Engineering degradable and recyclable thermosets is of paramount importance to achieving a sustainable future. However, there is often a tradeoff between the thermomechanical performance of thermoset materials and their ease of degradability. Imbuing degradability at the expense of thermomechanical performance can often be prohibitive, seriously hindering the rollout of environmentally-friendly alternative materials. For example, in the context of polydicyclopentadiene (pDCPD), the introduction of cleavable bonds into network strands can facilitate material degradation, but also lowers glass transition temperature (Tg). By contrast, the installation of cleavable crosslinkers could maintain, or potentially increase Tg, but such a strategy does not confer degradability. Here, we introduce a ‘strand-cleaving crosslinker’ (SCC) approach that simultaneously increases crosslink density and confers degradability to pDCPD through the incorporation of difunctional comonomers which introduce cleavable strands into the network backbones, but also crosslink. With this strategy, we can produce degradable pDCPD featuring a 58 °C higher Tg than previously reported analogous degradable pDCPD, and 5 °C higher than native pDCPD. Moreover, degradation can be achieved at as little as 10 volume % of SCC. A theoretical model corroborating these results is presented. These results suggest that SCCs could offer a generally applicable strategy for the design of degradable thermoset materials without compromise on thermomechanical performance.

Overcoming performance-degradability tradeoffs in thermosets through strand-cleaving crosslinkers

ACS Spring Meeting 2021

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