Elucidating the Role of Chain Stiffness in Conformational Behaviors of Conjugated Polymers in Dilute Solution via Coarse-Grained Modeling

LJ Wang and L Xu and L Chen and Z Wu and ZF Li and WJ Xia, JOURNAL OF POLYMER SCIENCE, 63, 4176-4188 (2025).

DOI: 10.1002/pol.20250525

Conjugated polymers (CPs) are characteristically distinguished by their rigid pi-conjugated backbone and flexible side chains, which play a crucial role in determining their conformational behavior in solution-a key factor influencing their performance in organic optoelectronic devices. Using coarse-grained molecular dynamics (CGMD) simulations, here, we systematically explore chain conformational behaviors of CPs in dilute solutions by elucidating the role of the backbone bending stiffness. By comparing flexible, semi-flexible, and rigid chain backbones, our results show that the effect of chain stiffness becomes more pronounced in good solvents at lower temperatures as compared to poor solvents at relatively higher temperatures. Investigating temperature effects reveals that backbone stiffness barely influences the theta-point parameter of solvent quality, indicating consistent equilibrium between attractive and repulsive forces despite varying rigidity values. Among the various molecular and processing parameters analyzed, the solvent quality parameter stands as the most significant one, driving CPs toward extended shapes in good solvents vs. causing compact collapse in poor solvents. Furthermore, our scaling analysis determines the mass scaling exponent as a reliable structural indicator across diverse CP chain stiffnesses and topologies, offering a dimensionless metric that connects simulation results with experimental measurements. These findings contribute to a deeper understanding of polymer solution behavior and offer valuable design principles for optimizing CP-based materials for their functional applications.

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