Synthesis of poly(m-phenylene) and poly(m-phenylene)-block- poly(3-hexylthiophene) with low polydispersities

Well-defined poly(m-phenylene) (PMP), which is poly(1,3-dibutoxy-m-phenylene), was successfully synthesized via Grignard metathesis polymerization. PMP with a reasonably high number-average molecular weight (Mn) of 25,900 and a very low polydispersity index of 1.07 was obtained. The polymerization of a Grignard reagent monomer, 1-bromo-2,4-dibutoxy-5-chloromagnesiobenzene, proceeded in a chain-growth manner, probably due to the meta-substituted design producing a short distance between the MgCl and Br groups and thereby making a smooth nickel species (CNiC) transfer to the intramolecular chain end (CNiBr) over a benzene ring. PMP showed a good solubility in the common organic solvents, such as tetrahydrofuran, CH₂Cl₂, and CHCl₃. Furthermore, a new block copolymer comprised of PMP and poly(3-hexylthiophene) was also prepared. The tapping mode atomic force microscopy image of the surface of the block copolymer thin film on a mica substrate showed a nanofibril morphology with a clear contrast.