The properties of polymer foams not only depend on the type of polymer but also on their cellular microstructure such as the pore size, the pore wall thickness and the interconnectivity between the pores. Scientists have gained some control over the microstructure of polymer foams by using emulsion templating for their generation. Especially high internal phase emulsions (HIPEs) are of great interest because they lead to low density polymer foams. To date most emulsions are generated via agitation, resulting in a highly polydisperse template the polymerization of which leads to highly polydisperse polymer foams. We recently showed that water-in-styrene HIPEs can also be generated with microfluidic lab-on-a-chip techniques, which, in turn, leads to monodisperse emulsions and thus to monodisperse polymer foams. We also showed that an initiation of the polymerization at the interface with the water soluble initiator potassium persulfate (KPS) always leads to polymer foams with a polyhedral closed-cell morphology and walls of homogeneous thickness. In the work at hand, we show how the pore wall thickness of cross-linked polystyrene foams can be fine-tuned without changing the pore size itself by varying parameters such as the surfactant concentration, the emulsion height and the initiation temperature<sup>5</sup>. Changing these parameters systematically one obtains pore wall thicknesses between 10 µm and 3 µm. The reduced pore wall thickness is directly reflected in the density and the mechanical stability of the polymer foams, opening a new arena for tailor-made materials.

Tuning the pore wall thickness of monodisperse polymer foams

252nd National Meeting (2016)

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