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Temperature orthogonal dynamic polymer networks
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DOI：10.1039/D5SC10098D.png)
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Abstract
En 中文
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.
Keywords:
thermolatent catalysts
dynamic polymer networks
bond-exchange reactions
stress relaxation
temperature-orthogonal catalysis