ANALYSIS OF BIJEL SYSTEMS USING COARSE-GRAINED SIMULATIONS

Abstract

Bicontinuous interfacially jammed emulsion gels (bijels) are particle-stabilized liquidliquid systems with significant potential in reactive separation and biomanufacturing applications. In this work, coarse-grained simulations based on dissipative particle dynamics (DPD) are employed to investigate the behavior and transport of macromolecules across bijel-like interfaces. A computational framework is first developed and validated to model bijel nanoscale structure and macromolecular behavior, with particular emphasis on polymer conformation and transport properties. Sensitivity analyses are performed to quantify the influence of DPD parameters on structural descriptors such as the radius of gyration, and a regression-based machine learning model is constructed to predict macromolecular conformations. As a representative case, messenger ribonucleic acid (mRNA) is incorporated into the system, enabling direct comparisons with thermodynamic polymer theories and experimental trends. Interfacial partitioning is systematically investigated under dilute conditions as a function of solvent-affinity asymmetry. Results show that partitioning is primarily governed by configurational entropy differences, with open-chain conformations exhibiting stronger desorption tendencies. The interplay between entropic and enthalpic contributions is further explored in multi solvent systems, where the feasibility of mRNA desorption and encapsulation is shown to depend on the balance between favorable solvent interactions and entropy loss. These results are summarized through a regime map relating system conditions to encapsulation behavior. The role of transport and simulation fidelity is also examined. It is demonstrated that strong viscosity asymmetries in DPD simulations can induce artificial preferential partitioning due to enhanced stochastic forces required by the fluctuation–dissipation theorem, highlighting limitations of the method and providing guidance for mitigation strategies. Finally, polymer transport across particle-laden interfaces is analyzed. Polymer morphology, nanoparticle coverage, and chain length are shown to govern translocation mechanisms. Compact polymers are dominated by size-sieving effects, while open-chain polymers exhibit transport controlled by confinement free-energy penalties, void accessibility within the particle network, and segment-by-segment translocation. External driving forces significantly enhance transport in diffusion-limited regimes but have minimal impact when steric constraints dominate. Overall, this work provides a comprehensive coarse-grained description of macromolecular behavior in bijel systems, establishing connections between thermodynamics, transport phenomena, and simulation methodology, and offering insights for the design of particle-stabilized separation processes.