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

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), ...

<ol>
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X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Completely+recyclable+biopolymers+with+linear+and+cyclic+topologies+via+ring-opening+polymerization+of+&#947;-butyrolactone.">Completely recyclable biopolymers with linear and cyclic topologies via ring-opening polymerization of &#947;-butyrolactone.</a> Nature Chemistry. 8 (1), 42-49 (2016).</li><li>Shi, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Design+principles+for+intrinsically+circular+polymers+with+tunable+properties.">Design principles for intrinsically circular polymers with tunable properties.</a> Chem. 7 (11), 2896-2912 (2021).</li><li>Neary, W. J., Kennemur, J. 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H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synthesis+and+characterization+of+stereoregular+ethylene-vinyl+alcohol+copolymers+made+by+ring-opening+metathesis+polymerization.">Synthesis and characterization of stereoregular ethylene-vinyl alcohol copolymers made by ring-opening metathesis polymerization.</a> Macromolecules. 38 (22), 9009-9014 (2005).</li><li>You, W., Hugar, K. M., Coates, G. 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G., Wang, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Overcoming+the+low+driving+force+in+forming+depolymerizable+polymers+through+monomer+isomerization.">Overcoming the low driving force in forming depolymerizable polymers through monomer isomerization.</a> Angewandte Chemie International Edition. 60 (48), 25493-25498 (2021).</li><li>Sathe, D., Chen, H., Wang, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Regulating+the+thermodynamics+and+thermal+properties+of+depolymerizable+polycyclooctenes+through+substituent+effects.">Regulating the thermodynamics and thermal properties of depolymerizable polycyclooctenes through substituent effects.</a> Macromolecular Rapid Communications. , (2022).</li><li>Vogel, A. I., Furniss, B. 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J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanism+of+hydration+of+simple+olefins+in+aqueous+solution.+cis-+and+trans-Cyclooctene.">Mechanism of hydration of simple olefins in aqueous solution. cis- and trans-Cyclooctene.</a> Journal of the American Chemical Society. 107 (22), 6363-6367 (1985).</li><li>Fang, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Studies+on+the+stability+and+stabilization+of+trans-cyclooctenes+through+radical+inhibition+and+silver+(I)+metal+complexation.">Studies on the stability and stabilization of trans-cyclooctenes through radical inhibition and silver (I) metal complexation.</a> Tetrahedron. 75 (32), 4307-4317 (2019).</li></ol>

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...

