Preparation of poly(3-hexylthiophene) conjugated polymer brush films from amine-terminated surfaces

Conjugated polymer brush (CPB) films are more robust and exhibit more vertically aligned polymer chains than their spun-cast analogs. We prepare CPB films of poly(3-hexylthiophene) (P3HT) by coupling an amine-terminated surface (ATS) formed from (3-aminopropyl)triethoxysilane (APTES) on Si/SiO₂ to 4-bromobenzoic acid using standard, inexpensive peptide coupling reagents. The resulting terminal bromobenzene is reacted with Pd(PtBu₃)₂ and immersed in the monomer solution. X-ray photoelectron spectroscopy, spectroscopic ellipsometry and static water contact angle measurements confirm the surface chemistry at each stage of P3HT CPB preparation. Atomic force microscopy(AFM) and UV–vis spectrophotometry indicate that the CPB films prepared by this method exhibit similar morphology and optical properties to those produced from other methods of poly(3-alkylthiophene) CPB film preparation. Variations of the standard approach, such as using a pre-synthesized silane counterpart or with (11-aminoundecyl)triethoxysilane, show comparable film morphologies by AFM. This method is used to produce the first CPB film of poly(3-dodecylthiophene), showing its utility for exploring CPB films of more sterically demanding polymers. Peptide coupling is used to prepare an analogous functionalized thiol for initiating P3HT CPB film growth from Au surfaces, and microcontact printing with this thiol allows preparation of the first patterned CPB film of P3HT.