Enhancing the Stretchability of Polymer Semiconductors by Incorporating Di-2-thienylsulfide as the p-π Conjugation Unit into the Backbones.

Incorporating flexible conjugation breakers into conjugated polymers to develop intrinsically stretchable polymer semiconductors has garnered much attention. However, it still remains challenging to improve mechanical stretchability without compromising the charge transport property of polymer semiconductors. Herein, we report an approach to enhance the mechanical stretchability of the polymer semiconductor while largely maintaining its semiconducting performance by incorporating di-2-thienylsulfide as the p-π conjugation units into the backbone of poly-(3,6-di-(thiophen-2-yl)-diketopyrrolo-[3,4-c]-pyrrole-1,4-dione-alt-thieno-[3,2-b]-thiophen) (PDPP-TT). Compared to the parent polymer PDPP-TT, the incorporation of the p-π conjugation units induces the twisting of the backbone and weakens the interchain packing order, resulting in higher crack onset strain and better mechanical durability. The polymer semiconductor in which the molar ratio of the repeat unit with di-2-thienylsulfides is 10% exhibits a crack onset strain greater than 100% and can retain its initial charge mobility after 1000 stretching-releasing cycles under 50% strain. Our studies show that incorporation of p-π conjugation units such as di-2-thienylsulfide into backbones of polymer semiconductors provides a feasible approach to balance the stretchability and charge mobility, thus making it a promising way for future development of stretchable polymer semiconductors.