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 closed-loop polymer economy are, thus, highly sought after.
Chemical recycling to monomer (CRM) is one such route. The advantage of CRM over traditional recycling is that it leads to the regeneration of monomers that can be used to manufacture pristine polymers, as opposed to mechanical recycling of materials with deteriorating properties over multiple processing cycles. Polymers based on ring-opening polymerizations have appeared as especially attractive routes to CRM materials4. The thermodynamics of polymerization is typically an interplay between two opposing factors: the enthalpy of polymerization (&#916;Hp, which is typically negative and favors polymerization) and the entropy of polymerization (&#916;Sp, which is also typically negative but disfavors polymerization), with the ceiling temperature (Tc)&#160;being the temperature at which these two factors balance each other out5. For a polymer to be capable of CRM under practical and economically beneficial conditions, the right balance of &#916;Hp and &#916;Sp must be achieved. Cyclic monomers allow a convenient means to tune these factors via the selection of the appropriate ring size and geometry, since here, &#916;Hp is primarily determined by the ring strain of the cyclic monomers4,5. As a result, CRM polymers with a wide variety of monomers have been reported of late6,7,8,9,10,11. Out of these systems, ROMP polymers prepared from cyclopentenes are particularly promising due to the rather cheap starting material required and the hydrolytic and thermal stability of the polymers. Additionally, in the absence of a metathesis catalyst, the depolymerization is kinetically unfeasible, affording high thermal stability despite a low Tc12. However, cyclopentenes (and other monomers based on small cyclic structures) pose a key challenge-they cannot be readily functionalized, as the presence of functional groups on the backbone can affect the thermodynamics of polymerization in drastic, and sometimes unpredictable, ways13,14.
Recently, we reported a system that overcomes some of these challenges15. Inspired by examples of low-strain fused ring cyclooctenes in the literature16,17, a new CRM system was designed based on ROMP polymers of trans-cyclobutane fused cyclooctenes (tCBCO) (Figure 1A). The tCBCO monomers could be prepared at a gram scale from the [2+2] photo cycloadduct of maleic anhydride and 1,5-cyclooctadiene, which could be readily functionalized to achieve a diverse set of substituents (Figure 1B). The resulting monomers had ring strains comparable to cyclopentene (~5 kcal&#183;mol&#8722;1, as calculated using DFT). Thermodynamic studies revealed a low &#916;Hp (&#8722;1.7 kcal&#183;mol&#8722;1 to &#8722;2.8 kcal&#183;mol&#8722;1), which was offset by a low &#916;Sp (&#8722;3.6 kcal&#183;mol&#8722;1&#183;K&#8722;1 to &#8722;4.9 kcal&#183;mol&#8722;1&#183;K&#8722;1), allowing the preparation of high molecular weight polymers (at high monomer concentrations) and near quantitative depolymerization (&#62;90%, under dilute conditions) at ambient temperatures in the presence of Grubbs II catalyst (G2). It was also demonstrated that materials with diverse thermomechanical properties could be obtained while preserving the ease of polymerization/depolymerization. This ability was further exploited to prepare a soft elastomeric network (which could also be readily depolymerized), as well as a rigid thermoplastic (with tensile properties comparable to polystyrene).
