Synthetic Tailoring of Solid-State Order in Diketopyrrolopyrrole-Based Copolymers via Intramolecular Noncovalent Interactions

Abstract

Understanding the microstructures of semiconducting polymers is critical for improving the charge transport properties of polymer field-effect transistors (PFETs). A series of diketopyrrolopyrrole-based copolymers designed by implementing the concept of intramolecular noncovalent conformational locks through the functionalization of polymer backbones with fluorine atoms or methoxy groups were synthesized and compared with their unfunctionalized analogue. In contrast to the bimodal texture of the unfunctionalized polymer, the thin films of the polymer with fluorine atoms exhibit predominantly edge-on texture with much improved crystalline ordering. The thin films of the polymer modified with methoxy groups have a principally face-on texture. These dramatic differences in thin-film texture can be correlated with the polymers’ solubilities. Furthermore, the improved crystalline ordering of these semiconductor polymers enables the fabrication of high-performance PFETs: the hole mobility of the methoxy-modified polymer is reduced by half with respect to that of the unmodified polymer, whereas the hole mobility values of the fluorine-modified polymer are up to ∼6 times higher, approximately 1.32 cm 2 V –1 s –1, and exhibit pronounced thermal stability. These results provide new guidelines for the molecular design of semiconducting polymers with noncovalent conformational locks.