Hydrodynamic instability triggered during thin-film formation by interfacial polymerization

An exothermic reaction at an immiscible liquid-liquid interface is at the core of several industrial processes and can trigger hydrodynamic instability. Here, we study interfacial polymerization, where a thin film is formed, whose morphology is known to be altered by synthesis conditions, impacting its industrial performance. Particle tracking microscopy is used to quantify fluid motion as a proxy for hydrodynamic instability intensity. Results indicate that, upon increasing polymerization-rate, particle motion transitions from Brownian to directed and is attributed to interfacially driven instabilities; concurrently, film morphology turns from smooth to crumpled. These results provide important insight for improved control over film fabrication.