Vat photopolymerization of semicrystalline thermoplastics via photoinitiated ring opening metathesis polymerization

Vat photopolymerization (VP) is one of the most powerful tools today for the fabrication of complex materials. However, despite the variety of materials compatible with VP today, the fabrication of thermoplastics still remains a challenge. In this work, inspired by recent developments in photoinitiated ring-opening metathesis polymerization (photoROMP), we develop a photoROMP-compatible resin for the printing of semicrystalline poly(cyclooctene), and systematically explore their thermomechanical behavior. We show that crystallinity, and thus mechanical properties, evolve predictably as a function of thermal history, aging time, and light intensity during printing, enabling predictable tuning of stiffness and strength. Leveraging the contrast between amorphous and semicrystalline states, we further demonstrate thermally responsive architectures in which localized melting can be used to spatially modulate material stiffness on-demand, enabling programmable deformation. In addition, we highlight the robust shape memory behavior and excellent chemical stability of these printed pCOE materials. More broadly, this work demonstrates the ability of photoROMP to expand the material landscape of VP and underscores the potential utility of semicrystalline thermoplastics for the fabrication of adaptive 3D-printed structures.