(261b) Combined Surface Templating and in Situ phase Separation for Multi-Scale Chemical and Topographical Patterning

As revealed in numerous natural species (plants, insects, etc.), multi-scale, hierarchical surface structures impact interfacial properties including wettability and adhesive character. Furthermore, hierarchical patterning can also impart unique functionalities to interfaces including effective water/fog harvesting and controlled fluid transport. Unfortunately, current strategies to emulate these natural designs rely on procedures where patterning is limited to a single scale. Therefore, to achieve desired hierarchical structures, multiple processing steps are required for patterning on differing length scales (i.e., nano, micro, meso). This constitutes a major challenge with regards to feasibility and scale-up. To address this gap, here we describe how combined templating and phase separation during in situ network polymerizations can be leveraged to yield surface patterning on multiple length scales in a single polymerization procedure. Photopolymerizable resins consisting of a (co)polymer network modified with inert polymer additives (poly(methyl methacrylate), poly(styrene), etc.) were chosen for this study based on previous demonstrations of thermodynamically driven phase separation during photopolymerization. We first demonstrate how in situ phase separation of these resins results in unique surface topographies on the microscale, with features that are qualitatively different than expected classical wrinkling instabilities of polymer coatings exposed to oxygen during curing. To achieve additional length-scales of patterning, template materials (glass, stainless steel, etc.) were employed. The use of these templates induces large scale variations in surface energy that can be tailored via template choice and are ultimately characterized by wettability analysis at distinct locations on the polymer coating. We demonstrate how additional experimental parameters such as film thickness, template size, cross-link density, and external environment can be leveraged to modify and manipulate these features on multiple length scales. This platform has promise in emerging applications in composites and coatings, as simultaneous topographical and chemical patterning can be tailored from a single precursor resin and polymerization procedure.