A charged dielectric particle in a viscous fluid confined by a spherical polarizable wall: Electrostatic force and the resultant dynamics

Physics of Fluids · 2026-02-01

Electrostatic force on a charged dielectric particle in a viscous fluid confined by an initially uncharged spherical polarizable wall, and particle dynamics driven by this force were studied using numerical simulations. The charged particle interacts with the wall through electrostatics and low-Reynolds-number hydrodynamics. The electrostatic force is due to the Coulombic interaction between charges on the particle and induced charges on the cavity wall. The induced charges result from the dielectric polarization phenomenon when the dielectric permittivity of the fluid (ϵf) and that of the wall (ϵw) are not equal. Spherical, prolate, and oblate particles were considered, respectively, to study the effect of particle shape on the electrostatic force and particle dynamics. The ellipsoidal particle's axis of revolution is assumed to be along the particle–cavity line of centers. We varied particle–fluid and fluid–wall permittivity ratios (ϵp/ϵf and ϵf/ϵw), and calculated electrostatic forces on the particles as a function of the radial position of the particle center. It was found that ϵf/ϵw is more important than ϵp/ϵf in determining the electrostatic force on the particle; when ϵf/ϵw<1 (ϵf/ϵw>1), the force points toward (away from) the wall. Under the same permittivity ratios, radial position, particle charge, and particle volume, the electrostatic force on the prolate particle is the largest. We further analyzed particle velocities and trajectories under different particle shapes and sizes. Results suggest that permittivity ratios, particle shape, particle size, and particle charge can affect particle dynamics in the cavity. This study provides insights into the dynamics of charged particles under total confinement, and forms the basis for applications including intracellular delivery and microfluidic encapsulation technologies.

Solid-State Side-Chain Functionalization of Conjugated Polymers for Expanded Chemical and Functional Versatility

Journal of the American Chemical Society · 2026-03-02

Conjugated polymers that integrate diverse chemical functionalities with high electronic performance are essential for advanced organic electronic, optoelectronic, and biointerfaced technologies. Achieving such multifunctionality typically requires grafting functional units onto polymer side chains. However, conventional solution-phase approaches remain constrained by solubility limitations, side-chain-induced packing disruptions, and challenges in preserving charge transport. Here, we introduce a solid-state side-chain functionalization strategy that exploits a swellable polar side-chain architecture and azide-alkyne click chemistry to enable efficient molecular diffusion and reaction throughout predeposited polymer thin films. This approach substantially broadens the chemical compatibility of graftable units and mitigates the adverse effects on the electrical property. Moreover, the method supports spatially selective functionalization within a continuous film, enabling the patterned incorporation of chemically distinct groups to produce spatially defined optical properties. This solid-state strategy thus provides a versatile platform for constructing conjugated polymers with expanded chemical versatility, preserved electronic performance, and programmable spatial functionality.

Lipid Composition Determines Hybrid Nanoparticle Selectivity: Beyond Membrane Mimicry in Cancer Targeting

Nano Letters · 2026-05-07

Lipid-functionalized hybrid nanoparticles (hNPs) are promising for selective cancer delivery, due to their tunable membrane interactions. Yet, whether mimicking target membrane composition enhances recognition, and which determinants govern selectivity remains unresolved. Using coarse-grained molecular dynamics, umbrella sampling simulations, and lipid-specific decomposition analyses on 40 membrane-hNP systems, we examine how individual lipid species govern hNP interactions with mammalian-like and tumor-like bilayers. Our results showed cholesterol acts as the dominant stabilizer, generating free-energy minima and driving remodeling in both bilayers. Conversely, zwitterionic lipids showed weakened interactions, limited insertion, suppressed exchange, and entropic penalties. Tumor-like membranes amplify cholesterol's role in mediating hNP-membrane recognition, facilitating deeper insertion and lipid reorganization. Strikingly, composition-matched hNPs did not preferentially bind their corresponding membrane, whereas cholesterol-enriched formulations displayed increased affinity and selectivity. Thus, lipid-composition mimicry fails as a design principle for selective recognition. These findings provide a mechanistic basis for rational lipid selection, emphasizing complementarity over membrane mimicry.

