Interplay between photopolymerization and phase separation kinetics in photopolymerization-induced phase separation for stereolithography

Photopolymerization-induced phase separation can serve as a useful strategy for fabricating 3D printed multiscale polymer structures in stereolithography (SLA), when the phase separation of segregation agents is triggered by the polymerization to convert the low molecular weight monomers into polymer networks. Several factors control the structure and dynamics of polymerization-induced phase separation for SLA 3D printing, such as resin composition, molecular weight of polymers as a phase separation agent, and UV curing kinetics of the photo-curable monomers. Real-time turbidity measurements have been carried out to measure UV light transmittance through a photo-curable sample of predetermined thickness have been employed as a main method to monitor the phase separation of poly(ethylene glycol) with different molecular weights in (meth)acrylate monomer mixtures. UV LED intensity in particular serves as a useful experimental handle to tune and control the polymerization kinetics in the phase separation process and resulting network morphology within the confined space of resin films gap, which is analogous to the slice thickness in SLA.