of this method to common impurities in plas-
tic waste.
The ability to place diverse functionality onto
polyolefins through this universal approach
provides an opportunity to substitute current
high-value plastics, and create new ones, using
postconsumer waste as a starting material.
Polyolefin ionomers such as SURLYN are a
high-value class of thermoplastics toughened
by ionic cross-links, with applications ranging
from structural adhesives to ion-conducting
membranes ( 44 ). However, SURLYN is synthe-
sized through radical copolymerization of
acrylic acid and ethylene, which limits polymer
architecture to a highly branched micro-
structure, precludes use ofa-olefins as comon-
omers, and limits functional group identity
to a carboxylate. These limitations compromise
the potential strength, toughness, and trans-
port properties of the materials. There are
currently limited strategies to prepare poly-
olefin ionomers on materials made through
Ziegler-Natta or related catalytic approaches
(i.e., LLDPE or HDPE). Given the structural
fidelity and lack of long-chain branching of
our polyolefin functionalization approach,
we envisioned creating ionomers from poly-
olefins through late-stage functionalization.
The generality of the C–H functionalization
mediated by 1 enabled the development of
a 2-bromoethyl thiosulfonate radical trap-
ping reagent that installed a primary bromide
onto the polyolefin (P23;Fig.4A).Displace-
ment of the bromide by methyl imidazole
yielded imidazolium-functionalized LLDPE
(P24), which represents a formal copolyme-
rization ofa-olefins with an ion-containing
vinyl monomer. The ionomers had distinct
properties from the parent LLDPE, includ-
ing solubility in polar aprotic solvents, a de-
creased melting temperature, and enhanced
clarity (fig. S25). Introduction of the imida-
zolium to only 2 mol % of the repeat units
substantially changed the material from a
thermoplastic to a tough elastomer (Fig. 4B).
Although yield stress and the Young’s mod-
ulus (E) ofP24decreased compared with
the parent LLDPE, the strain at break (eB)
quadrupled and the stress at break (sB) more
than doubled, leading to an increase in the
tensile toughness (UT) of >550%. These ten-
sile properties compare favorably to a commer-
cial sample of Dow SURLYN, demonstrating
the marked effect that a small amount of tar-
geted functionalization can have on material
properties.
Collectively, the ability to produce an iono-
mer from a postconsumer waste stream with
functional equivalence to the thermomechan-
ical properties of a high-value commercial
material make this upcycled material a poten-
tially environmentally sustainable substitute
for polyolefin ionomers ( 45 ). The transla-
tional potential of this method was further
demonstrated through C–H functionalization
of PCPE in a twin-screw extruder, which is
the infrastructure used for processing plas-
tic waste. Reacting reagent 1 with a 5 mol %
2-bromoethyl thiosulfonate radical trapping
reagent, we procured 7 g of 1 mol % bromo-
ethylthiolated PCPE (P25; Fig. 4C). Reaction
of the extruded material with methyl imid-
azole afforded a large-scale synthesis of the
polyolefin ionomer. Although further reagent
developmentisrequiredtomakethismate-
rial an economically sustainable substitute,
this C–H functionalization platform enables
access to a library of polyolefin ionomers,
among other materials, from plastic waste.
These ionomers can be systematically studied
to assess the impact of ion identity, ion con-
tent, and polymer branching on polyolefin
properties and circularity, and could ulti-
mately contribute to a more sustainable plas-
tics economy.REFERENCES AND NOTES- J. F. Hartwig,J. Am. Chem. Soc. 138 ,2–24 (2016).
- H.M.L.Davies,J. Org. Chem. 84 , 12722– 12745
(2019). - M. C. White,Science 335 , 807–809 (2012).
- B.Hong,T.Luo,X.Lei,ACS Cent. Sci. 6 , 622– 635
(2020). - T. Cernak, K. D. Dykstra, S. Tyagarajan, P. Vachal, S. W. Krska,
Chem. Soc. Rev. 45 , 546–576 (2016). - D. E. MacArthur, D. Waughray, M. R. Stuchtey,“The new
plastics economy: Rethinking the future of plastics”(World
Economic Forum, 2016); https://www3.weforum.org/docs/
WEF_The_New_Plastics_Economy.pdf. - A. Rahimi, J. M. García,Nat. Rev. Chem. 1 , 0046
(2017). - A. E. Hamielec, P. E. Gloor, S. Zhu,Can. J. Chem. Eng. 69 ,
611 – 618 (1991). - J. B. Williamson, S. E. Lewis, R. R. Johnson 3rd, I. M. Manning,
F. A. Leibfarth,Angew. Chem. Int. Ed. 58 , 8654– 8668
(2019). - F.P.Brittet al.,“Report of the Basic Energy Sciences
Roundtable on Chemical Upcycling of Polymers”(Office of
Science and Technical Information, US Department of
Energy, 2019); https://www.osti.gov/biblio/1616517. - L. T. J. Korley, T. H. Epps 3rd, B. A. Helms, A. J. Ryan,Science
373 , 66–69 (2021). - Q. Anet al.,J. Am. Chem. Soc. 142 , 6216– 6226
(2020). - N. K. Boaen, M. A. Hillmyer,Chem. Soc. Rev. 34 , 267– 275
(2005). - D. Ravelli, M. Fagnoni, T. Fukuyama, T. Nishikawa, I. Ryu,ACS
Catal. 8 , 701–713 (2018). - M. C. White, J. Zhao,J. Am. Chem. Soc. 140 , 13988– 14009
(2018). - K. Liaoet al.,Nat. Chem. 10 , 1048–1055 (2018).
