Latent Catalysis as a Platform for Accessing Diverse Material Properties in Vat Photopolymerization 3D Printing.

Vat photopolymerization (VP) 3D printing is an attractive strategy to manufacture customized polymer parts. The properties of printed materials are limited by the need to employ a low viscosity liquid resin and achieve rapid polymerization kinetics. To circumvent this limitation, dual-cure methods have been developed using reagents embedded in the liquid resin formulation; however, the reagent-based approach requires the discovery and optimization of new chemistry for each desired material. Here, we demonstrate a catalytic, dual-cure platform that enables access to both Nylon-6 and polyester interpenetrating networks through VP 3D printing under a universal approach. Structure-reactivity relationships of the latent NHC catalysts led to the identification of a magnesium chloride-NHC adduct as a latent catalyst that is orthogonal to radical polymerization and can be unmasked at elevated temperatures post-printing to initiate ring-opening polymerization of lactones and lactams. This strategy results in access to semicrystalline materials, which are a challenging morphology to access via VP 3D printing, that have attractive mechanical properties and can be printed at high resolution. This work represents the first photochemical-based 3D printing of Nylon-based materials and demonstrates the value of catalytic approaches to access new material properties in VP 3D printing.