Intrinsically Stretchable Block Copolymer Composed of Polyisobutene and Naphthalenediimide-Bithiophene-Based π-Conjugated Polymer Segments for Field-Effect Transistors

Intrinsically stretchable semiconducting polymers have been extensively developed owing to their potential application in wearable and biomedical electronics. However, most of the developments for stretchable semiconductors have been primarily focused on p-type semiconducting polymers, and their n-type counterparts lag far behind. Therefore, we report the first investigation of the mobility-stretchability properties of n-type conjugated block copolymers (BCPs). The BCPs were designed and synthesized with an ABA-type architecture comprising polyisobutene (PIB) and poly(naphthalenediimide-bithiophene) (PNDI2T) with various compositions: ABA100 (0 wt % PIB), ABA85 (15 wt % PIB), and ABA52 (48 wt % PIB). ABA52 is found to present a lower elastic modulus, higher crack-onset strain, and a lower crystallinity than the analogues of ABA85 and ABA100 with or without a lower PIB content. At 0% strain, the ABA100, ABA85, and ABA52 polymers show electron mobilities (μe) of 0.012, 0.043, and 0.0032 cm2 V-1 s-1, respectively. At 100% strain, the ABA100, ABA85, and ABA52 polymers show μe retention rates of (30, 17), (14, 18), and (46, 57)% with strains applied parallel/perpendicular to the channel direction, respectively. ABA100 and ABA85 exhibit similar performance decay; in contrast, ABA52 possesses a much improved μe retention due to a high PIB content. The result of this study indicates a proof-of-concept BCP design for improving the mobility-stretchability properties of n-type semiconductors, which warrants further investigation.