Leveraging chemical crosslinking to reconcile elastic recovery rate and ductility in high-mobility stretchable conjugated polymers

Abstract

Despite recent advances in stretchable polymer semiconductors, the trade-off between charge mobility and mechanical properties remains outstanding using conventional physical or chemical strategies. Herein, we introduce transesterification crosslinking in hydroxy-modified poly(indacenodithiophene-alt-benzothiadizole)s (OH–IDTBT-5%) using a polyurethane elastomer crosslinker containing a polycaprolactone segment (PU–PCL), to simultaneously enhance the elastic recovery rate, elastic modulus (∼1.5 GPa) and hole mobility, while maintaining exceptional ductility (COS > 100%, ε_F ∼ 30%). The crosslinked network restricts plastic deformation, yielding an outstanding elastic recovery rate (>90% at 4% strain) with delayed plastic deformation onset strain (PdOS ∼ 100%). Notably, the crosslinking reaction passivated detrimental hydroxy groups and enhanced mobility to 2.13 cm² V⁻¹ s⁻¹, which remained relatively consistent even after 500 stretching cycles at 70% strain. Importantly, the crosslinking films exhibited excellent robustness against organic solvents by retaining over 90% fraction after soaking. Our strategy provides an opportunity for high-performance stretchable semiconductors, by overcoming not only the trade-off between charge transport properties and mechanical durability in general, but also the sacrifice of ductility in chemical crosslinking systems.