Multiscale Simulation for Conducting Conjugated Polymers from Solution to the Quenching State

Abstract

Innovation in modern material science exploiting conducting conjugated polymers imperatively demands fundamental knowledge of single-chain conformations from solution to the quenching state. This urgent goal, however, poses a stringent challenge to existing simulation schemes, especially when the polymer of interest possesses simultaneously a high molecular weight and anisotropic local interaction forces, such as hydrogen-bond (HB) and pi-pi interactions. Considering a standard case with polyaniline emeraldine base (PANI-EB), widely used as the conducting layer in polymer-based optoelectronic devices, this paper introduces how the current difficulty may be circumvented by using a multiscale simulation scheme that takes advantage of a systematic mapping and back-mapping between atomistic molecular dynamics (AMD), coarse-grained molecular dynamics, and coarse-grained Langevin dynamics (CGLD). Whereas a self-consistent CGLD simulation greatly facilitates reaching representative long-chain conformations in specific solvents, the back-mapped AMD simulation permits scrutiny into the effects of localized HB and pi-pi interactions on quenched chain morphologies. The basic idea behind this multiphase simulation scheme for conducting conjugated polymers has been consolidated by the central observation for PANI-EB: whereas segmental van der Waals interactions dominate fundamental single-chain properties in solution (i.e., persistence length, solvent quality, and chain diffusivity), the anisotropic HB and pi-pi interactions accordingly "trap" the quenched chain to a morphology closely mimicking that in the prior solution state-the first microscopic evidence of the so-called "memory effect." Notably, the central features disclosed for PANI-EB as well as the multiscale simulation strategy proposed for tracking single-chain conformations from solution to the quenching state are asserted to hold for typical conducting conjugated polymers that possess, ubiquitously, a semiflexible backbone and localized interaction forces.