Porous SiOC microspheres obtained via photopolymerization-assisted solidification templating of emulsions

Abstract

Porous polysiloxane-derived SiOC microspheres were produced via photopolymerization-assisted solidification templating of preceramic polymer emulsions, demonstrated for four structure-directing solvents (cyclohexane, cyclooctane, l-menthol, camphene). Internal pore morphologies of microspheres correspond to those of the respective monolithic analogues. In addition to unidirectional solidification of emulsions, a novel method is introduced for selective solidification and photopolymerization of cyclooctane/polymer droplets within the liquid water phase, significantly improving process efficiency. Cryomicroscopy supported evaluation of solidification kinetics of oil/water phases. Stirring intensity was found to control microsphere size. For the stirred-tank setup, SiOC microspheres showed monomodal size distributions (d50 = 199 µm) and modal pore opening diameters of 5.2 µm. A proof-of-principle was delivered for implementation of this process in a continuous-flow solidification/photoreactor, providing a base for future upscaling. The open-porous SiOC microspheres are a promising materials concept for application in catalysis or adsorption.