Stereolithographic 3D Printing Beyond Radical Photopolymerization

Abstract

Photopolymerization is a convenient curing technique for 3D printing soft matter materials with light (stereolithography, SL). While resin variability in SL allows for some flexibility of material properties, this flexibility is considerably restricted by a narrow process window. Most critically, formulation viscosities must remain low and curing times until the resin becomes solid (gel point) should be fast. Therefore, SL has traditionally been confined to the use of radical photopolymerization. Recent engineering developments, however, have enlarged this processing window, which creates an avenue towards utilization of radical-free polymerization mechanisms. For example, by increasing the printing temperature we were able to produce printed parts via ionic photopolymerization, which would typically be too slow for SL at room temperature. This unlocks entirely new polymer classes such as aliphatic polyester and polycarbonate networks with near-zero shrinkage for the first time.