Modulation of the Hydrophilicity on Asymmetric Side Chains of Isoindigo-Based Polymers for Improving Carrier Mobility–Stretchability Properties

Abstract

To realize high-performance and intrinsically stretchable materials for field-effect transistor (FET) devices, a plethora of approaches about structure design have been explored. Herein, we report a new approach to control the carrier mobility–stretchability properties of the polymers by tuning the hydrophilicity and asymmetric side-chain combination. A series of isoindigo–bithiophene (II2T)-based semiconducting polymers with three kinds of side chains including carbosilane side chain, semifluorinated side chain, and oligoether side chain were synthesized for investigating the structure–mobility and structure–stretchability relationships. The experimental results showed that the molecular stacking pattern and orientation of the derived polymers could be controlled by altering the hydrophilicity and asymmetric side-chain combination. The side chains of carbosilane and oligoether and a semifluorinated side chain could provide an order edge-on stacking, conformability and backbone aggregation, and an irregular solid-state aggregation, respectively. Among them, P(Si–O) with oligoether and a carbosilane side chain exhibited an enhanced μₕ of 0.56 cm² V–¹ s–¹, edge-on stacking, and aggregation behavior owing to the favorable intermolecular interaction between the oligoether side chain and the asymmetric side chain to mitigate the steric hindrance. Also, P(Si–O) possessed a remarkable stretchability of (92%,⊥, 82%,∥) orthogonal μₕ retention under 100% strain and almost unchanged μₕ was observed after 1000 stretching–releasing cycles at 60% strain. The experimental results suggested that the combination and hydrophilicity of side chain played a pivotal role in developing semiconducting polymers with a high performance and an intrinsic stretchability.