Synthesis of electron deficient semiconducting polymers for intrinsically stretchable n-type semiconducting materials

In the future Internet of Everything (IoE) society, wearable intelligent electronic devices will receive much attention. Semiconducting polymer materials with good stress-releasing properties have been sought for development of novel intrinsically stretchable semiconducting materials that possess excellent mechanical properties and endurance toward applied strains. Recently, strategies for modulating π-conjugated polymers have been developed to produce intrinsically stretchable semiconducting materials possessing excellent electronic and stress-releasing properties. Indeed, intrinsically stretchable “ p -type” semiconducting polymer materials have been developed based on both main-chain engineering and side-chain engineering. However, only a few examples of intrinsically stretchable “ n -type” semiconducting polymer materials have been reported. In this focus review, our recent progress in main-chain engineering for development of intrinsically stretchable n -type semiconducting materials is described. The topics include four strategies, namely, (i) a conjugation-break spacer approach, (ii) a block copolymer approach, (iii) an all-conjugated statistical terpolymer approach, and (iv) a sequence random copolymer approach, in which specially designed stress-relaxation units or sequences are incorporated along the main chains of naphthalene-diimide-based n -type semiconducting polymers.