Shiling Yuan

Understanding the microstructural self-assembly and mechanical response of unaged and oxygen-aged asphaltenes within oil droplets is essential for elucidating the stabilization mechanisms of weathered crude oil emulsions generated during oil-spill weathering and remediation. Herein, quantum chemical calculations and multiscale molecular dynamics simulations were employed to systematically evaluate the impact of oxidative molecular evolution on multibody aggregation and droplet surface properties. Results revealed that aging drove asphaltenes from a bulk-dispersed state to pronounced interfacial enrichment, narrowing the radial distribution width by 51% (from 43 Å to 21 Å) and enhancing local structural ordering (radial distribution functions peak) by 10-fold via face-to-face aromatic stacking. This interfacial orientation exposed edge heteroatoms, causing the droplet hydrophilic surface area to surge by 175% (from 16 to 44 nm2) at a 20 wt % mass fraction, while the single-molecule hydration energy intensified by 84% from −2.09 to −3.85 kcal/mol. Conversely, under dynamic nonequilibrium perturbations, polar functionalization compromised the skeletal compatibility with nonpolar light oil fractions, reducing the bulk framework-solvent coupling energy to 56% of the unaged asphaltene system. Consequently, the aged droplet deformation increment (63 nm2) reached 3.9 times that of the unaged counterpart (16 nm2). This study unravels a competitive mechanism between aging-induced 2D interfacial rigidity and 3D bulk cohesion degradation, providing a critical molecular framework for designing targeted demulsifiers to accelerate phase separation in weathered crude oils.

ReaxFF molecular dynamics simulations were used to examine the thermal degradation of the solid electrolyte interphase (SEI) at a graphite/electrolyte interface in lithium-ion batteries. Above 450 K, the initially stratified SEI, comprising an inorganic inner layer and an organic outer layer, progressively transforms into a disordered and porous mixed phase. Heating accelerates electrolyte decomposition, broadens the product speciation, promotes CO2 and HF evolution, and destabilizes the interface. The dominant bond-breaking sequence is C–O cleavage, followed by Li–O and P–F cleavage. These events are coupled in a degradation network rather than occurring independently. The results provide atomistic insight into thermally driven SEI failure and identify design targets for thermally robust battery interfaces.

Disruption of the stratum corneum (SC) lipid matrix compromises the skin barrier function; however, the molecular mechanisms by which exogenous lipids promote its repair remain unclear. Here, all-atom molecular dynamics (MD) simulations were employed to investigate how initially dispersed lipid molecules and preassembled nanoparticles influence the direct rearrangement behavior of exogenous lipids at a localized defect in ceramide (CER)/cholesterol (Chol)/free fatty acid (FFA) ternary lipid bilayers. The results show that barrier repair efficiency depends strongly on both delivery format and lipid species. Initially dispersed lipids, limited by inefficient random diffusion, exhibit effective local repair but constrained overall efficiency. In contrast, preassembled lipid nanoparticles follow an “adsorption-spreading-reassembly” pathway, where localized high-concentration delivery overcomes diffusional barriers and significantly enhances repair efficiency. The three lipid species exhibit different molecular repair mechanisms at the damage site, governed by their unique molecular structures: CER shows stronger enrichment, FFA displays greater diffusion and dynamic reorganization, and Chol forms a denser and more stable bilayer. This study provides a molecular-level reconstruction associated with barrier repair and offers guidance for developing more effective topical lipid repair formulations.

Small alkaloids such as nicotine and its major metabolite, cotinine, are widely present in biological and environmental systems, yet their membrane interaction mechanisms and related cytotoxic effects remain poorly quantified. Here, molecular dynamics simulations combined with umbrella sampling were used to investigate the adsorption, distribution, orientation, and transmembrane behavior of nicotine and cotinine in DPPC bilayers. Both molecules rapidly migrated from bulk water to the water–lipid interface within 8 ns and showed strong interfacial enrichment, with residence probabilities of 85% for nicotine and 73% for cotinine. Nicotine exhibited pronounced membrane permeability, repeatedly crossing the entire bilayer, whereas cotinine remained largely confined to the interfacial region. Free energy profiles revealed a favorable minimum for nicotine inside the bilayer (0.89 nm from the center) and a negative transfer free energy (−2 kcal/mol), while cotinine faced a substantial barrier with a positive transfer free energy of 2.5 kcal/mol. Orientational analyses showed broader angular distributions for nicotine, consistent with frequent conformational inversions, whereas cotinine displayed more restricted and stable interfacial orientations. Both molecules reduced lipid acyl-chain order parameters, altered membrane electrostatic potentials, and induced local membrane thinning from an average thickness of ∼3.82 nm. These results quantitatively demonstrate how subtle molecular differences control membrane affinity, permeability, and membrane perturbation, providing fundamental insight into alkaloid–membrane interactions and their potential biological implications.

Undergraduate laboratory and project-based learning (PBL) activities can be effective for skill development, yet they often lack sustained industry engagement and explicit structures that connect scientific reasoning with engineering-oriented decision making. This paper reports an Open Innovative Experiment model that integrates Science–Industry–Education collaboration into a course-level PBL framework for undergraduate training. Using polyimide films with tunable branching as a representative case study, students completed a structured workflow that combined laboratory preparation/characterization with simulation-assisted interpretation to examine how structure and testing configurations influence dielectric breakdown behavior. Implementation of the model through an industry-engaged, dual-mentor structure enabled authentic problem contexts and constraints while maintaining nonproprietary boundaries. Student and industry-partner feedback, together with course-level outcomes, indicated strengthened experimental competency, improved awareness of reliability/quality considerations, and enhanced ability to translate classroom knowledge into practice. The model provides a transferable approach for incorporating industry engagement into undergraduate experimental curricula in applied chemistry and related disciplines.