Grafting of poly(3-hexylthiophene) brushes on oxides using click chemistry

Abstract

Poly(3-hexylthiophene) (P3HT) brushes on silicon dioxide (SiO2) were prepared using a click reaction between ethynyl-terminated P3HT and an azide self-assembled monolayer (SAM). Regioregular ethynyl-terminated P3HT with molecular weight of 5900 g mol−1 and polydispersity of 1.2 was synthesized by catalyst-transfer polycondensation using Grignard metathesis mediated by a nickel-based catalyst. The azide SAM was prepared from bifunctional molecules containing azide and siloxane as click reaction precursor and surface linker, respectively. The P3HT brushes were characterized by atomic force microscopy, ellipsometry, X-ray photoelectron spectroscopy, infrared reflection absorption spectroscopy, and UV-visible spectroscopy. The grafting of P3HT brushes was studied as a function of click reaction time and the growth of the brushes is governed by a diffusion-controlled process. P3HT brushes were prepared on pre-fabricated field-effect transistor structures in order to probe the electrical properties of the brushes. The versatile synthetic methodology developed in this work can be generalized to prepare a wide variety of semiconducting conjugated polymer brushes on oxide surfaces relevant to organic electronic devices.