skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: Controlling selectivity for dechlorination of poly(vinyl chloride) with (xantphos)RhCl
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.  more » « less
Award ID(s):
2203756 2018740
PAR ID:
10463189
Author(s) / Creator(s):
; ; ; ;
Date Published:
Journal Name:
Materials Horizons
Volume:
10
Issue:
6
ISSN:
2051-6347
Page Range / eLocation ID:
2047 to 2052
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; (, ChemSusChem)
    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. 
    more » « less
  2. ; (, Journal of Materials Chemistry A)
    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. 
    more » « less
  3. ; ; ; ; ; ; ; ; (, Polymer Chemistry)
    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. 
    more » « less
  4. ; ; ; ; (, Polymer International)
    Abstract Managing water resources has become one of the most pressing concerns of scientists in both academia and industry. Broadening access to nontraditional water feedstocks, such as brackish water, seawater and wastewater, requires a robust pretreatment process to prolong the lifetime and improve the efficiency of reverse osmosis treatment processes. Herein, pretreatment membranes with tunable hydrophilic characteristics and mechanical properties were developed through a facile and scalable technique. Specifically, poly(vinyl alcohol) (PVA) and poly(vinyl chloride) (PVC) were electrospun at various PVA‐to‐PVC mass ratios and then crosslinked with a poly(ethylene glycol) diacid. Fiber diameters and morphologies were characterized using scanning electron microscopy (SEM); Fourier transform infrared spectroscopy and confocal fluorescence microscopy further confirmed the presence of both polymers. Moreover, a rigorous analysis to map the PVA/PVC concentration was established to accurately determine the relative concentrations of the two polymers on the co‐spun mat. The crosslinking reaction noted above tuned the membrane porosity from 500 to 80 nm, as seen using SEM, and the mechanical properties were probed using tensile testing. The data revealed that the PVC content controlled the mechanical strength; moreover, higher PVA contents were expected to increase water permeation by enhancing the hydrophilicity, but the higher degree of crosslinking in these materials actually reduced water permeation. This work introduces a facile, scalable route for the manufacture of pretreatment membranes with tunable porosity, mechanical properties and water permeation behavior. © 2021 Society of Industrial Chemistry. 
    more » « less
  5. ; ; ; ; ; ; ; ; (, Polymer Chemistry)
    null (Ed.)
    The stringent control over the polymerization of less activated monomers remains one major challenge for Reversible Deactivation Radical Polymerizations (RDRP), including Atom Transfer Radical Polymerization (ATRP). Electrochemically mediated ATRP ( e ATRP) of a gaseous monomer, vinyl chloride (VC), was successfully achieved for the first time using a stainless-steel 304 (SS304) electrochemical reactor equipped with a simplified electrochemical setup. Controlled polymerizations were confirmed by the good agreement between theoretical and measured molecular weights, as well as the relatively narrow molecular weight distributions. Preservation of chain-end fidelity was verified by chain extension experiments, yielding poly(vinyl chloride) (PVC) homopolymers, block and statistical copolymers. The possibility of synthesizing PVC by e ATRP is a promising alternative to afford cleaner (co)polymers, with low catalyst concentration. The metal body of the reactor was also successfully used as a cathode. The setup proposed in this contribution opens an avenue for the polymerization of other gaseous monomers. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email