Cleavable Strand‐Fusing Cross‐Linkers as Additives for Chemically Deconstructable Thermosets with Preserved Thermomechanical Properties

Abstract

Permanently cross-linked polymer networks—thermosets—are often difficult to chemically deconstruct. Theinstallation of cleavable bonds into the strands of thermosets using cleavable comonomers as additives can facilitatethermoset deconstruction without replacement of permanent cross-links, but such monomers can lead to reducedthermomechanical properties and require high loadings to function effectively, motivating the design of new and optimalcleavable additives. Here, we introduce “strand-fusing cross-linkers” (SFCs), which fuse two network strands via a four-way cleavable cross-link. SFCs enable deconstruction of model polydicyclopentadiene (pDCPD) thermosets with aslittle as one-fifth of the molar loading needed to achieve deconstruction using traditional cleavable comonomers. SFCsfunction under traditional oven curing as well as low-energy frontal ring-opening metathesis polymerization (FROMP)conditions and lead to improved thermomechanical properties, for example, glass transition temperatures, compared toprior cleavable comonomer designs. This work motivates the development of increasingly improved cleavable additives toenable thermoset deconstruction without compromising material performance.