Electroactive conjugated polymer brushes of poly(thiophene) and poly(phenylene) have been prepared via a surface-initiated Kumada-type polycondensation reaction, yielding films with a thickness up to 42 nm.

Kumada catalyst-transfer polycondensation (KCTP) has proven to be an excellent strategy toward the synthesis of well-defined conjugated polymers. In this report, Ni(0) species are reacted with surface-bound aryl bromides to yield KCTP initiators of structure (aryl)Ni(II)-Br. Surface-confined Kumada reactions are carried out with a ferrocene functionalized Grignard reagent to quantify initiator coverage, ligand exchange, and Kumada reaction kinetics. In addition, surface-initiated Kumada catalyst-transfer polycondensation (SI-KCTP) is carried out from the fabricated initiators to modify SiO(2) and ITO surfaces. Uniform poly(3-methylthiophene) films with thicknesses between 40 and 65 nm were characterized using a variety of spectroscopic and electrochemical techniques.

In this feature article, we highlight the recent developments in the chain growth polymerization mechanism of conjugated polymers. With a particular emphasis on Kumada catalyst-transfer polycondensation, this article focuses on the surface-initiated polymerization of conjugated polymers, along with the opportunities and challenges associated with this technique.

Palladium-mediated surface-initiated Kumada catalyst transfer polycondensation is used to generate poly(3-methyl thiophene) films with controlled thickness up to 100 nm. The palladium initiator density is measured using cyclic voltammetry and a ferrocene-capping agent, where the surface density is found to be 55% (1.1 × 10(14) molecules per cm(2)). UV-Vis spectroscopy and AFM show increased aggregation in palladium-initiated films due to the higher grafting density of palladium initiators on the surface. The anisotropy of the P3MT films is determined using polarized UV-Vis spectroscopy, which indicates a degree of orientation perpendicular to the substrate. Evidence that palladium can maintain π-complexation even at elevated temperatures, is also shown through the exclusive intramolecular coupling of both a phenyl and thiophene-based magnesium bromide with different dihaloarenes.

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