- Y. Kondoet al.,J. Am. Chem. Soc. 124 , 1164– 1165
(2002). - M. L. Lepageet al.,Science 366 , 875–878 (2019).
- S.-S. Geet al.,RSC Advances 8 , 29428– 29454
(2018). - D. C. Blakemoreet al.,Nat. Chem. 10 , 383– 394
(2018). - V. A. Schmidt, R. K. Quinn, A. T. Brusoe, E. J. Alexanian,J. Am.
Chem. Soc. 136 , 14389–14392 (2014). - R. K. Quinnet al.,J. Am. Chem. Soc. 138 , 696– 702
(2016). - W. L. Czaplyski, C. G. Na, E. J. Alexanian,J. Am. Chem. Soc.
138 , 13854–13857 (2016). - C. M. Plummeret al.,Polym. Chem. 9 , 1309– 1317
(2018). - J. B. Williamson, W. L. Czaplyski, E. J. Alexanian, F. A. Leibfarth,
Angew. Chem. Int. Ed. 57 , 6261–6265 (2018).
26. J. B. Williamsonet al.,J. Am. Chem. Soc. 141 , 12815– 12823
(2019).
27. A. Artaryanet al.,J. Org. Chem. 82 , 7093– 7100
(2017).
28. K. A. Margrey, W. L. Czaplyski, D. A. Nicewicz, E. J. Alexanian,
J. Am. Chem. Soc. 140 , 4213–4217 (2018).
29. H. Wuet al.,Angew. Chem. Int. Ed. 54 , 4070– 4074
(2015).
30. M. M. Tierney, S. Crespi, D. Ravelli, E. J. Alexanian,
J. Org. Chem. 84 , 12983–12991 (2019).
31. C. R. Pittset al.,J. Am. Chem. Soc. 136 , 9780– 9791
(2014).
32. R. D. Chamberset al.,J. Fluor. Chem. 129 , 811– 816
(2008).
33. H. Schönherr, T. Cernak,Angew. Chem. Int. Ed. 52 ,
12256 – 12267 (2013).
34. K. Fenget al.,Nature 580 , 621–627 (2020).
35. I. B. Perryet al.,Nature 560 , 70–75 (2018).
36. R. Oeschgeret al.,Science 368 , 736– 741
(2020).
37. C. Shu, A. Noble, V. K. Aggarwal,Nature 586 , 714– 719
(2020).
38. Y. Cheng, C. Mück-Lichtenfeld, A. Studer,Angew. Chem. Int. Ed.
57 , 16832–16836 (2018).
39. C. D. Matier, J. Schwaben, J. C. Peters, G. C. Fu,J. Am. Chem.
Soc. 139 , 17707–17710 (2017).
40. R. R. Merchantet al.,Science 360 , 75–80 (2018).
41. M. Häußler, M. Eck, D. Rothauer, S. Mecking,Nature 590 ,
423 – 427 (2021).
42. D. Liu, C. W. Bielawski,Polym. Int. 66 , 70– 76
(2017).
43. C. M. Plummer, L. Li, Y. Chen,Polym. Chem. 11 , 6862– 6872
(2020).
44.B.P.Grady,Polym. Eng. Sci. 48 , 1029– 1051
(2008).
45. C. Vadenbo, S. Hellweg, T. F. Astrup,J. Ind. Ecol. 21 ,
1078 – 1089 (2017).
ACKNOWLEDGMENTS
Funding:This work was supported by the National Institute of
General Medical Sciences (award no. R35 GM131708 to E.J.A.)
and the Air Force Office of Scientific Research (award no.
17RT0487 under the Young Investigator Program to F.A.L).
J.W.A. thanks the Henry G. Luce Foundation and the University
of North Carolina–Chapel Hill (UNC) for a Clare Boothe
Luce Graduate Student Fellowship and the UNC Chemistry
Department for the Venable Award. The UNC Department of
Chemistry’s Mass Spectrometry Core Laboratory provided
expertise and instrumentation that enabled this study with
support from the National Science Foundation (grant no.
CHE-1726291) and the National Institute of General Medical
Sciences of the National Institutes of Health (grant no.
R35GM118055). The UNC Department of Chemistry’s NMR
Core Laboratory provided expertise and instrumentation that
enabled this study with support from National Science
Foundation (grant nos. CHE-1828183 and CHE-0922858). We
thank the Dow Chemical Company for supplying samples of
SURLYN ionomers and HighCube or providing samples of
postindustrial and postconsumer plastic waste.Author
contributions:E.J.A. and F.A.L. conceived of the work. All
authors designed the experiments. T.J.F., J.W.A., E.K.N., and
A.S.M performed and analyzed the experiments. E.J.A., F.A.L.,
T.J.F., and J.W.A. prepared the manuscript.Competing
interests:E.J.A. and F.A.L. are inventors on US provisional
patent application 63/188,215 covering the diversification
of C–H bonds in small molecules and polyolefins, including the
upcycling of polymers, filed by UNC.Data and materials
availability:Experimental and characterization data are
available in the supplementary materials.SUPPLEMENTARY MATERIALS
science.org/doi/10.1126/science.abh4308
Materials and Methods
Figs. S1 to S18
Tables S1 to S3
References ( 46 – 77 )8 March 2021; resubmitted 10 August 2021
Accepted 20 December 2021
10.1126/science.abh4308550 4 FEBRUARY 2022•VOL 375 ISSUE 6580 science.orgSCIENCE
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