Oligoaniline-contained electroactive silsesquioxane precursor for synthesizing novel siliceous materials

As analogues of the well-known conducting polymer polyaniline, aniline oligomers have been extensively investigated because of their well-defined structure, good solubility, and electroactivity. In this study, we demonstrated for the first time the successful and high-yield synthesis of a novel electroactive organo-bridged silsesquioxane precursor, N,N'-bis(4'-(3-triethoxysilylpropyl-ureido)phenyl)-1,4-quinonenediimine (TSUPQD), which covalently incorporates the emeraldine form of amine-capped aniline trimer into silica frameworks via one-step coupling reaction with triethoxysilylpropyl isocyanate (TESPIC) under a mild condition. Subsequently, detailed characteristics of the resulting silsesquioxane compound along with morphological measurement were systematically studied by using spectroscopic methods, such as Fourier-transform infrared (FTIR) spectra, mass spectra (MS), nuclear magnetic resonance (NMR) spectroscopy, and X-ray powder diffraction (XRD). In addition, its electrochemical behavior was explored by UV-vis spectra and cyclic voltammetry showing that its intrinsic electroactivity was maintained upon protonic acid doping and presented two distinct oxidative states in reversible cyclic voltammetry, similar to that of polyaniline. Furthermore, the sol-gel reactions of TSUPQD with various amounts of tetraethyl orthosilicate (TEOS) were carried out to afford new electroactive hybrid siliceous materials whose properties were also studied.