Morphology Manipulation in Non-Halogenated Solvent Printed Stretchable Polymer Films via Sequential Optimization of Molecular Weight and Thermal Aggregation

Printing high-performance stretchable conjugated polymer film from non-halogenated solvents is critical for the scalable manufacturing of large-area wearable electronics. However, the suboptimal morphological control in these films severely limits their mechanical and electrical performance. Herein, we optimize the morphology of non-halogenated solvent-printed stretchable conjugated films based on blends of conjugated polymer poly(3-(5-(5-methylselenophen-2-yl)thiophen-2-yl)-6-(5-methylthiophen-2-yl)-2,5-bis(4-octyltetradecyl)-2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione) (P(TDPP-Se)) and the elastomer polystyrene-block-poly(ethylene-ranbutylene)-block-polystyrene (SEBS) via combined control of molecular weight and processing temperature. Selecting a P(TDPP-Se) with intermediate molecular weight ensures favorable solubility alongside robust aggregation in the non-halogenated solvent toluene. Subsequent printing at a mild temperature at 60°C enables controlled pre-aggregation in initial solution and relatively short disaggregation process. This yields an optimal balance between chain alignment and molecular ordering in solid film, producing moderately crystalline and aligned P(TDPP-Se) nanofiber networks embedded within SEBS matrix. During stretching, the cooperative deformation of P(TDPP-Se) nanofibers and SEBS domains, the recrystallization of P(TDPP-Se) chains, and nanovoid propagation collectively dissipate strain energy, thereby preserving partially interconnected charge-transport pathways. In contrast, the highly crystalline thick fibers formed at 30°C and dense, highly aligned fine fibrils produced at 90°C are both prone to fragmentation under strain. Consequently, the film processed at 60°C exhibits a high charge mobility (1.25 cm 2 V −1 s −1 ) and alleviated electrical degradation during stretching, significantly outperforming the films processed at other temperatures. This work provides a systematic morphology optimization strategy for the environmentally benign and scalable fabrication of high-performance stretchable conjugated polymer films.