Accelerated rupture at the liquid/liquid interface

A detailed investigation of a new process of dewetting which takes place at the liquid-liquid interface of partially miscible liquids is reported. We use nuclear reaction analysis and real-time video monitoring to examine in detail the formation of two coexisting liquid films formed by phase separation from a mixture and in particular the subsequent dewetting of one of them from the other. A dewetting front propagates from the edge of the spin-cast sample inward, and it is suggested that a Marangoni flow leads to its initiation and subsequent propagation via a mechanism involving fast rupture of holes ahead of the front. Subsequent growth of holes results in the coalescence of the surrounding rims and their breakup into droplets, whose persistent motion at the interfacial plane is described. This route of dewetting differs from the classical ones involving thermally driven fluctuations or nucleation of dewetting centers, by its relatively short induction time, the evolution of a front, and its unique morphological characteristics. The process is believed to be general and important in thin films of partially miscible liquid mixtures.