Simultaneous Enhancement of Stretchability, Strength, and Mobility in Ultrahigh-Molecular-Weight Poly(indacenodithiophene-<i>co</i>-benzothiadiazole)

Abstract

To simultaneously obtain outstanding stretchability, strength, and charge mobility of conjugated polymers (CPs) has remained a challenge for the field of stretchable electronics to date. Herein, we propose a strategy of increasing the molecular weight of a near-amorphous CP poly(indacenodithiophene-co-benzothiadiazole) (IDT-BT) to an ultrahigh level to overcome the trade-off. Detailed molecular weight-dependent study confirms that increasing the molecular weight can simultaneously enhance the mechanical and charge transport properties of IDT-BT, owing to the higher extent of chain entanglement and a larger range of charge transport along the backbone. Ultrahigh-molecular-weight (1049.6 kg mol–1, weight average) IDT-BT exhibited the highest mobility of 2.63 cm2 V–1 s–1, modulus of 1126.7 MPa, elastic recovery >80%, crack onset strain >100%, fracture strain ≥20%, and a crack-free morphology after 100 cycles of strain. To the best of our knowledge, the ultrahigh-Mw IDT-BT outperforms previously reported stretchable CPs by exhibiting enhanced elasticity, strength, and charge mobility at the same time.