Cleavable Comonomers Enable Degradable, Recyclable Thermoset Plastics

Thermosets play a key role in the modern plastics and rubber industries, comprising ~20% of polymeric materials with a worldwide annual production of ~65 million tons.(1,2) The high density of crosslinks that gives thermosets their useful properties (e.g., chemical/thermal resistance, and tensile strength) comes at the expense of degradability and recyclability. Here, using the industrial thermoset polydicyclopentadiene (pDCPD) as a model system, we show that when a small number of cleavable bonds are selectively installed within the strands of thermoset plastics, the resulting materials can display the same mechanical properties as the native material, yet they are able to undergo triggered degradation to yield soluble, recyclable products of controlled size and functionality. In contrast, installation of cleavable crosslinks, even at comparably high loadings, does not produce degradable materials. These findings reveal cleavable bond location as a design principle for controlled thermoset degradation. Moreover, a new class of recyclable thermosets poised for rapid deployment is introduced.