Foamed Styrene-in-Water Emulsions as Template for Highly Ordered Polystyrene Foams

The aim of this work was the synthesis and characterization of highly ordered, monodisperse polystyrene foams. The method of choice to achieve this aim was the combination of foamed emulsion templating and microfluidic foam production. First a concentrated styrene-in-water emulsion was foamed by means of microfluidics to produce a highly ordered, monodisperse liquid foam template which was then polymerized under VIS-light to obtain a solid polystyrene foam. This strategy allows specifically tuning the bubble size and liquid fraction of the template and consequently the pore size and density of the resulting polystyrene foam. By investigating the morphology of the polystyrene foams, we found that the pores are interconnected by windows - regardless of bubble size and liquid fraction of the template. The pore walls of the polystyrene foams were found to be porous, which is a direct result of the polymerization of the emulsion. The porous pore walls also influence the mechanical properties of the polystyrene foam. While the relation between the relative density and the Young's modulus and shear modulus, respectively, were found to be the same as described by various models, the actual values of the moduli were found to be smaller. The factor by which the moduli are lower is directly connected to the additional porosity and the models were altered accordingly.