Self-assembly of rod-coils consisting of tetraaniline and alkyl chains in different oxidation states

Abstract

Rod-coil oligomers consisting of tetraaniline and alkyl chains were synthesized and their self-assembly behavior was studied in their two different oxidation states, namely the leucoemeraldine base (LEB) and the emeraldine base (EB) states. In solutions of oligomers in the EB state, two positional isomers and cis/trans (E/Z) isomers were observed in ratios of 70 : 30 and 50 : 50, respectively. The rod-coils readily crystallized into bilayered smectic-like crystals, while their detailed crystalline structure and layer periodicities, as characterized by X-ray scattering analysis, varied depending on the oxidation state of the tetraaniline block. The periodicity of the smectic layer was larger in the EB form than in the corresponding LEB form for alkyl groups of the same length. This is attributed to the fact that the tilt of the alkyl chains with respect to the layer normal, which occurs because of the discrepancy of the interfacial areas per chain between the tetraaniline and alkyl block, is greater in the LEB state than in the EB state. The facile crystallization of the alkyl tetraanilines into layers made it possible to fabricate multilayered nanofilms consisting of alternating tetraaniline and alkyl layers on the solid substrates, providing a new material system potentially useful for organic electronic devices.