Polyfunctional Acrylic Non-isocyanate Hydroxyurethanes as Photocurable Thermosets for 3D Printing

Liquid acrylic oligourethanes are components of photocurable thermoset resins for applications ranging from coatings to 3D printing technologies like stereolithography. Traditionally they are derived from isocyanates which are highly moisture sensitive and do not tolerate hydroxy groups. Herein we report on a versatile non-isocyanate route toward tailoring hydroxyurethane methacrylates (HUMA) and their oligomers for photo cross-linking and 3D printing. The key intermediate is (2-oxo-1,3-dioxolan-4-yl)methyl methacrylate, also referred to as methacrylated glycerol carbonate, obtained by the chemical fixation of carbon dioxide with glycidyl methacrylate. Upon aminolysis with di- and polyfunctional aliphatic amines, the ring-opening reaction of the cyclic carbonate group yields HUMA. No handling of isocyanates is required. The HUMA molecular architectures govern photo cure as well as thermal and mechanical properties. An alternative strategy toward molecular design of polyfunctional acrylics exploits chemical modification of the pendant hydroxy groups, e.g., by esterification with methacrylic acid anhydride. The resulting higher acrylate functionality accounts for improving Young's modulus from 3160 to 4200 MPa and increasing the glass transition temperature from 86 to 173 degrees C with respect to HUMA-based formulations.