Structural heterogeneity effects on microgel deswelling and interfacial properties: An extensive computational study

Abstract

Due to their structural heterogeneity, solvent-swollen microgels are endowed with a variety of useful properties and important applications. However, a comprehensive understanding of the structural heterogeneity effects on swelling pathways and interfacial properties is vital. Herein, the structural evolution of heterogeneous microgels (HMs) with different various swelling levels and ingredient volume ratios is studied using dissipative particle dynamics simulations combined with atomistic Monte Carlo. For yolk-shell microgels (YSMs), hydrophobic yolk chains with a strong deswelling state and low yolk/shell ingredient volume ratios tend to be directly exposed to solvent surroundings, resulting in anisotropic and inhomogeneous morphologies. Conversely, core-shell microgels (CSMs) possess hydrophobic core chains that are embedded within a water-swellable shell to raise mixing entropy; while Janus-shaped microgels (JSMs) exhibit reconfigurable morphologies between mushroom and dumbbell. In contrast to homogeneous microgels, which form a monolayer of adsorption at the oil/water interface, HMs form a double-layer pancake, orienting their hydrophilic and lipophilic domains toward the preferred liquid. Importantly, as increasing the spatial symmetry, the interfacial malleability of heterogeneous microgels is reinforced, resulting in thin interface thickness and low interfacial tension. The exceptional structural heterogeneity and nano-mechanochemical deformation of HMs dictate their interfacial properties, which should be highlighted during experimental fabrication.