Controlled release of hydrophobic agents from salt-responsive capsules is hindered by the hydrophilic shell and interfacial tension between inner oil and surrounding water. Rupturing shells in salt solution is another effective way. However, the densely entangled polyelectrolytes (PEs) in shells determined that the rupture requires extremely high ion-strength. Herein, salt-responsive capsules with double-network shells including a continuous PE-nanocrystal network and interfacial ion pairs are proposed and revealed via a one-step interfacial multilevel and multicomponent assembly (IMMA) method. Rigid nanocrystals can weaken the entanglements of PE chains and reduce the critical salt-concentration. Interfacial ion pairs are responsible for maintaining the stability of the shells. Such double networks enable the disintegration of capsules in an applicable salt-concentration without damaging the stability of capsules. In addition, hydrophobic domains assemblied by surfactants and PE-nanocrystal network supply transport pathway for oil to across hydrophilic shells and subsequently produce inverse micelle to carry oil into water. The mechanism of formation and release of capsules is systematically investigated, which further demonstrates IMMA to be a typical method for creation of sophisticated structures in a brief way.
Keywords: double networks; emulsions; interfaces; multilevel assembly; polyelectrolyte complexes; salt-responsiveness.