Unidirectional Macroscopic Alignment of Chlorobenzo[c]-[1,2,5]thiadiazole-Based Semiconducting Copolymers with Controlled Regiochemistry

Solution-processable donor–acceptor-type conjugated copolymers are considered one of the most promising alternatives to inorganic semiconductors. The introduction of strong electron-withdrawing groups in the acceptor units of the copolymers has been shown to favor fast charge transport; however, the correlation among the halogen-substituted molecular structure, solid-state packing, and charge transport properties is unclear. In this study, new chlorine-atom-substituted donor–acceptor copolymers comprising chlorobenzo[c]-[1,2,5]thiadiazole and 4,4-dihexadecyl-4H-cyclopenta[1,2-b:5,4-b′]dithiophene are synthesized and their physicochemical properties are compared with those of their unsubstituted or nitrogen-incorporated backbone analogs. In addition, the regioregularity of the synthesized copolymers is controlled to investigate the effects of regiochemistry on the polymer backbone alignment using the nanogroove method. The results demonstrate that different degrees of regioregularity in the main chains induce a substantially dissimilar effect of the nanogroove and capillary force on the orientation of the polymer backbone, long-range crystalline order, and charge transport properties of the conjugated polymers.