Scientific Achievement
Morphology had little influence on the fraction of ions segregating to the interface and the anion mobilities were insensitive to the morphology once the dimensionality of the morphology was accounted for.
Upper image: Illustration of the generated microphase-separated morphologies, the lamella-like LA1 and LA2, the cylindrical morphology CY, and the gyroid-like GY.
Lower image: Eigenvalues of one-dimensional diffusivity as a function of fraction of anions that are located near the interface.
Significance and Impact
A versatile multiscale simulation framework involving atomistic and coarse-grained simulations has been established for studying transport phenomenon that covers different time and length scales.
Research Details
- With specifically trained coarse-grained force field, morphologies were constructed and later the atomistic details were re-introduced by reverse mapping method.
- The mobility of ions in microphase-separated morphologies can be roughly correlated to a linear superposition based on the fraction of bulk anions and the interfacial anions.
Notes
Atomistic simulation of microphase-separated morphology of polymeric materials is not easy since the temporal scale the atomistic simulation could achieve is extremely limited, in contrast, coarse-grained simulation could easily bypass the limitation of the temporal scale and the phase diagram for microphase-separated morphology is well-known. Thus, a multiscale simulation framework has been established to construct microphase-separated morphology at the atomistic scale by using the combination of atomistic and coarse-grained simulations.
Several simulation technics have been used, the iterative Boltzmann inversion method is used to optimize the coarse-grained force field, the adaptive resolution method is used to convert the coarse-grained morphology to the desired atomistic morphology.
We found that the morphology had little influence on both static and dynamic properties if the fractions of anion in the bulk and interfacial regions were similar throughout the investigated morphologies, which agreed well to he hypothesis that the mobility of ions can be roughly correlated to a linear superposition based on the fraction of interfacial anions.
Acknowledgements
The authors’ work on the topic of ion transport in polymer electrolytes has been generously supported by grants from the Robert A. Welch Foundation (Grant F1599) and the National Science Foundation (CBET-1706968 and DMR-1721512). The development of the multiscale simulation methodology was supported as part of the Center for Materials for Water and Energy Systems, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, under Award #DE-SC0019272. The authors acknowledge the Texas Advanced Computing Center (TACC) for the generous allocation of computing resources.
Related Publication
Zidan Zhang, Jakub Krajniak, and Venkat Ganesan, "A Multiscale Simulation Study of Influence of Morphology on Ion Transport in Block Copolymeric Ionic Liquids", Macromolecules, 54(11), 4997-5010, 2021 May 27, https://doi.org/10.1021/acs.macromol.1c00025.