Scalable Synthesis of Thermoresponsive Janus Nanoparticles via Electrostatic Regulation for On-Demand Emulsion and Foam Stabilization

This study presents an electrostatically regulated strategy for the scalable synthesis of temperature-switchable Janus nanoparticles (JNPs). By employing a Co 2+ -mediated intramolecular cross-linking method guided by electrostatic interactions, we achieved high-concentration (10–20 mg mL –1 ) fabrication of monodisperse PEG- b -cPAAc@Co 2+ - b -PNIPAM, effectively overcoming the low-yield limitations associated with conventional single-chain cross-linking techniques. As temperature-responsive solid surfactants, PEG- b -cPAAc@Co 2+ - b -PNIPAM Janus nanoparticles enhance the stability of both emulsions and foams at an increased temperature (50 °C) due to the increased hydrophobicity of PNIPAM chains, which promotes their adsorption at the interface and forms a densely packed interfacial film. Foam stabilization experiments demonstrated a 25-fold increase in half-life (16 min at 9 mg mL –1 at 50 °C) compared to surfactant-only systems. Conversely, cooling below the LCST triggers immediate demulsification and foam collapse due to the hydrophilization of PNIPAM. This study not only presents an electrostatic modulation-based cross-linking strategy for the mass production of functional JNPs but also highlights their great potential as intelligent stabilizers in applications such as petroleum recovery and responsive soft materials.