Synthesis and characterization of a main-chain donor-acceptor type low-bandgap polymer by post-functionalization of a poly(arylene ethynylene)

I report a facile synthetic route for synthesizing a main-chain donor-acceptor type polymer containing strong electron donating dialkylamino groups and strong electron accepting 1,1,4,4-tetracyanobuta-1,3-diene (TCBD) units. To accomplish this, an electron donating monomer 4,6-diethynyl-N,N,N,N-tetrahexylbenzene-1,3-diamine was successfully synthesized by converting two carbaldehyde groups in the corresponding monomer into acetylene groups using lithium trimethylsilyldiazomethane via Colvin rearrangement. This electron donating monomer was then polymerized with a carbonyl-activated diiodide monomer to afford an electron-donating π-conjugated precursor polymer with a reasonably high molecular weight, which was further reacted with TCNE via cycloaddition/retroelectrocyclization reaction under mild conditions to afford the target polymer with a low bandgap energy (Egopt=1.40eV and EgCV=1.10eV) arising from strong intramolecular charge-transfer interactions between electron donors and acceptors in the polymer.