Photo-initiated Cu(I) azide alkyne cycloaddition (photo-CuAAC) polymer networks have been explored for a variety of applications, ranging from dental materials to membranes. The photo-CuAAC polymerization benefits from multiple synthetic advantages: spatial and temporal control over material formation, fast reaction kinetics, high conversion, and enhanced toughness. Reprocess-ability and heal-ability of damaged or aged thermosets can be achieved by incorporation of covalent dynamic bonds, which can allow for stress relaxation and flow of the material. By inserting monomers containing esters and hydroxyl pendant groups and amine centered crosslinkers into photo-CuAAC resins, stress relaxation is shown to occur in the cured networks by way of transesterification (TE) without the need for additional catalyst. The amine centered crosslinker provides the required catalytic activity for TE to occur and allows for stress relaxation and flow to occur within the network at elevated temperatures (T&gt;T<sub>g</sub>). The stress relaxation and flow behavior of the CuAAC vitrimer was tuned by varying the ratio of an amine centered to carbon centered alkyne crosslinker. The ability to reprocess and recycle high performance thermosets is a sought-after feature for the purpose of increasing material lifetime and sustainability.

Transesterification in photo-CuAAC networks via amine-centered crosslinkers

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