Computational investigation of dynamical heterogeneity in ionic liquids based on the restricted primitive model

The generalized solutions of the dimensionality reduction problem in diffusion–reaction systems have been found for the first time by rigorously decoupling probability functions. Numerically exact results are obtained by straightforwardly applying the generalized solution to three models: protein‐DNA binding model (3D‐1D reduction), surface‐mediated diffusion (3D‐2D reduction), and line‐mediated diffusion cases (2D‐1D reduction). The results are confirmed by Monte Carlo simulations.

“…Lattice‐based Monte Carlo simulations 33–36 were performed to confirm the theoretical predictions for these models. An initially implanted molecule moves via a random walk.…”

Section: Resultsmentioning

confidence: 99%

Dimensionality reduction in diffusion–reaction systems

Park,

Kim,

Kim

2023

“…The dynamic heterogeneity is observed in various types of materials including glasses, gels, polymers, and biological systems. [17][18][19][20] The dynamic heterogeneity is, therefore, considered as a critical factor to the transport properties in those complex materials. There were several experimental evidences that dynamic heterogeneity were also present in OIPCs.…”

Section: Introductionmentioning

confidence: 99%

Simulation studies on the dynamic heterogeneity of organic ionic plastic crystals

Park

Sung

2023

Organic ionic plastic crystals (OIPCs) are one of promising solid‐state electrolytes (SSEs) for all‐solid‐state batteries. OIPCs consist of organic ions that form crystalline solid phases. It is a challenging but critical task in the development of SSEs to improve the ion conductivity of lithium ions in such crystalline solid phases. We discuss our recent simulation studies on the transport mechanism of ions in OIPCs and show that the dynamic heterogeneity should be a key to the transport mechanism. We aim to show that both translational and rotational dynamic heterogeneities should play an important role in understanding the ionic conductivity in SSEs. We found from our simulations that the introduction of dopants and defects into OIPCs facilitated both the dynamic heterogeneity and the ion conductivity significantly. We also found that the polarizability of matrix organic ions could contribute to the rotational and conformational relaxations of organic ions in OIPCs.

Stretchable conducting polymer PEDOT:PSS treated with hard‐cation‐soft‐anion ionic liquid designed from molecular modeling

Lansac,

Choi,

Jang

2024

PEDOT:PSS, an ionic polymer mixture of positively‐charged poly‐3,4‐ethylenedioxythiophene (PEDOT+) and negatively‐charged poly‐styrenesulfonate (PSS−), is a water‐processable and environmentally‐benign organic semiconductor and electrochemical transistor, which plays a key role in organic (bio)electronic devices. However, pristine PEDOT:PSS films form 10‐to‐30‐nm granular domains, where conducting‐but‐hydrophobic PEDOT‐rich cores are surrounded by hydrophilic‐but‐insulating PSS‐rich shells. Such morphology makes PEDOT:PSS water‐soluble and thermally stable but very poor in conductivity. A tremendous amount of effort has been made to enhance the conductivity of PEDOT:PSS by restoring the extended conduction network of PEDOT. Recently, remarkable ~5000‐fold improvements of conductivity have been achieved by mixing PEDOT:PSS with proper ionic liquids (ILs). In a series of free energy estimations using density functional theory calculation and molecular dynamics simulation, we have demonstrated that the classic hard‐soft acid–base (or cation‐anion) principle of chemistry plays an important role in such improvements. Ion exchange between PEDOT+:PSS− and A+:X− ILs helps PEDOT+ to decouple from PSS− and to grow into large‐scale conducting domains of π‐stacked PEDOT+ decorated by IL anions X−. Thus, the most spontaneous decoupling between soft (hydrophobic) PEDOT+ and hard (hydrophilic) PSS− would be induced by strong interaction with soft anions X− and hard cations A+, respectively. Such hard‐cation‐soft‐anion principles have led us to design ILs containing extremely hydrophilic (i.e., protic) cations and hydrophobic anions. Not only they indeed improve the conductivity of PEDOT:PSS but also enhance its stretchability as well. In summary, our modeling offered molecular‐level insights on the morphological, electrical, and mechanical properties of PEDOT:PSS and a molecular‐interaction‐based enhancement strategy for intrinsically stretchable conductive polymers.