Thermomechanically\nand Conformationally Consistent\nCoarse-Graining of Donor–Acceptor Polymers via Energy Renormalization\nApproach

Understanding the thermomechanical and conformational\nproperties\nof semiconducting donor–acceptor conjugated polymers (D-A CPs)\nat a fundamental molecular scale is essential for the design of high-performance\ndevices. However, the substantial computational demands of all-atom\n(AA) simulations and the complex heterogeneous structures of CPs pose\nsignificant challenges in thoroughly investigating the properties\nof CPs approaching the real devices scale. Herein, leveraging the\nwell-established framework of the energy renormalization (ER) approach,\nwe develop a temperature- and architecture-transferable chemistry-specific\ncoarse-grained (CG) model for poly(diketopyrrolopyrrole-co-thiophene)\n(PDPPT)-based D-A CPs with significantly improved computational efficiency.\nOur results show excellent agreement between AA and CG simulations\nin predicting key properties such as density, Debye–Waller\nfactor, and Young’s modulus across a wide range of temperature\nand chain architectures. Specifically, the ER-corrected CG model captures\ntrends in glass transition temperature (<i>T</i><sub>g</sub>) and mechanical properties, aligning closely with experimental data.\nThe CG model reveals that longer side chain lengths and less bulky\nbackbone conjugation units induce a lower <i>T</i><sub>g</sub> and Young’s modulus, with bulky backbone units exhibiting\nslower dynamics. The localization model accurately predicts relaxation\ntimes across different molecular architectures. Additionally, the\nCG model’s conformational properties align with experimental\ndata and theoretical worm-like chain models, showing that persistence\nlength increases with longer side chains, while bulky backbone moieties\ndecrease it. These findings deepen our understanding of the complex\ninteractions between flexible side chains and rigid backbones in CPs\nwith diverse architectures, offering important insights for the strategic\ndesign of CPs with tailored properties.