Patterned Conductive Polyaniline on Si(100) Surface via Self-Assembly and Graft Polymerization

A combination of surface graft polymerization of aniline and photopatterned self-assembly monolayer (SAM) was used to generate a well-defined pattern of conductive polyaniline on a Si(100) surface. A self-assembly of phenylsilane monolayer was first generated by reacting a hydroxylated silicon surface with phenyltrichlorosilane under a dry inert (N 2 ) atmosphere. The formed SAM layer has been photopatterned under an UV laser at 263 nm through a lithographic mask. The patterned SAM was reacted with triflic acid (HOTf) under a dry inert atmosphere to remove the benzene rings from the SAM layer. The OTf groups of the triflated SAM have been substituted with aniline under a dry inert atmosphere to generate an aniline-primed substrate which was further used for the graft polymerization of aniline to prepare a patterned conductive polyaniline (PANI) layer. The composition, microstructure, and morphology of PANI grafted silicon surfaces were examined by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), scanning electron microscopy (SEM), four probe conductivity, and contact angle measurements. The surface conductivity of grafted PANI free of patterning was 23 S/cm and through the patterned wires was 21 S/cm (for the surface fraction grafted), which are larger than the usual value of the homopolymer PANI films (∼1 S/cm). Microscopy images revealed a compact grafted PANI and a high edge acuity of the pattern. The present method provides a new strategy for the generation of a pattern of conductive polymers via graft polymerization.