CRANBERRY: An RNA Dynamics Model with Sugar Puckering and Noncanonical Base Pairing

bioRxiv (Cold Spring Harbor Laboratory) · 2026-01-13 · 1 citations

We introduce a new coarse-grained model “CRANBERRY” that incorporates sugar puckering and non-canonical base pairing, two factors central to RNA structure and dynamics, yet rarely included in most coarse-grained models. Our model is parameterized through a contrastive divergence approach, combined with fine-tuning strategies to improve accuracy in generating disordered states, a feature that is critical for the accurate description of thermodynamics. This two-stage training procedure greatly enhances cooperative folding behavior. Due to these advances, the model’s predictive performance is comparable to that of all-atom force fields for native-state structural fluctuations. Furthermore, CRANBERRY exhibits better agreement with experimental data on stacking free energies and disordered structures measured by Small Angle X-ray Scattering. In addition, CRANBERRY can reversibly fold tetraloops with an RMSD min of 1.4 Å de novo , which continues to be challenging for all-atom models. It predicts melting temperatures in agreement with experimental values, and with a greater cooperativity than all-atom predictions.

Solid-StateSide-Chain Functionalization of ConjugatedPolymers for Expanded Chemical and Functional Versatility

Figshare · 2026-03-02

Conjugated polymers that integrate diverse chemical functionalities with high electronic performance are essential for advanced organic electronic, optoelectronic, and biointerfaced technologies. Achieving such multifunctionality typically requires grafting functional units onto polymer side chains. However, conventional solution-phase approaches remain constrained by solubility limitations, side-chain-induced packing disruptions, and challenges in preserving charge transport. Here, we introduce a solid-state side-chain functionalization strategy that exploits a swellable polar side-chain architecture and azide–alkyne click chemistry to enable efficient molecular diffusion and reaction throughout predeposited polymer thin films. This approach substantially broadens the chemical compatibility of graftable units and mitigates the adverse effects on the electrical property. Moreover, the method supports spatially selective functionalization within a continuous film, enabling the patterned incorporation of chemically distinct groups to produce spatially defined optical properties. This solid-state strategy thus provides a versatile platform for constructing conjugated polymers with expanded chemical versatility, preserved electronic performance, and programmable spatial functionality.

Dynamic Linker Distortion in Zr-MOF-808 Driven by Adsorbates: A Machine Learning and Enhanced Sampling Study

ChemRxiv · 2026-03-30

Metal--organic frameworks (MOFs) are often viewed as rigid structures. However, growing experimental evidence indicates that their metal–linker connections can be quite flexible, and this flexibility could play an important role in molecular separations and catalysis. In this work, we explore how this flexibility can be induced by different guest molecules using Zr–MOF-808 as a representative system, featuring Zr 6 (µ 3 -O) 4 (µ 3 -OH) 4 clusters connected by benzene-1,3,5-tricarboxylate (BTC) linkers. More specifically, we determine the free-energy changes due to guest-induced linker distortion at the nodes through enhanced-sampling simulations with a machine-learned interatomic potential (MLIP) trained on first-principles calculations. The resulting free energy surfaces show how different guests, namely methylamine, ammonia, and pyridine, influence the node–linker junctions, with the distortion mechanism and energetics depending strongly on guest size, binding strength to the Zr node, and hydrogen-bonding ability. At room temperature, methylamine binds strongly to the Zr node and induces a local distortion that is nearly reversible. The distortion is significant, involving complete cleavage of a Zr–O(BTC) bond and rotation of the BTC linker by nearly 60 ◦ , creating an additional adsorption site at the node that can be occupied by the guest molecule. For methylamine and ammonia, the hydrogen bonds of N–H ⋯ O(BTC) steer the distortion by pulling the linker away from the node. However, pyridine, which is larger and lacks such an H-bonding interaction, must overcome a high free energy barrier to distort the MOF; only at 373 K do entropic effects make the distorted state accessible. Such detailed analysis of guest adsorption in flexible frameworks at finite temperature, rather than in rigid zero-temperature models, has been made possible by the use of advanced sampling techniques together with MLIPs. To the best of our knowledge, our findings provide a first detailed, dynamic view of the molecular processes that underlie linker distortion across multiple adsorbates in a Zr MOF, and serve to provide a mechanistic basis for tuning the flexibility of the framework through the control of the steric and electronic properties of guest molecules.

