Temperature-Sensitive Janus Particles PEG/SiO₂/PNIPAM-PEA: Applications in Foam Stabilization and Defoaming

The current study presents a scalable approach for the preparation of temperature-responsive PEG/SiO₂/PNIPAM-PEA Janus particles and, for the first time, investigates their potential applications in stabilizing foam and defoaming by adjusting the temperature. The method utilizes a (W₁ + O)/W₂ emulsion system, which incorporates appropriate surfactants to stabilize the emulsion and prevent rapid dissolution of the hydrophilic triblock polymer PEG-b-PTEPM-b-PNIPAM in water. The PEG/SiO₂/PNIPAM-PEA Janus particles with temperature-responsive characteristics were synthesized in a single step that combined the sol-gel reaction and photoinduced free radical polymerization. The contact angle of the hydrophilic PEG/SiO₂/PNIPAM surface was measured to be 54.7 ± 0.1°, while the contact angle of the hydrophobic PEA surface was found to be 122.4 ± 0.1°. By incorporating PEG/SiO₂/PNIPAM-PEA Janus particles at a temperature of 25 °C, the foam's half-life is significantly prolonged from 42 s to nearly 30 min. However, with an increase in temperature to 50 °C, the foam's half-life rapidly diminished to only 44 s. This innovative application effectively enhances foam stabilization at low temperatures and facilitates the rapid dissipation of foam at high temperatures.