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Abstract The mechano‐electrical properties of poly(3‐hexylthiophene) thin films are investigated as a function of their tie‐chain content. Tie chains play an indispensable role in enabling strain‐induced structural alignment and charge‐transport enhancement in the strain direction. In the absence of sufficient tie chains, the external mechanical force cannot induce any significant polymer backbone alignment locally or crystallite reorientation at the mesoscale. These samples instead undergo brittle fracture on deformation, with cracks forming normal to the direction of strain; charge transport in this direction is hindered as a consequence. This mechanistic insight on strain alignment points to the promise of leveraging tie‐chain fraction as a practical tuning knob for effecting the mechano‐electrical properties in conjugated polymer systems. 

Abstract This work presents improved compatibility in an elastomer/π‐conjugated polymer blend through side chain functionalization of the electronic polymer. Poly[(3‐(6‐bromohexyl)thiophene)‐ran‐(3‐hexylthiophene)] (P3Br_xHT,x = 0%–100%) was synthesized (i) to improve miscibility with polybutadiene (PB) elastomer through altered π–π interactions and (ii) to covalently bond across phase‐segregated interfaces. Functionalization led to morphology with reduced domain sizes to improve crack onset strain from 7% to 40%. Furthermore, UV‐activated crosslinking reinforced mechanically weak interfaces and yielded at least an additional 40% increase in crack onset strain. Charge mobility in PB/P3Br_xHT organic field‐effect transistors showed minimal dependence on bromide concentration and no negative effects from crosslinking. Functionalization was an effective method to reduce brittleness in PB/P3Br_xHT blends through morphology modification and crosslinking to improve stability towards strain for potential stretchable electronic applications. © 2019 Society of Chemical Industry