Multistep Dynamic Wetting of Soy Protein Coacervates at Hydrophobic Interfaces

The wetting behavior of coacervates at hydrophobic interfaces not only emerges as a key phenomenon in cell biology, but also have a wide application in encapsulation technology. However, the wetting dynamics of coacervates at the hydrophobic interface that may govern their interfacial architectures and functionalities, is still poorly understood. Here, using soy glycinin as a model coacervate-forming protein, we explore the wetting behaviors of protein coacervates at the interface through multiple techniques. Glycinin coacervates diffuse into and wet the interface in forms of droplets, which further experience a multistep wetting progress. Coacervate droplets at the interface firstly undergo a steady growth due to the sequentially adsorbed counterparts from the bulk phase. Then, the adjacent coacervate droplets at the interface fuse into larger ones, and over the long time scales of evolution, the spreading of these larger coacervate droplets is observed. Modulation of solution pH to lower values enhances these wetting dynamics and drives the transition of interfacial coacervate membrane configuration from partial to complete wetting. Strong affinity of coacervates towards the interface and coacervate-coacervate interactions lead to the highly viscoelastic nature of interfacial coacervate membrane. These findings advance the understanding of the mechanism underlying coacervate wetting at hydrophobic interfaces.