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Abstract Hydrodechlorination of poly(vinyl chloride) (PVC) directly to polyethylene (PE) represents a way to repurpose PVC waste, while avoiding toxic and/or corrosive byproducts that are produced at the end of life of PVC items. Prior studies identified a rhodium‐catalyzed route to hydrodechlorinate PVC to form PE products with sodium formate as a hydrogen source. While all chlorine could be removed to form PE‐like polymers, the reaction was slow and side reactions introduced undesirable cross‐links in the polymer product. In this work, mechanistic studies are pursued to improve catalytic activity for this method. Xantphos and diphenylphosphinoethane (DPPE) both support Rh(I) to promote this reaction to full conversion, effectively removing all chlorine from PVC samples, with Xantphos support providing the fastest metal catalysis for hydrodechlorination to date. However, side reactions to form cross‐links are present for both catalyst systems. Control studies suggest the proposed route for cross‐link formation also deactivates the Rh catalyst, indicating the cross‐link formation can also be the cause for the reaction to slow over time. Other reaction conditions were found to influence the selectivity between hydrodechlorination and cross‐link formation. These results introduce key catalyst design principles to improve methods for hydrodechlorination of PVC, allowing for sustainable repurposing of this toxic polymer waste. 

Earth-abundant Ni-catalyzed poly(vinyl chloride) hydrodechlorination leads to a polyethylene like product with in-chain incorporation of carbonyl groups using sodium formate as a source of both H and CO, yielding NaCl as a benign co-product. 

Combined hydrodechlorination and Friedel–Crafts alkylation of poly(vinyl chloride) can contain secondary Friedel–Crafts alkylation reactions that modify thermal properties of products, depending on the arene substrate and reaction temperature. 

Reaction of poly(vinyl chloride) (PVC) with 5 equiv. of triethyl silane in THF, in the presence of in situ generated (xantphos)RhCl catalyst, results in partial reduction of PVC via hydrodechlorination to yield poly(vinyl chloride- co -ethylene). Increasing catalyst loading or using N , N -dimethylacetamide (DMA) as a solvent both diminished selectivity for hydrodechlorination, promoting competitive dehydrochlorination reactions. Reaction of PVC with 2 equiv. of sodium formate in THF in the presence of (xantphos)RhCl affords excellent selectivity for hydrodechlorination along with complete PVC dechlorination, yielding polyethylene-like polymers. Higher catalyst loadings were necessary to activate PVC towards reduction in this case. In contrast, reaction of PVC with 1 equiv. of NaH in DMA, in the presence of (xantphos)RhCl, exhibited good selectivity for dehydrochlorination, as well as much higher reaction rates. These results combined shed light on the interplay between critical reaction parameters that control PVC's mode of reactivity. 

Tandem hydrodechlorination/Friedel–Crafts alkylation of poly(vinyl chloride) (PVC) is achieved using silylium ion catalysts to prepare new styrenic copolymers of polyethylene. In many cases, conversion of PVC was complete within minutes, indicating facile means of PVC functionalization at low catalyst loadings.