Effect of spatial dimensionality on the interplay between spinodal decomposition and wetting in multicomponent mixtures

Abstract

We utilize mesoscale Cahn–Hilliard-based phase-field simulations to explore the effects of spatial dimensionality on wetting-influenced phase separation in binary and ternary mixtures. A comparison of simulations for similar model mixtures in two (2D) and three dimensions (3D) reveals a strong influence of dimensionality on domain morphology, topology, and the relative rate of coarsening. We examine near critical and far off-critical compositions and surface-directed spinodal decomposition induced by the presence of fixed filler particles. Familiar bicontinuous or droplet morphologies are observed in binary mixtures, depending on relative composition and quench depth, while ternary mixtures produce a much wider range of morphologies, such as lattices, worm-like structures, and patchy droplet spherical domains. Dimensionality can evidently play a key role, one effect being that droplet domains in 2D are often replaced by percolating network structures in 3D, even for the minority phases. Wetting effects introduce further complexity into phase separation dynamics, as evidenced by the formation of transient target patterns in 2D and long-lived onion-like structures around particles in 3D. Particle arrangement and concentration can also influence the wetting layer dynamics, leading to tubular domain structures and wetting-induced transitions from tubular to network morphologies. Finally, 3D systems generally exhibit more efficient droplet ripening and slower coarsening of the bicontinuous network compared to 2D. These findings provide qualitative insights into phase separation morphologies in multiphase systems, which may guide the design of blends with tailored mechanical, electrical, and transport properties.