Here, we show that when polymers are deconstructed as solids in a reaction medium that swells the polymer, the rate of chain cleavage is accelerated beyond that for bond cleavage in small molecule analogues. Moreover, by tailoring the reactive medium to promote swelling via kosmotropic and chaotropic principles, we show that the initial rates of deconstruction can be accelerated by up to 90%.

Here, we show how to redesign cycloolefin resins for biorenewable circularity by addressing how bio-derived polar functionality influences ring strain, ring–chain equilibria, and likelihood for catalyst poisoning. These bio-based cycloolefin resins (bioCOR) are thermally and photochemically polymerizable, resulting in high-modulus thermosets with excellent thermal stability. Most notably, we found that the efficacy of thermoset deconstruction to the original crosslinker depended strongly on the ring-closing depolymerization catalyst.

Circular plastics thrive on the ability to chemically recycle polymers into reusable monomers, ideally closing the loop from manufacturing to end of life. Mechanisms for heterogeneous polymer deconstruction are complex, involving diffusion and transport of reagents to reactive sites in a material continuously undergoing chemical transformations. A deeper understanding of deconstruction phenomena would better inform the molecular basis of circularity in plastics. Here, we show how nuclear magnetic resonance (NMR) spectroscopy, relaxometry, and diffusometry enable monitoring of heterogeneous deconstruction of a model elastomer with acid-cleavable diketoenamine bonds. In chaotropic aqueous HBr, polydiketoenamine (PDK) deconstruction is fast, enabled by macro- and micro-scale swelling in early stages, which facilitates acid penetration and protonation of reaction sites deep within the polymer sample. We observe a previously unrecognized hydrogen-bond stabilized protonated amine intermediate that is persistent throughout deconstruction, and found a strong correlation of its reactivity with swelling and chain kinetics. In kosmotropic aqueous H2SO4, PDK deconstruction is notably slower. Swelling occurred at a more gradual pace, creating a porous polymer matrix, yet polymer chain mobility remained low. Most notably, the kosmotropic character of aqueous H2SO4 resulted in a reaction site that was comparably less active in advancing hydrolysis and deconstruction to shorter oligomer chains, instead trapping acid in matrix pores and modifying the activity of the reaction medium under confinement in the process.

Recent studies demonstrated that the amidation of polyethylenes creates a range of amide-containing materials with enhanced properties, but the effect of these functional groups on the microstructure of these new materials is not known. Here we employ solid-state nuclear magnetic resonance (NMR) techniques to analyze the microstructure of amide-modified polyethylenes. While a decrease in crystallinity was observed with increasing amounts of functionalization, we found by measuring the chain mobility of the crystalline, non-crystalline, and interphasial regions of the polyethylenes with NMR relaxation techniques that the grafted amidyl groups partition into the rigid amorphous fraction (RAF) between the crystalline and non-crystalline regions. The chemical specificity of these NMR experiments creates precise assessments of the location of functional groups within the materials. Together, these insights into the microstructure and morphology of amide-containing polyethylenes lay a foundation for a deeper understanding of the structure and properties of functional polyolefins.