Non‐Classical Self‐Assembly of Anisotropic Magneto‐Organosilica Janus Particles Possessing Surfactant Properties and the Field‐Triggered Breakdown of Surface Activity and Amphiphilic Properties

Abstract Using colloidal particles as models to understand processes on a smaller scale is a precious approach. Compared to molecules, particles are less defined, but their architecture can be more complex and so is their long‐range interaction. One can observe phenomena that are unknown or much more difficult to realize on the molecular level. The current paper focuses on particle‐based surfactants and reports on numerous unexpected properties. The main goal is creating an amphiphilic system with responsiveness in surface activity and associated self‐organization phenomena depending on applying an external trigger, preferably a physical field. A key step is the creation of a Janus‐type particle characterized by two types of dipoles (electric and magnetic) which geometrically stand orthogonal to each other. In a field, one can control which contribution and direction dominate the interparticle interactions. As a result, one can drastically change the system's properties. The features of ferrite‐core organosilica‐shell particles with grain‐like morphology modified by click chemistry are studied in response to spatially isotropic and anisotropic triggers. A highly unusual aggregation–dissolution–reaggregation sequence w as discovered. Using a magnetic field, one can even switch off the amphiphilic properties and use this for the field‐triggered breaking of multiphase systems such as emulsions.