Polymer Surfactants at the Mesoscale: Packaging Liquid Droplets with Ultrathin Sheets and Filaments

We describe the design of a polymer chemistry and materials platform to fabricate mesoscale polymer surfactant (MPS) structures, as ultrathin filaments and sheets, which exhibit tailored properties in fluids and at fluidic interfaces. By coupling functional polymers with light-triggered chemical transformations and photolithographic methods, these MPS structures were found to segregate to, and assemble at, the interface of oil-in-water droplets. Using cross-linkable, fluorescent polymers, our MPS preparation produced objects of predetermined shapes on Si/SiO2 substrates which, upon release from the substrate, adhered to droplet interfaces as extended appendages (for MPS filaments) or as ultrathin films that wrapped the entire droplet surface (for MPS sheets). With MPS structures, tailored droplet-based assemblies were realized by strategically varying both the volume ratios of the fluid phases and methods of release from the substrate. Overall, this study of static and dynamic mesoscale polymer surfactants produces a breadth of fluidic structures and interfacial configurations, including individually wrapped droplets, droplet-MPS networks, and droplets trapped in nonequilibrium shapes. These findings thus translate the fundamental science of polymer chemistry at interfaces to the mesoscale using functional, programmed structures.