Synthesis and characterization of conjugated donor-acceptor copolymers of benzodipyrrolidone and naphthodithiophene

A series of D-A copolymers with naphthodithiophene (NDT) as the electron-donor (D) and benzodipyrrolidone (BDPP) as the electron-acceptor (A), namely PBDPP-NDT, PBDPP-NDT-T10, PBDPP-NDT-T20, and PBDPP-NDT-T30, were synthesized by Stille coupling polymerization. Through incorporating different contents of additional thiophene units into main chains, the photophysical and electrochemical properties of the copolymers were finely regulated. Based on strong intraolecular charge transfer transition, the polymer films exhibited broad absorption bands in the range of 400–750 nm and the maxima absorption peaks of the four copolymer films were 584, 526, 437 and 566 nm, respectively. The four D-A polymers showed narrow band gaps and the electrochemical band gaps of the polymers were 1.34, 1.61, 1.64, and 1.34 eV, respectively. All of the copolymers had excellent thermal stability and the thermal decomposition temperature was above 380 °C.