Intrinsically Stretchable\nBlock Copolymer Composed\nof Polyisobutene and Naphthalenediimide–Bithiophene-Based π‑Conjugated\nPolymer Segments for Field-Effect Transistors

Abstract

Intrinsically\nstretchable semiconducting polymers have been extensively\ndeveloped owing to their potential application in wearable and biomedical\nelectronics. However, most of the developments for stretchable semiconductors\nhave been primarily focused on <i>p</i>-type semiconducting\npolymers, and their <i>n</i>-type counterparts lag far behind.\nTherefore, we report the first investigation of the mobility–stretchability\nproperties of <i>n</i>-type conjugated block copolymers\n(BCPs). The BCPs were designed and synthesized with an ABA-type architecture\ncomprising polyisobutene (PIB) and poly(naphthalenediimide–bithiophene)\n(PNDI2T) with various compositions: ABA100 (0 wt % PIB), ABA85 (15\nwt % PIB), and ABA52 (48 wt % PIB). ABA52 is found to present a lower\nelastic modulus, higher crack-onset strain, and a lower crystallinity\nthan the analogues of ABA85 and ABA100 with or without a lower PIB\ncontent. At 0% strain, the ABA100, ABA85, and ABA52 polymers show\nelectron mobilities (μ_e) of 0.012, 0.043, and 0.0032\ncm² V^–1 s^–1, respectively.\nAt 100% strain, the ABA100, ABA85, and ABA52 polymers show μ_e retention rates of (30, 17), (14, 18), and (46, 57)% with\nstrains applied parallel/perpendicular to the channel direction, respectively.\nABA100 and ABA85 exhibit similar performance decay; in contrast, ABA52\npossesses a much improved μ_e retention due to a high\nPIB content. The result of this study indicates a proof-of-concept\nBCP design for improving the mobility–stretchability properties\nof <i>n</i>-type semiconductors, which warrants further\ninvestigation.