Donor-acceptor polymers by solid state eutectic melt reaction for optoelectronic applications

We report, the synthesis of novel donor–acceptor conjugated polymers based on benzo[1,2-b:4,5-b′]dithiophene (BDT) donor and 4,7-bis(5-bromothiophen-2-yl)benzo[c] [1,2,5]thiadiazole (DTBT) acceptor by solvent-free eutectic melt polymerization reaction (EMP). The most important fact is, reaction between solid reactants actually proceeds through bulk liquid phases, due to the formation of eutectics between the reactants and product(s) and any evolution of heat. In the present study, crystalline solid with moderately high vapor pressure and low melting temperature such as naphthalene is explored for forming eutectics in melt polymerization reaction. The HOMO and LUMO energy levels of the polymer P2 synthesized by EMP were found to be −5.30 eV and −3.77 eV. Optical bandgap was determined to be 1.53 eV. The solid-state reactions are important not only due to their high efficiency and selectivity but also for their more economical and eco-friendly procedures involved in the reaction.