One drawback with this system was the need for high monomer concentrations to access high molecular weight polymers. At the same time, due to extensive chain transfer and cyclization reactions, the polymerization was uncontrolled in nature. This was addressed in a subsequent work via photochemical isomerization of the Z-alkene in the tCBCO monomers to prepare highly strained E-alkene tCBCO monomers18. These monomers could be rapidly polymerized in a living manner at low initial monomer concentrations (&#8805;25 mM) in the presence of Grubbs I catalyst (G1) and excess triphenylphosphine (PPh3). The polymers could then be depolymerized to yield the Z-alkene form of the monomers. This has created opportunities to access new depolymerizable polymer architectures, including block copolymers and graft/bottlebrush copolymers.
In this work, detailed protocols are outlined for the synthesis of tCBCO monomers with different functional groups and their polymerization, as well as the depolymerization of the resulting polymers. Additionally, protocols for the preparation of dogbone samples of a soft elastomeric network and their depolymerization, as well as compression molding of the N-phenylimide substituted rigid thermoplastic polymer, are also described. Finally, protocols for the photoisomerization of a tCBCO monomer to its strained E-alkene tCBCO form and its subsequent living ROMP are also discussed.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>1 and 3 dram vials</td>
			<td>VWR</td>
			<td>66011-041, 66011-100</td>
			<td></td>
		</tr>
		<tr>
			<td>1,4-butanediol</td>
			<td>Sigma-Aldrich</td>
			<td>240559-100G</td>
			<td></td>
		</tr>
		<tr>
			<td>1,5-cyclooctadiene</td>
			<td>ACROS</td>
			<td>AC297120010</td>
			<td></td>
		</tr>
		<tr>
			<td>1-butanol</td>
			<td>Fisher</td>
			<td>A399-1</td>
			<td></td>
		</tr>
		<tr>
			<td>20 mL scintillation vials</td>
			<td>VWR</td>
			<td>66022-081</td>
			<td></td>
		</tr>
		<tr>
			<td>Acetic Anhydride</td>
			<td>Alfa-Aesar</td>
			<td>AAL042950B</td>
			<td></td>
		</tr>
		<tr>
			<td>Acetone</td>
			<td>Fisher</td>
			<td>A18-20</td>
			<td></td>
		</tr>
		<tr>
			<td>Aluminum backed TLC plates</td>
			<td>Silicycle</td>
			<td>TLA-R10011B-323</td>
			<td></td>
		</tr>
		<tr>
			<td>Ammonium hydroxide</td>
			<td>Fisher</td>
			<td>A669-212</td>
			<td></td>
		</tr>
		<tr>
			<td>Aniline</td>
			<td>TCI</td>
			<td>A0463500G</td>
			<td></td>
		</tr>
		<tr>
			<td>BD precisionglide (18 G)</td>
			<td>Fisher</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Chloroform</td>
			<td>Fisher</td>
			<td>C298-4</td>
			<td></td>
		</tr>
		<tr>
			<td>Column for circulation (to be packed with silver nitrate treated silica gel)</td>
			<td></td>
			<td></td>
			<td>Approximately 1 cm radius and 25 cm long, with inner thread on either end</td>
		</tr>
		<tr>
			<td>d-Chloroform</td>
			<td>Cambridge Isotopes</td>
			<td>DLM-7-100</td>
			<td></td>
		</tr>
		<tr>
			<td>Dichloromethane</td>
			<td>VWR</td>
			<td>BDH1113-19L</td>
			<td></td>
		</tr>
		<tr>
			<td>EDC.HCl; 3-(3-dimethylaminopropyl)-1-ethyl-carbodiimide hydrochloride</td>
			<td>Chemimpex</td>
			<td>00050</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethyl Acetate</td>
			<td>Fisher</td>
			<td>E145-20</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethyl Vinyl Ether</td>
			<td>Sigma-Aldrich</td>
			<td>422177-250ML</td>
			<td></td>
		</tr>
		<tr>
			<td>Glass chromatography columns</td>
