Investigating the effect of sidechains on self-assembly of semiconducting polymer using a multiscale modeling approach

Modern semiconducting polymers (SCP) typically contain electron donor-acceptor backbone structures, π bridges, and side chains. Owing to their unique functionalities, such as excellent power conversion efficiency, scalability, stretchability, and highly tunable structures, SCPs have been advancing a broad range of applications, comprising solar cells, organic light-emitting diodes, implantable electronics, and beyond. Although various SCPs have been proposed in recent years, a predictive framework for discovering long-lasting and robust SCPs while maintaining high charge mobility remains unclear and time-intensive, typically attributed to their complex molecular interactions between the backbone and the side chains, as well as intricate backbone-backbone interactions. In this study, we develop a multiscale modeling framework to predict BnDT-FTAZ assembly and investigate the phase behavior under various sidechain architectures. We utilize DFT to develop forcefields (FF) among homo- and heterogenous moiety pairs from the backbone and sidechains, describing the nonbonded interactions (e.g., van der Waals and Coulombic interactions). To examine the effectiveness of the new FF, we deploy the DFT-constructed forcefields and perform all-atomic molecular dynamics (AAMD) simulations to observe the ordering competition between the backbones and the sidechains at various temperatures, investigating the intramolecular conformation distribution and the intermolecular configuration distribution. We discuss further development of coarse-grained modeling for larger-scale simulations using the Flory-Huggins χ(T) parameters.