Temperature Orthogonal Dynamic Polymer Networks

Abstract

Latent catalysts have gained increased attention for balancing high creep resistance with rapid (re)processability in covalent adaptable polymer networks (CANs). Among the reported systems, thermolatent catalysts offer particular advantages, as their activation is independent of part geometry, optical transparency, or irradiation depth, making them highly attractive for bulk materials and additively manufactured components. Here, a systematic study of thermobase generators (TBGs) with distinct activation and deactivation temperatures is presented, and their impact on bond-exchange-controlled stress relaxation in dynamic thiol–ene photopolymers undergoing transesterification is quantitatively assessed. Cyanoacetate- and oxalate-based TBGs, releasing amine bases at well-separated temperature windows, are investigated to directly correlate catalyst (de)activation with macroscopic flow behavior. Based on their non-overlapping thermal profiles, a cyanoacetate-based TBG releasing N,N,N′,N′-tetramethylguanidine and an oxalate-based TBG releasing 1,5,7-triazabicyclo[4.4.0]dec-5-ene are combined within a single CAN to realize temperature-orthogonal catalysis. Stress relaxation measurements demonstrate that the two catalysts operate independently and enable reversible, multi-cycle switching between four distinct bond-exchange regimes using temperature alone. This concept allows decoupling material stability under service conditions from rapid flow during reshaping, repair, or welding, and provides a versatile platform for applications requiring programmable mechanical response, such as soft robotic actuators, switchable adhesives or (re)processable additively manufactured components. As a proof of concept, multi-reshapable objects are fabricated via digital light processing 3D printing.