			<td>Fabricated in-house</td>
			<td>D = 20 mm, L= 450 mm and D = 40 mm, L = 450 mm</td>
			<td>The columns are fitted with a teflon stopcock at one end and a 24/40 ground glass joint to accommodate a solvent reservoir if needed.</td>
		</tr>
		<tr>
			<td>Grubbs Catalyst 1st Generation (M102)</td>
			<td>Sigma-Aldrich</td>
			<td>579726-1G</td>
			<td></td>
		</tr>
		<tr>
			<td>Grubbs Catalyst 2nd Generation (M204)</td>
			<td>Sigma-Aldrich</td>
			<td>569747-100MG</td>
			<td></td>
		</tr>
		<tr>
			<td>Hexanes</td>
			<td>Fisher</td>
			<td>H292-20</td>
			<td></td>
		</tr>
		<tr>
			<td>Hydraulic press</td>
			<td>Carver Instruments</td>
			<td>#3912</td>
			<td>Coupled with temperature control modules (see below)</td>
		</tr>
		<tr>
			<td>Hydrochloric acid</td>
			<td>Fisher</td>
			<td>AA87617K4</td>
			<td></td>
		</tr>
		<tr>
			<td>Maleic Anhydride</td>
			<td>ACROS</td>
			<td>AC125240010</td>
			<td></td>
		</tr>
		<tr>
			<td>Methanol</td>
			<td>Fisher</td>
			<td>A412-20</td>
			<td></td>
		</tr>
		<tr>
			<td>Micro essential Hydrion pH paper (1-13 pH)</td>
			<td>Fisher</td>
			<td>14-850-120</td>
			<td></td>
		</tr>
		<tr>
			<td>Normject Luer Lock syringes (1, 3 and 10 mL)</td>
			<td>VWR</td>
			<td>89174-491, 53547-014 and 53547-010</td>
			<td></td>
		</tr>
		<tr>
			<td>Photoreactor chamber</td>
			<td>Rayonet</td>
			<td>RPR-100</td>
			<td></td>
		</tr>
		<tr>
			<td>QuadraPure TU (catalyst scavenger)</td>
			<td>Sigma-Aldrich</td>
			<td>655422-5G</td>
			<td></td>
		</tr>
		<tr>
			<td>Quartz tubes</td>
			<td>Favricated in-house</td>
			<td>D=2&#34;, L=12.5&#34; and D=1.5&#34;, L=10.5&#34;</td>
			<td></td>
		</tr>
		<tr>
			<td>Rotavap</td>
			<td>Buchi</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>SciLog Accu Digital Metering Pump MP- 40</td>
			<td>Parker</td>
			<td></td>
			<td>500 mL capacity</td>
		</tr>
		<tr>
			<td>Siliaflash Irregular Silica, F60</td>
			<td>Silicycle</td>
			<td>R10030B-25KG</td>
			<td></td>
		</tr>
		<tr>
			<td>Silver Nitrate</td>
			<td>ACROS</td>
			<td>AC197680050</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium hydroxide</td>
			<td>VWR</td>
			<td>BDH9292-2.5KG</td>
			<td></td>
		</tr>
		<tr>
			<td>Steel Mold</td>
			<td>Fabricated in-house</td>
			<td>Overall dimensions of mold cavity: length 20 mm, width 7 mm and depth 1 mm; gauge dimensions: length 10 mm, width 3 mm)</td>
			<td></td>
		</tr>
		<tr>
			<td>Steel Plates</td>
			<td>Fabricated in-house</td>
			<td>100 mm x 150 mm x 1 mm</td>
			<td></td>
		</tr>
		<tr>
			<td>Teflon Mold (6-cavities)</td>
			<td>Fabricated in-house</td>
			<td>Overall cavity dimensions: length 25 mm, width 8.35 mm and depth 0.8 mm; gauge dimensions: length 5 mm, width 2 mm)</td>
			<td></td>
		</tr>
		<tr>
			<td>Teflon Sheets (0.005&#34; thick)</td>
			<td>McMaster-Carr</td>
			<td>8569K61</td>
			<td></td>
		</tr>
		<tr>
			<td>Temperature Control Modules</td>
			<td>Omega</td>
			<td>C9000A and C9000</td>
			<td>&#176;C units (two modules, one for top and one for bottom)</td>
		</tr>
		<tr>
			<td>Triphenyl Phosphine</td>
			<td>TCI</td>
			<td>T0519500G</td>
			<td></td>
		</tr>
		<tr>
			<td>UV lamps</td>
			<td>Rayonet</td>
			<td>RPR2537A and RPR3000A</td>
			<td></td>
		</tr>
		<tr>
			<td>Vacuum pump</td>
			<td>Welch Duoseal</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Whatman Filter Paper (grade 2)</td>
			<td>VWR</td>
			<td>09-810F</td>
			<td>filter paper</td>
		</tr>
	</tbody>
</table>

