Porous elastomers possessing gradient morphology or chemistry are highly desirable in applications including biomaterial interfaces, additive manufacturing, and as separation membranes. However, elastomers with a porosity gradient are difficult to prepare, often requiring slow multistep synthesis techniques or layer-by-layer lamination approaches. In this work we will demonstrate the synthesis of gradient porosity PDMS-based polymerized high internal phase emulsions (polyHIPEs) using a one-step macromolecular thiol-ene technique. Gradient porosity polyHIPEs with defined interfaces were prepared by patterning two or more emulsion formulations together before polymerization. Total porosity, pore size, and surface area could be tuned by varying the volume of aqueous dispersed phase in the emulsion. Total porosity values dictate the storage moduli of the polyHIPEs, where highly porous materials possess the lowest moduli of ~70-90 kPa. Tensile testing shows that the interface between two layers is mechanically robust and does not split during elongation at break experiments. This work provides an example of a simple technique to prepare gradient porosity PDMS-based polyHIPEs having up to five tunable porosity layers with strong interfaces.

Coupling thiol-ene chemistry and simple emulsion patterning can produce gradient porosity PDMS polyHIPEs

ACS Fall 2021

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