Conversion of waste poly(vinyl chloride) to branched polyethylene mediated by silylium ions

• Published in: Chemical science (Cambridge) Vol. 15; no. 23; pp. 8766 - 8774
• Main Authors: Wood, Zachary A, Castro, Eunice C, Nguyen, Angelyn N, Fieser, Megan E
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 12-06-2024; The Royal Society of Chemistry
• Subjects: Chemistry; Chlorine; Dechlorination; Melting points; Polyethylene; Polyethylenes; Polyvinyl chloride; Thermodynamic properties
• ISSN: 2041-6520; 2041-6539
• DOI: 10.1039/d4sc00130c

Full dechlorination of poly(vinyl chloride) (PVC) in a controlled manner to yield useful polymeric and chlorinated products is of great interest for the processing of PVC waste. Forming polyethylene (PE) without corrosive by-products would allow for a pre-treatment of PE wastes that are often contaminated with PVC. Herein, full dechlorination of PVC has been achieved
via
generation of silylium ions
in situ
, to furnish PE products. Complete dechlorination of PVC can be achieved in 2 hours, yielding organic polymer that has similar spectroscopic and thermal signatures of branched PE, with no observable chlorine. The degree of branching can be tuned between 31 and 57 branches per 1000 carbons, with melting temperatures ranging from 51 to 93 °C. This method is applicable to not only pure PVC, but also commercial PVC products. Depending on if the PVC products are separated from plasticizers, different melting points of the resulting PE are observed. PVC dechlorination in the presence of PE waste is also shown. This is the first report of being able to cleanly convert PVC waste to PE in high yields and tune the thermal properties of the PE product, highlighting the remarkable control that silylium ion mediated transformations enables compared to past chemical methods.
Lewis acidic silylium ions are used to completely remove Cl from poly(vinyl chloride) (PVC) in clean and commercial products through hydrodechlorination. Reaction conditions were found to impact the branching in the resulting polyethylene (PE).