Rapid formation of regulated methacrylate networks yielding tough materials for lithography-based 3D printing

Multifunctional methacrylates are highly reactive monomers for radical photopolymerization, but yield brittle materials due to their inhomogeneous and highly crosslinked network architecture. Addition fragmentation chain transfer (AFCT) reagents serve as additives for the regulation of radical network formation and pave the way to photopolymer networks with high toughness. However, AFCT reagents (e.g. β-allyl sulfones) tend to have a negative influence on the reaction speed which limits them for lithographybased 3D fabrication. Vinyl sulfone esters are described as a new class of AFCT reagents for methacrylate-based photopolymerization without the drawback of retardation but good regulation of network architecture. The resulting materials show high network homogeneity, low shrinkage stress, and a significant increase in CvC double bond conversion and toughness. This promises great potential for vinyl sulfone esters as AFCT reagents in photopolymer applications. First 3D parts have been successfully fabricated via digital light processing.