Catalytic Chain Transfer in Crosslinking Photopolymerizations

Presented here is a detailed account of the development and implementation of macrocyclic cobaloxime complexes as sulfur-free, catalytic chain transfer agents (CTAs) in crosslinking photopolymerizations. Although much of this review is dedicated to understanding the fundamentals of catalytic chain transfer (CCT) in photopolymerizations, its impact on network topology and resultant mechanical properties, future goals of applying this technology to multimaterial 3D printing are also discussed. It is our long-term ambition for catalytic, sulfur-free CTAs to supplant existing consumptive, sulfur-based agents to provide new, unexplored, and not currently possible to fabricate photopolymeric materials with a specific eye towards application in dentistry, additive manufacturing, and responsive materials.1 Introduction2 History of Catalytic Chain Transfer (CCT)3 Understanding Catalyst Purity and Chain Transfer Activity4 Evidencing CCT in a Crosslinking Photopolymerization5 Comparing Cobalt(II)-Catalysts to Other Relevant CTAs6 Performance of Cobalt(II)-Catalysts in Commercial Resins7 Limitations of Approach and Looking Forward