Characterizing Defect Dynamics in Silicon Carbide Using Symmetry-Adapted Collective Variables and Machine Learning Interatomic Potentials

Journal of Chemical Theory and Computation · 2026-04-23

Silicon carbide (SiC) divacancies are attractive candidates for spin-defect qubits possessing long coherence times and optical addressability. The high activation barriers associated with SiC defect formation and motion pose challenges for their study by first-principles molecular dynamics. In this work, we develop and deploy machine learning interatomic potentials (MLIPs) to accelerate defect dynamics simulations while retaining ab initio accuracy. We employ an active learning strategy comprising symmetry-adapted collective variable discovery and enhanced sampling to compile configurationally diverse training data, calculation of energies and forces using density functional theory (DFT), and training of an E(3)-equivariant MLIP based on the Allegro model. The trained MLIP reproduces DFT-level accuracy in defect transition activation free energy barriers, enables the efficient and stable simulation of multidefect 216-atom supercells, and permits an analysis of the temperature dependence of defect thermodynamic stability and formation/annihilation kinetics to propose an optimal annealing temperature to maximally stabilize VV divacancies.

Controlled propagation of soliton bullets in an engineered strain field

Proceedings of the National Academy of Sciences · 2026-03-26

Predicting and controlling the propagation of nonlinear responses in materials is critical to a range of fields, from the manipulation of single electrons in quantum optics to the understanding of crack propagation and failure of quasi-brittle materials. Solitons, which are highly localized strain patterns that propagate and persist due to nonlinear feedback mechanisms, can be produced in liquid crystal (LC) films under high-frequency AC electric fields. In previous work using uniformly oriented films of LC, soliton bullets propagated in one preset direction perpendicular to the far-field orientation of the LC director. Here, we show that confinement of the LC between asymmetric surfaces and the introduction of strain can provide a versatile mechanism to modulate the propagation direction of solitons. Specifically, we find that soliton bullets propagate along two oblique axes, where the angle can be dynamically modulated with the electric field frequency. The origins of this behavior are understood through theory and simulations, where the forces driving soliton motion are analyzed. Importantly, asymmetric flexoelectric torques lead to frequency-dependent oblique trajectories in the presence of hybrid LC anchoring, with numerical simulations predicting asynchronous out-of-plane fluctuations that are verified in experiments. Overall, our results highlight the interplay between the nonlinear action of external fields and the far-field strain on soliton propagation. They also show that confinement can be used to control the direction of propagation of nonlinear signals and demonstrate how LCs can be used as model systems to test and predict the effects of nonlinear excitations in new material designs.

Impact of Small-Alkane Solvents on Polyolefin Hydrogenolysis over a Ruthenium Catalyst

Industrial & Engineering Chemistry Research · 2026-04-30

alkane products. This work highlights the complex impact of polymer-alkane mixtures on hydrogenolysis kinetics relevant to the design of commercial-scale plastic waste valorization processes.

Role of Crosslinking and Backbone Segmental Dynamics on Ion Transport in Hydrated Anion‐Conducting Polyelectrolytes

Advanced Functional Materials · 2025-08-29 · 2 citations

Abstract Understanding the structure‐property relationships governing ion transport in hydrated polyelectrolytes is crucial for the design and optimization of electrochemical devices. By combining experiments and simulation, the influence of polymer chain segmental dynamics and water concentration on ion transport in polyelectrolytes is investigated. The segmental dynamics of a series of thermally crosslinked poly(2‐vinylpyridine)‐based polyelectrolytes have been systematically modified by varying the degree of crosslinking. The experimental and simulation results indicate that segmental dynamics have a limited influence on ion transport in hydrated polyelectrolytes. Instead, ion transport is primarily dictated by the water concentration within the hydrated polyelectrolytes. Both crosslinked and non‐crosslinked polyelectrolytes exhibit similar conductivities when normalized for water concentrations. Compared to the widely used crosslinking method with alkyl‐diamine linkage, the thermal crosslinking approach employed here not only provides an ideal platform for studying structure‐transport relationships in polyelectrolytes but also offers a promising strategy to enhance their mechanical properties by preserving backbone rigidity without sacrificing ionic conductivity.