Strategic design and synthesis of π-conjugated polymers suitable as intrinsically stretchable semiconducting materials

Main-chain engineering and side-chain engineering approaches used to design and synthesize semiconducting polymers with intrinsic ductility and/or stretchability are introduced in this review, and recent progress in this area is discussed. Main-chain engineering includes (a) conjugation-break spacer (CBS), (b) ternary copolymer, and (c) block copolymer approaches, and side-chain engineering includes (d) Y-shaped side chain, (e) graft copolymer, and (f) cross-linking approaches. A summary of the results obtained by approaches (a)–(f) demonstrates that approaches (a) and (d) tend to provide high charge mobilities (>1 cm2V−1s−1) even at 100% tensile strain. On the other hand, the mechanical properties of films prepared by these methods remain poor, with a high elastic modulus in the range of >0.1 GPa, which causes poor film ductility and stretchability. In contrast, ductile and/or elastic semiconducting materials with extremely low elastic moduli of <0.01 GPa are obtained by approaches (c) and (f), which are used to prepare thermoplastic and cross-linked elastomeric materials, respectively. For semiconducting polymers to be promising candidates in applications such as wearable electronics, electronic skins, and bioelectronics, the trade-off relationship between the electronic and mechanical performance of semiconducting polymers must be prevented by further developing and combining versatile and efficient approaches. Strategic design and synthesis of semiconducting polymers with intrinsic ductility and/or stretchability are introduced in this review. The best polymer films show high charge mobilities over 1 cm2V−1s−1 even at 100% tensile strain. On the other hand, their mechanical properties remain inadequate, with high elastic moduli over 0.1 GPa. For semiconducting polymers to be promising candidates in applications such as wearable electronics, electronic skins, and bioelectronics, the trade-off relationship between their electronic and mechanical performance must be prevented by further developing and combining versatile and efficient approaches.