Two Novel Donor–Acceptor Copolymers Containing Benzothiadiazole Dicarboxylic Imide and Pyrene: Synthesis and Characterization
摘要
Two novel D-A copolymers, PPy-DTBDI and PPyT-DTBDI, have been synthesized based on an octyl-functionalized benzothiadiazole dicarboxylic imide (BDI) acceptor unit and an ethylhexyloxy-functionalized pyrene donor unit. These copolymers were engineered with different π-spacers (thiophene in PPy-DTBDI and bithiophene in PPyT-DTBDI) to investigate their structure–property relationships. The thermal, electrochemical, optical and molecular structure of PPy-DTBDI and PPyT-DTBDI were studied to evaluate their solid-state ordering and stability. Four 2-ethylhexyloxy chains were attached to the pyrene unit, while an octyl chain was attached to the BDI unit to enhance solubility. Cyclic voltammetry measurements revealed that PPyT-DTBDI exhibited shallower HOMO/LUMO energy levels (− 5.22/− 3.56 eV) compared to PPy-DTBDI (− 5.40/− 3.63 eV), with corresponding electrical bandgaps are 1.77 and 1.66 eV, respectively. UV–Vis studies demonstrated that PPyT-DTBDI displayed a redshifted absorption maximum at 614 nm and a lower optical band gap of 1.68 eV, compared to 573 nm and 1.76 eV for PPy-DTBDI. Both copolymers demonstrated decomposition temperatures in excess of 300 °C. Powder XRD analysis presented several sharp peaks between 4.50° and 25°, showing a π–π stacking distance of 3.77 Å and suggesting high crystalline arrangements in the solid-state. These findings provide insights into the role of spacer units in the optoelectronic behavior of polymers, highlighting their possible applications in organic photovoltaic and electronic devices.