Structural control of photo-curable polymer/silica NP nanocomposite by photo-polymerization induced phase separation under a confined film geometry

Polymerization-induced phase separation of nanoparticle additives in photo-initiated polymerization of monomers can serve as an effective strategy for fabricating novel 3D printed nanocomposite structures in stereolithography. For better dispersion of nanoparticles in the photo-curable monomers, the surface modification holds a key in controlling their compatibility with the monomers, and silica nanoparticles are ideally suited for its wide applicability of silica surface chemistry using silanes or polymer adsorption. We have compared the phase separation morphology difference of bare-silica and surface-functionalized silica nanoparticles in photo-curable (meth)acrylate monomers. Upon losing the compatibility of nanoparticles with the formation of highly crosslinked polymer networks, the repeated layer-by-layer photopolymerization for the polymerization-induced phase separation of silica nanoparticles allowed us to sequester the nanoparticles in less cross-linked regions. Optical and electron microscopy techniques are used to investigate the morphology, while the in-situ light transmission measurements have been utilized to have the real-time monitoring of the photopolymerization-induced phase separation.