Chang Yun Son

Solid-state polymer electrolytes and high-concentration liquid electrolytes, such as water-in-salt electrolytes and ionic liquids, are emerging materials to replace the flammable organic electrolytes widely used in industrial lithium-ion batteries. Extensive efforts have been made to understand the ion transport mechanisms and optimize the ion transport properties. This perspective reviews the current understanding of the ion transport and polymer dynamics in liquid and polymer electrolytes, com

Molecular dynamics study of ionic liquids (ILs) is a challenging task. While accurate fully polarizable atomistic models exist, they are computationally too demanding for routine use. Most nonpolarizable atomistic models predict diffusion constants that are much lower than experiment. Scaled charge atomistic models are cost-effective and give good results for single component ILs but are in qualitative error for the phase behavior of mixtures, due to inaccurate prediction of the IL cohesive ener

Electrostatic interactions near surfaces and interfaces are ubiquitous in many fields of science. Continuum electrostatics predicts that ions will be attracted to conducting electrodes but repelled by surfaces with lower dielectric constant than the solvent. However, several recent studies found that certain "chaotropic" ions have similar adsorption behavior at air/water and graphene/water interfaces. Here we systematically study the effect of polarization of the surface, the solvent, and solute

An explicit treatment of electronic polarization is critically important to accurate simulations of highly charged or interfacial systems. Compared to the iterative self-consistent field (SCF) scheme, extended Lagrangian approaches are computationally more efficient for simulations that employ a polarizable force field. However, an appropriate thermostat must be chosen to minimize heat flow and ensure an equipartition of kinetic energy among all unconstrained system degrees of freedom. Here we i

Recently, the interest in charged polymers has been rapidly growing due to their uses in energy storage and transfer devices. Yet, polymer electrolyte-based devices are not on the immediate horizon because of the low ionic conductivity. In the present study, we developed a methodology to enhance the ionic conductivity of charged block copolymers comprising ionic liquids through the electrostatic control of the interfacial layers. Unprecedented reentrant phase transitions between lamellar and A15

Cytochrome <i>c</i> oxidase (CcO) is a transmembrane protein that uses the free energy of O₂ reduction to generate the proton concentration gradient across the membrane. The regulation of competitive proton transfer pathways has been established to be essential to the vectorial transport efficiency of CcO, yet the underlying mechanism at the molecular level remains lacking. Recent studies have highlighted the potential importance of hydration-level change in an internal cavity that co

Achieving superionic conductivity from solid-state polymer electrolytes is an important task in the development of future energy storage and conversion technologies. Herein, a platform for innovative electrolyte technologies based on a bifunctional polymer, poly(3-hydroxy-4-sulfonated styrene) (PS-3H4S), is presented. By incorporating OH and SO₃ H functional groups at adjacent positions in the styrene repeating unit, "intra-monomer" hydrogen bonds are formed to effectively weaken th

The behavior of polymers in complex solvents is interesting from a fundamental perspective and of practical importance from the standpoint of polymer processing. There has been recent interest in the conformational and dynamic properties of polymer in room temperature ionic liquids, with conflicting predictions from computations using models with different resolutions and conflicting results of experiments from different groups. In this work, we develop a first-principles, nonpolarizable united

Abstract Conjugated polymer (CP)/carbon nanotube (CNT) composites have been actively used for thermoelectrics for more than a decade. Thermoelectric performance of CP/CNT composites is greatly improved compared with that of the individual components; however, the underlying origin of the performance improvement remains vague, without clear explanations at the molecular scale. Moreover, the nature of the heterogeneous system limits quantitative analysis and restricts physical understanding of the

Herein, by choosing few-nm-thin two-dimensional (2D) nanocrystals of MOF-5 containing in-planner square lattices as a modular platform, a crystal lattice-guided wet-chemical etching has been rationally accomplished. As a result, two attractive pore patterns carrying Euclidean curvatures; precisely, plus(+)-shaped and fractal-patterned pores via ⟨100⟩ and ⟨110⟩ directional etching, respectively, are regulated in contrast to habitually formed spherical-shaped random etches on MOF surface. In agree

A universal approach for enhancing water affinity in polymer photocatalysts by covalently attaching hydrophilic photocrosslinkers to polymer chains is presented. A series of bisdiazirine photocrosslinkers, each comprising bisdiazirine photophores linked by various aliphatic (CL-R) or ethylene glycol-based bridge chains (CL-TEG), is designed to prevent crosslinked polymer photocatalysts from degradation through a safe and efficient photocrosslinking reaction at a wavelength of 365 nm. When employ

Electrostatic interactions play a dominant role in charged materials systems. Understanding the complex correlation between macroscopic properties with microscopic structures is of critical importance to develop rational design strategies for advanced materials. But the complexity of this challenging task is augmented by interfaces present in the charged materials systems, such as electrode-electrolyte interfaces or biological membranes. Over the last decades, predictive molecular simulations th

Living cells efflux intracellular ions for maintaining cellular life, so intravital measurements of specific ion signals are of significant importance for studying cellular functions and pharmacokinetics. In this work, de novo synthesis of artificial K⁺ -selective membrane and its integration with polyelectrolyte hydrogel-based open-junction ionic diode (OJID) is demonstrated, achieving a real-time K⁺ -selective ion-to-ion current amplification in complex bioenvironments. B

By using the recently developed method for solving the Fredholm integral equations of the second kind, we derive a very accurate expression for the steady-state rate constant of diffusion-influenced bimolecular reactions involving long-range reactivity. We consider the general case in which the reactants interact via an arbitrary central potential and hydrodynamic interaction. The rate expression becomes exact in the two opposite limits of small and large reactivity, and also performs very well