The Polymer Society of Korea

Abstract

Polymer-induced aqueous two-phase systems (ATPSs) provide a fully aqueous and biocompatible platform for soft materials but are often limited by poor interfacial stability. Here, we establish a unified framework in which interfacial stability in ATPSs enables structural connectivity and functional performance in all-aqueous materials. We show that depletion-induced aggregation of colloidal particles at water–water interfaces underlies the poor stability of conventional water-in-water (W/W) emulsions. Suppressing this aggregation allows stable particle adsorption and the formation of water-in-water high internal phase emulsions(W/W HIPEs) with ultrathin continuous phases, which can be photopolymerized to yield processable all-aqueous gels with tunable connectivity. The same principles extend to functional formulations, as demonstrated by oil-free sunscreens exhibiting uniform particle distribution, improved film formation, and enhanced UV protection compared to aqueous suspension.