Dynamic monomers for hot lithography: the UPy motif as a versatile tool towards stress relaxation, reprocessability, and 3D printing

Abstract

Supramolecular polymers can substantially influence the dynamic mechanical properties in slightly crosslinked polymer networks. One prominent example of supramolecular building blocks is 2-ureido-4[1H]-pyrimidinones (UPy). Combining UPy-terminated supramolecular segments with classical covalent-reactive monomers implements dynamic behavior in photopolymerizable systems. In this work, a UPy-based methacrylic monomer (up to 20 mol%) was introduced in a classical photopolymerizable methacrylate matrix. The influence of the UPy-motif on the reactivity and (thermo)mechanical properties was investigated via RT-NIR photorheology, DMTA, and tensile testing. The dynamic behavior was characterized via stress relaxation and reprocessing studies to demonstrate the dynamic effects of photopolymers containing the UPy building block compared to difunctional photopolymers with similar structural features. In a final step, the UPy-based photopolymerizable system was applied in bulk in a Hot Lithography printing process at elevated temperatures yielding complex 3D-printed parts with high resolution and precision.