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Plastics offer innumerable societal benefits but simultaneously contribute to persistent environmental pollution, dominated by polyethylene (PE) and isotactic polypropylene (iPP). Melt blending and reformulating postconsumer PE andiPP into useful materials presents a promising recycling approach. However, such repurposed plastics are generally mechanically inferior due to an inability to efficiently separate polyolefins in mixed waste streams; phase separation of PE andiPP results in brittleness as a consequence of poor interfacial strength. Recently, we demonstrated that a small amount (1 wt%) of a poly(ethylene)-block-poly(ethyl ethylene-ran-ethylene)-block-poly(ethylene) (EXE) triblock copolymer, synthesized by low-cost anionic polymerization of 1,3-butadiene followed by solution hydrogenation, restores tensile toughness to levels equivalent to virgin polyolefins. Unfortunately, low-temperature solvent insolubility of EXE, driven by crystallization of the E blocks containing 1.5 ethyl branches per 100 backbone repeat units (EB), presents a challenge for industrial hydrogenation. Comparable toughness (ca. > 400% strain at break) was achieved in the present work with 1.5 ≤ EB ≤ 6.5, accompanied by reduced EXE crystallinity and dissolution in cyclohexane down to room temperature at the highest EB content. This remarkable toughening behavior is attributed to a synergy between chain entanglements between the E end blocks and semicrystalline PE homopolymer and formation of E block “crystal nodules” that prevent chain pullout, along with topological constraints between the X loops and semicrystallineiPP. Our findings overcome barriers to commercial production of EXE with existing industrial facilities, providing a cost-effective strategy for recycling PE andiPP. 

Abstract The Chemistry in the Arctic: Clouds, Halogens, and Aerosols (CHACHA) field project aimed to advance the understanding of coupled meteorological and chemical processes in the atmospheric boundary layer during the seasonal increase in sea ice fracturing in spring. CHACHA sought to understand the interactions between this changing snow-covered surface, surface-coupled clouds, sea spray aerosols, multiphase halogen chemistry, and impacts of emissions from oil and gas extraction on atmospheric chemistry. The project measured greenhouse gases, reactive gases, size-resolved aerosol number concentrations, cloud microphysical properties, and meteorological conditions in real time, while also collecting particles for offline analysis. Two instrumented aircraft were deployed: the Purdue University Airborne Laboratory for Atmospheric Research and the University of Wyoming King Air. Flights were conducted out of Utqiaġvik, Alaska, between 21 February and 16 April 2022, sampling air over snow-covered and newly frozen sea ice in the Beaufort and Chukchi Seas, over open leads, and over the snow-covered tundra of the North Slope of Alaska, including the oil and gas extraction region near Prudhoe Bay. Observations showed that reactive bromine gases generally peaked near the snow-covered surface and decayed rapidly within the lowest few hundred meters where ozone was depleted, with concentrations reduced by nitrogen oxides emitted from oil fields. Cloud microphysical measurements revealed that thin clouds over and downwind of leads grew in vertical extent after contact with open water. Results from dropsondes indicated that convective boundary layers developed over leads, with depths ranging from 250 to 850 m depending on the fetch.