Solvent effects on the morphology and electrical conductivity of a D‐A random copolymer with low band gap

Abstract

D-A copolymer systems have unique characteristics, such as low band gap and ambipolar nature, which are important to design electronic polymer devices. In this contribution, we synthesized and characterized a D-A random copolymer containing bis-3-hexylthiophene-benzothiadiazole as acceptor unit and 9,9-dioctylfluorene as donor unit. We show that the polymeric film morphology depends of the Hansen solubility parameters, evaporation rate, and surface tension of the solvent. Chloroform, toluene, and 1,2,4-trichlorobenzene (TCB) promote the formation of self-assembled structures due to breath-figure mechanism. In contrast, THF causes aggregation and phase separation that affect negatively the electrical conductivity of the copolymer film. Among the solvents analyzed, TCB is the one with the highest molecular interaction with the copolymer synthetized in this work.