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.