Synthesis and characterization of novel conjugated polymers based on 3-cyclobutene-1,2-dione moiety

Three novel conjugated polymers bearing 3,4-bis(4-hexylthiophen-2-yl)-3-cyclobutene-1,2-dione unit in their main chain have been synthesized successfully in good yields through Suzuki or Stille coupling reaction. Their molecular structures have been confirmed by FT-IR, ¹H NMR and ¹³C NMR. All these copolymers exhibit broad and strong absorption bands in UV–vis region, and their optical band gaps are calculated to be 1.6–2.0 eV, suggesting that they have good coverage with the solar spectrum. These polymers have good thermostability and solubility in common organic solvents. Moreover, all these objective macromolecules possess high electron affinity of ∼3.8 eV determined from cyclic voltammetry measurement, implying that they are potential n-type polymeric photovoltaic materials.