tested as an electrochromic material. For the optical application of the particles, the size was designed to be less than 100 nm in diameter, and for the size control of the particles a microemulsion synthesis method was employed. The microemulsion solution was composed of cyclohexane, 1-hexanol, Triton X-100 and aqueous phase. A stable microemulsion composition was selected as 65.4 wt% cyclohexane, 30.4 wt% surfactant and 4.2 wt% aqueous phase, where the surfactant means a mixture of 1-hexanol and Triton X-100. Hexanol-to-Triton X-100 mixing ratio in weight was chosen as 2. It was demonstrated that silica particles could be obtained from the microemulsion solution when TEOS was added to cyclohexane and an acidic catalyst was added to aqueous phase. The preparation of the composite nanoparticles of silica/polyaniline was also performed from the microemulsion solution. Monomer aniline and a polymerization agent were added to the aqueous phase. Microstructure analysis such as TEM and BET surface area measurement showed that polyaniline is incorporated in the pores of silica structure. It was proven that the composite structure enhances the chemical stability of the material, such as resistivity to the dissolution by formic acid, while the pure polyaniline showed complete dissolution. An electrochromic property enhancement was also demonstrated for a film made of the nanoparticles. The electrochromic properties of the electrochromic films deposited on the FTO-coated glass were compared with films prepared by the deposition of pure polyaniline by a chemical polymerization. The composite films showed increased electrochemical durability.