Dipole-Tailored Isomeric Linker Enables Decoupling of Aggregation and Crystallinity in Conjugated Polymers for...

The microstructure of conjugated polymers critically influences their mechanical and electronic properties. Reducing crystallinity is a common approach to improve stretchability but often leads to diminished chain aggregation, which impairs charge transport. To address this trade-off, we introduce a dipole modulation strategy to decouple aggregation from crystallinity in conjugated polymers. A series of dipole-tailored isomeric linkers (DTLs), namely, 2,6-DTL, 3,5-DTL, and 2,4-DTL, are synthesized by varying the position of an alkoxy substituent on a benzene core and flanked by thiophene units, yielding linkers with increasing dipole moments. These linkers are incorporated into a diketopyrrolopyrrole (DPP)-based polymer backbone to regulate dipole moment and chain packing. The PDPP-(2,4)-DTL polymer, whose linker possesses the highest dipole moment and most asymmetric geometry, exhibits reduced long-range crystallinity and enhanced short-range aggregation. This optimized microstructure leads to a 4-fold increase in crack onset strain and a 1.5-fold enhancement in field-effect mobility compared to the reference polymer. Subsequently, PDPP-(2,4)-DTL is blended with the nonfullerene acceptor Y7 to form the bulk heterojunction layer of a stretchable organic photodiode. The resulting device exhibits higher external quantum efficiency (EQE) and detectivity (D*) relative to the control, maintains a D* above 10¹¹ Jones under 80% strain, and retains a stable photoresponse after hundreds of stretching cycles. These findings highlight dipole modulation as an effective strategy to tailor polymer microstructure and simultaneously enhance mechanical and electronic properties.