Deformation of Liquid-Liquid Phase Boundary as Template for Novel Surface Structured Polymer Particles and CoatingsPart of:
Biomineralizing organisms such as diatoms or radiolaria develop structures on the microscale, that owe their mechanical stability to special hierarchical architectures. The shaping of the inorganic material occurs through intricate biological molding processes which are to date difficult to mimic technically. One attempt to imitate those molding processes is to use dynamic liquid-liquid interfaces as templates.
In our research we focus on a biomimetic model system to create radiolaria-like structures, in which the deformation of an oil-water interface is used to shape microscopic, surface-structured particles. The deformation of the interface is induced by oppositely charged amphiphilic molecules that are introduced into the oil and water phase respectively. Conjunction and assembly of the different amphiphilic species at the phase boundary lead to the dynamic shaping of the interface. By introducing into the oil phase small amounts of monomeric metal oxide precursors which condense upon contact with water, Volkmer et al.  obtained complex-shaped mineralized hollow shells which comprise characteristic features of biological silicifying single cells.
In this work we show that the interfacial deformation can be retained at a desirable stage by replacing the oil with a polymerizable monomer and a radical initiator. Simultaneous polymerization of monomer droplets and deformation of the interface then produce rigid polymer particles with a diversified set of microstructures on their surface depending on the degree of polymerization. The deformation process is transferable to extended planes by dip-coating of a Polystyrene substrate with pre-polymerized monomer and immersing the substrate into an aqueous solution of the cationic surfactant obtaining a microstructured surface coating.
We present a simple and convenient way of producing polymer particles and coatings with bioinspired surface textures for potential use as additive for particulate composites, hydrophobic surfaces, or photocatalytic supports.
 D. Volkmer, S. Tugulu, M. Fricke, and T. Nielsen, “Morphosynthesis of Star-Shaped Titania-Silica Shells,” Angew. Chemie - Int. Ed., vol. 42, no. 1, pp. 58–61, 2003