A Comonomer Strategy for Triggered Degradation and Re/Upcycling of High-Performance Thermoset Plastics

Abstract

Thermosets play a key role in the modern plastics and rubber industries, comprising ~18% of polymeric materials with a worldwide annual production of 65 million tons. The high density of crosslinks that give these materials their useful properties comes at the expense of facile degradability and re/upcyclability. Here, using the high-performance industrial thermoset plastic poly-dicyclopentadiene (pDCPD) as a model system, we show that when a small number of cleavable bonds are selectively installed within the strands of thermoset plastics using a low-cost comonomer approach, the resulting materials display the same exceptional properties as the native material yet they can undergo triggered degradation to yield soluble, re/upcyclable products of controlled size and functionality. In contrast, installation of cleavable crosslinks, even at comparably high loadings, does not produce degradable materials. These findings shed new light on the topology of polymer networks, revealing cleavable bond location as a universal design principle for controlled thermoset degradation and re/upcycling.<br>

Molecularly Designed Additives for Chemically Deconstructable Thermosets without Compromised Thermomechanical Properties

“…Degradation of CyMeSi-based thermosets also occurred at 10% v/v, consistent with our previous findings using analogous 8-membered ring silyl ether comonomers (Figures 2B and S11−S13). 19 At higher loadings, the dissolution of NbMeSi-doped thermosets slowed, with 20, 33, 50, and 100% v/v samples mostly or partially dissolving at TBAF exposure times as long as 1 week. By contrast, CyMeSibased materials dissolved quickly at all loadings greater than 5% v/v.…”

“…Recently, we demonstrated that incorporation of ∼10% v/v of cleavable silyl-ether-based comonomer additives into pDCPD enables its chemical deconstruction into reusable oligomeric fragments without impacting many properties of virgin pDCPD such as Young's modulus, % strain at break, toughness, thermal stability, and ballistic impact response (Figure 1B). 19 Nevertheless, the introduction of conforma-tionally flexible comonomers resulted in significant, dosedependent decreases in T g as estimated through the peak of the tan(δ) curve from dynamic mechanical analysis (DMA) (up to 28 °C at 10% v/v). Others have reported similar T g depression when pDCPD is formed in the presence of comonomers rather than crosslinkers.…”

“…24−26 The addition of cleavable crosslinks to thermosets with permanent, noncleavable crosslinks, however, cannot facilitate chemical deconstruction into soluble products (Figure 1C). 19 Thus, additives that simultaneously enable thermoset deconstruction without compromising mechanical properties are elusive.…”

Polymer Networks: From Plastics and Gels to Porous Frameworks

“…The development of new reaction methodologies and advanced (macro)molecular architectures and topologies will further fuel the design of polymer networks with fascinating behaviors and improved mechanical properties. In addition, practical, scalable synthetic strategies are necessary to meet the existential need for sustainable polymer networks, next‐generation energy storage/harvesting materials, separations membranes, and catalysts. Finally, new tools for the generation of polymer network databases amenable to advanced computational screening and machine learning are highly sought after .…”

Polymernetzwerke: Von Kunststoffen und Gelen zu porösen Gerüsten

“…Die Entwicklung neuer Reaktionsmethoden und hochentwickelter (makro)molekularer Architekturen und Topologien wird die Erschließung von Polymernetzwerken mit faszinierendem Verhalten und verbesserten mechanischen Eigenschaften weiter vorantreiben. Außerdem sind geeignete, skalierbare Synthesemethoden erforderlich, um den existenziellen Bedarf an nachhaltigen Polymernetzwerken, Materialien für die Energiespeicherung bzw. Energieernte, Trennmembranen und Katalysatoren zu decken.…”