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In This Article

  • Summary
  • Abstract
  • Introduction
  • Protocol
  • Representative Results
  • Discussion
  • Acknowledgements
  • Materials
  • References
  • Reprints and Permissions

Summary

Here, we describe protocols for the preparation of trans-cyclobutane fused cyclooctenes (tCBCO), their polymerization to prepare depolymerizable olefinic polymers, and the depolymerization of these polymers under mild conditions. Additionally, protocols for the preparation of depolymerizable networks and compression molding of rigid linear plastics based on this system are described.

Abstract

The growing consumption of synthetic polymers and the accumulation of polymer waste have led to a pressing need for new routes to sustainable materials. Achieving a closed-loop polymer economy via chemical recycling to monomer (CRM) is one such promising route. Our group recently reported a new CRM system based on polymers prepared by ring-opening metathesis polymerization (ROMP) of trans-cyclobutane fused cyclooctene (tCBCO) monomers. This system offers several key advantages, including the ease of polymerization at ambient temperatures, quantitative depolymerization to monomers under mild conditions, and a broad range of functionalities and thermomechanical properties. Here, we outline detailed protocols for the preparation of tCBCO-based monomers and their corresponding polymers, including the preparation of elastic polymer networks and compression molding of linear thermoplastic polymers. We also outline the preparation of high ring strain E-alkene tCBCO monomers and their living polymerization. Finally, the procedures for the depolymerization of linear polymers and polymer networks are also demonstrated.

Introduction

The versatile and robust nature of synthetic polymers has made them a ubiquitous fixture of modern human existence. On the flip side, the same robust and environmentally resistant properties make polymer waste exceedingly persistent. This, together with the fact that a large fraction of all synthetic polymers ever made has ended up in landfills1, has raised legitimate concerns about their environmental effects2. Additionally, the open-loop nature of the traditional polymer economy has caused a steady consumption of petrochemical resources and a mounting carbon footprint3. Promising routes to a clo....

Protocol

NOTE: The protocols outlined below are detailed forms of experimental procedures reported previously15,18,19. Characterization of the small molecules and polymers has been reported previously15,18. Additionally, syntheses of monomers and polymers and depolymerization of polymers should be performed inside a fume hood with appropriate personal protective equipment (PPE), .......

Representative Results

Discussed here are representative results previously published15,18,19. Figure 5 shows the GPC traces for polymer P1 prepared by conventional ROMP with G2 (red curve)15 and living ROMP of EM1 with G1/PPh3 (black)18

Discussion

The tCBCO monomers can be prepared from a common precursor: the [2+2] photocycloadduct of maleic anhydride and 1,5-cyclooctadiene, anhydride 1. Since the crude anhydride 1 is difficult to purify but can be hydrolyzed readily, the crude photoreaction mixture is subjected to methanolysis conditions to yield the readily isolable methyl ester-acid 2. The recrystallization of 2 after column chromatography is key to obtaining the pure trans-c.......

Acknowledgements

We acknowledge funding support from the University of Akron and the National Science Foundation under grant DMR-2042494.

....

Materials

NameCompanyCatalog NumberComments
1 and 3 dram vialsVWR66011-041, 66011-100
1,4-butanediolSigma-Aldrich240559-100G
1,5-cyclooctadieneACROSAC297120010
1-butanolFisherA399-1
20 mL scintillation vialsVWR66022-081
Acetic AnhydrideAlfa-AesarAAL042950B
AcetoneFisherA18-20
Aluminum backed TLC platesSilicycleTLA-R10011B-323
Ammonium hydroxideFisherA669-212
AnilineTCIA0463500G
BD precisionglide (18 G)Fisher
ChloroformFisherC298-4
Column for circulation (to be packed with silver nitrate treated silica gel)Approximately 1 cm radius and 25 cm long, with inner thread on either end
d-ChloroformCambridge IsotopesDLM-7-100
DichloromethaneVWRBDH1113-19L
EDC.HCl; 3-(3-dimethylaminopropyl)-1-ethyl-carbodiimide hydrochlorideChemimpex00050
Ethyl AcetateFisherE145-20
Ethyl Vinyl EtherSigma-Aldrich422177-250ML
Glass chromatography columnsFabricated in-houseD = 20 mm, L= 450 mm and D = 40 mm, L = 450 mmThe columns are fitted with a teflon stopcock at one end and a 24/40 ground glass joint to accommodate a solvent reservoir if needed.
Grubbs Catalyst 1st Generation (M102)Sigma-Aldrich579726-1G
Grubbs Catalyst 2nd Generation (M204)Sigma-Aldrich569747-100MG
HexanesFisherH292-20
Hydraulic pressCarver Instruments#3912Coupled with temperature control modules (see below)
Hydrochloric acidFisherAA87617K4
Maleic AnhydrideACROSAC125240010
MethanolFisherA412-20
Micro essential Hydrion pH paper (1-13 pH)Fisher14-850-120
Normject Luer Lock syringes (1, 3 and 10 mL)VWR89174-491, 53547-014 and 53547-010
Photoreactor chamberRayonetRPR-100
QuadraPure TU (catalyst scavenger)Sigma-Aldrich655422-5G
Quartz tubesFavricated in-houseD=2", L=12.5" and D=1.5", L=10.5"
RotavapBuchi
SciLog Accu Digital Metering Pump MP- 40Parker500 mL capacity
Siliaflash Irregular Silica, F60SilicycleR10030B-25KG
Silver NitrateACROSAC197680050
Sodium hydroxideVWRBDH9292-2.5KG
Steel MoldFabricated in-houseOverall dimensions of mold cavity: length 20 mm, width 7 mm and depth 1 mm; gauge dimensions: length 10 mm, width 3 mm)
Steel PlatesFabricated in-house100 mm x 150 mm x 1 mm
Teflon Mold (6-cavities)Fabricated in-houseOverall cavity dimensions: length 25 mm, width 8.35 mm and depth 0.8 mm; gauge dimensions: length 5 mm, width 2 mm)
Teflon Sheets (0.005" thick)McMaster-Carr8569K61
Temperature Control ModulesOmegaC9000A and C9000°C units (two modules, one for top and one for bottom)
Triphenyl PhosphineTCIT0519500G
UV lampsRayonetRPR2537A and RPR3000A
Vacuum pumpWelch Duoseal
Whatman Filter Paper (grade 2)VWR09-810Ffilter paper

References

  1. Geyer, R., Jambeck, J. R., Law, K. L. Production, use, and fate of all plastics ever made. Science Advances. 3 (7), 1700782 (2017).
  2. Barnes, D. K. A., Galgani, F., Thompson, R. C., Barlaz, M. Accumulation and fragmentation of plas....

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