Synthesis, characterization, and properties of regioregular conjugated polymers containing quaterthiophene and an acceptor repeating units

Novel donor-acceptor type polymers consisting of alternating quaterthiophene and an electron withdrawing moiety, pyrazinyl or pyridinyl, have been prepared using Stille coupling approach with moderate yields. The polymers were highly soluble in common organic solvents such as tetrahydrofuran and chloroform. The structure and optical properties of the polymers were characterized by NMR, UV-vis and fluorescence spectroscopy, and cyclic voltammetry, respectively. The polymer having pyrazine unit exhibited a red-shift in both absorption and emission in comparison with those analogs containing pyridine because of strong electron withdrawing character of the pyrazinyl group. The polymer containing pyrazinyl as acceptor units also depicted decrease in its optical and electrochemical bandgap relative to those polymers containing 2,5- or 2,6-pyridine moieties. The electrochemical behavior showed facile n-doping and p-doping properties of those polymers consisting of alternating quaterthiophene and the acceptor moiety.