The Polymer Society of Korea

Abstract

Aqueous two-phase systems (ATPS), formed by phase separation between polymer–polymer or polymer–salt aqueous solutions, are attracting increasing attention as sustainable and biocompatible platforms for separation and formulation technologies. Despite their advantages, the stability and performance of ATPS remain strongly influenced by interfacial phenomena, which are not yet fully understood. In this work, we investigate the dynamic behavior of colloidal particles confined at water–water interfaces, with particular emphasis on particle aggregation, structural evolution, and eventual detachment from the interface. By quantitatively evaluating the relative contributions of depletion interactions, capillary forces, van der Waals attractions, and electric double-layer interactions, we identify the dominant mechanisms governing particle behavior at different stages of interfacial evolution. Furthermore, we propose an image-based analysis of particle aggregates immediately prior to detachment as a new strategy for estimating interfacial tension in ATPS. This methodology is applicable to a broad range of particle sizes and densities, offering a general framework for elucidating colloidal interactions and interfacial mechanics in aqueous two-phase systems.