Martin Selin
Date: 8 April 2025
Time: 17:40
Place: Center for Interdisciplinary Research, Bielefeld University, Germany
Colloidal particles typically require salt to overcome electrostatic barriers and adsorb to liquid-liquid interfaces. Here, we show that coating particles with polymers enables spontaneous adsorption without salt. Our model system consists of silica cores coated with poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA). Using optical tweezers, we track individual particles showing that the polymer shell makes particles jump into a dodecane–water interface. This behavior extends to other polymers. By tuning pH, we control polymer swelling and adsorption distance. At very low pH, the attachment to the interface is weak enough that the optical tweezers can pull particles out from the interface. During this desorption process we observe single polymers detaching. These findings offer new approaches for designing responsive emulsions.