Employing Photosensitizers for Rapid Olefin Metathesis Additive Manufacturing of Poly(dicyclopentadiene)

The additive manufacturing (AM) of thermoset polymers has been limited primarily to radical or cationic photopolymerizations, restricting available resins and attainable material properties. Recent efforts in the AM of polydicyclopentadiene (pDCPD) via ring-opening metathesis polymerization (ROMP) have resulted in printable thermoset materials with advantageous high-performance properties. However, previous demonstrations of DCPD ROMP for AM have been hindered by sluggish printing rates and there is limited characterization of the printed materials. Here, we report the rapid direct-ink-write (DIW) AM of pDCPD by employing a photosensitizer/latent catalyst system to obtain unprecedented rates of photocatalyzed ROMP of DCPD (60 mm·s–1). Characterization of the resin system in situ shows that the use of a photosensitizer decreases the induction period from 78.3 to 3.6 s. The short induction period and rapid curing enable the DIW AM of geometrically complex architectures and printing without the need for supports. In addition, the living nature of ROMP and high catalyst stability is leveraged to improve the adhesion between layers, a long-standing and prevalent issue in extrusion-based AM. The system described herein can guide the development of rapid AM approaches for additional metathesis-active monomers and greatly expand the materials selection and performance properties achievable with additively manufactured thermoset resins.