Synthesis and Characterization of Fully Conjugated Donor–Acceptor–Donor Triblock Copolymers

Abstract

A synthetic approach is established to provide a monofunctional telechelic poly(3-octylthiophene) (P3OT) bearing a single bromine-substituted end group that is of potential use in the preparation of well-defined block copolymers. Telechelic P3OT was prepared via a chain growth process by a catalyst-transfer condensation polymerization (CTCP) of 5-bromo-4-octyl-2-thienylmagnesium iodide initiated by a phenylnickel(II) initiator. Optimization of the conditions for quenching the reaction allowed for the installation an α-bromo functionality at the terminus of the polymer. We demonstrate the utility of this well-defined monofunctional polymer, Ph–P3OT–Br, by coupling it to a poly(quinoxaline) (PQ) bearing boronate ester end groups to provided a new class of donor–acceptor–donor (D–A–D) triblock copolymers. The formation of the triblock copolymers was confirmed by gel-permeation chromatography (GPC) and 1H NMR spectroscopy. The optical properties of the polymers were investigated using UV–visible absorption and fluorescence spectroscopy. Efficient quenching of the fluorescence from the individual blocks of the triblock copolymers is consistent with the occurrence of electron transfer. AFM images illustrate a nanoscale phase separation of the electron-rich P3OT and electron-poor PQ blocks.