depolymerizable olefinic polymers based on fused-ring cyclooctene monomers

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.

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&#160;with G1/PPh3 (black)18</...

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Depolymerizable Olefinic Polymers Based on Fused-Ring Cyclooctene Monomers

Here, we describe protocols for the preparation of trans-cyclobutane fused cyclooctenes (tCBCO),&#160;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.

The growing consumption of synthetic polymers and the accumulation of polymer waste have led to a pressing need for new routes to sustainable materials. ...

This protocol describes the synthesis, characterization, and the chemical recycling of a chemical recyclable polymer system developing our lamp, which we think have the potential to address the challenges associated with the sustainable use of plastics. Compared with chemically recyclable polymers developed so far, the advantage of our system is that it enables the chemical recycling of polymers with hydrocarbon backbone, which has excellent hydrolytic stability. Demonstrating the procedure will be Devavrat Sathe and Hanlin Chen, graduate students from my laboratory.To begin, add maleic anhydride, cyclooctadiene, and 150 milliliters of dry acetone to a quartz tube. Seal the quartz flask with a rubber septum and insert a 6-inch needle connected to the nitrogen on a Schlenk line and a smaller bleed needle. Stir the solution on a magnetic stir plate while bubbling with nitrogen for around 30 minutes.After that, remove the needles. Equip the photoreactor with 300-nanometer lamps, and place the flask in it, clamped to a vertical support. Make sure to cover the top of the photoreactor loosely and turn on the cooling fan and UV lamps.After irradiating overnight, concentrate the mixture on a rotavap until most of the solvent is removed. Add cotton and silver nitrate-impregnated silica gel to a circulation column, and fill the rest of the column with untreated silica gel. Add another another piece of cotton, wrap the column with aluminum foil, and connect with tubing on either end.Connect one end of the column to a metering pump for circulation, with another piece of tubing coming out of the metering pump. Put either end of the tubing into a flask with 200 millimeters diethyl ether/hexane solvent mixture and circulate for 2 hours to pack the column tight. Check any possible leaking.Next, dissolve dimethyl ester monomer, or M1, and methyl benzoate in diethyl ether/hexane solvent mixture in a quartz tube. Equip the photoreaction chamber with 254-nanometer wavelength lamps. Replace the flask with the quartz tube, place it in the photoreaction chamber, and continue circulation under irradiation for 16 hours.After turning off the photoreactor, pull the tubing up above the solution level and circulate for an additional 1 hour to dry the column. Pack another column with a silica gel layer at the bottom and silver nitrate-impregnated silica gel at the top. After emptying the circulation column, load its contents to the normal column.Collect the solution from the quartz tube and concentrate. Add this concentrated solution to the silica column. Wash the column with diethyl ether/hexane solvent mixture to collect methyl benzoate and M1, followed by washing with acetone to collect EM1 silver complex.After acetone is removed on a rotavap, add a mixture of 200 milliliters of DCM and 200 milliliters of concentrated aqueous ammonia to the residue and stir for 15 minutes. Add trans-cyclobutane fused cyclooctene monomer M2 and crosslinker XL to a 4-dram glass vial. Then, add 500 microliters of dichloromethane to this and dissolve using a vortex mixer.Add Grubbs II catalyst, or G2, to this and agitate manually to ensure dissolution. Add the solution to a polytetrafluoroethylene, or PTFE, mold with six cavities using a glass pipette. Allow the network to cure at room temperature for 24 hours and then at 6 degrees Celsius for 24 hours.Carefully remove the sample from the mold and submerge the sample in a 20-milliliter vial with around 5 milliliter of ethyl vinyl ether for 4 hous. Place the prepared sample in a cellulose thimble and then place it in a Soxhlet extraction apparatus. Affix the Soxhlet extractor onto a 500-milliliter round-bottom flask with 250 milliliter of chloroform and place it in an oil bath.Attach a condenser to the top of the Soxhlet extractor and allow the solvent to reflux for almost 14 hours. Remove the sample from the thimble, place it on a piece of paper towel placed on a clean surface, cover it, and allow the solvent to evaporate under ambient conditions for almost 6 hours. Place the sample in a 20-milliliter vial and place it under a vacuum to dry completely, weighing periodically until no weight loss is detectable.Place the polymer P1 in a 3-dram glass vial and dissolve it in 4706 microliters of deuterated chloroform. Weigh G2 in a 1-dram glass vial and add 148.6 microliters of deuterated chloroform to dissolve it. Next, add 50 microliters of the solution of G2 to the solution of P1.The total concentration of olefinic groups is therefore 25 millimolar.Split the vial's contents into three different vials and place the vials in a water bath at 30 degrees Celsius for almost 16 hours. Then, add 50 microliters of ethyl vinyl ether to this to quench G2.Follow the same procedure for the depolymerization of the polymer network PN1. Structures of trans-cyclobutane fused cyclooctene monomers for chemically recyclable polymers are shown here.Photochemical 2 2 cycloaddition of 1, 5-cyclooctadiene and maleic anhydride affords the anhydride 1, which can be readily converted to M1 and XL, M2, and M3.Reaction schemes for the synthesis of trans-cyclobutane fused cyclooctene small molecules and monomers and the synthesis of P1 by conventional and by living ring-opening metathesis polymerization are shown here. The representative image shows the GPC traces for polymer P1 prepared by living ROMP in the presence of G1 and triphenyl phosphine and conventional ROMP in the presence of G2.The depolymerization reaction scheme of trans-CBCO polymers is presented in this image. The stacked partial proton NMR spectra of polymer P1 after depolymerization and before depolymerization, monomer M1 are shown here.1H NMR spectra of network PN1 after depolymerization, crosslinker XL, and monomer M2 are presented in this figure. The representative images show the stress vs. strain curves of polymer network PN1 and polymer P3.When setting up the photocycloaddition reaction, it's important to remember to spark the reaction mixture with nitrogen.It's also important to quench the catalyst right after polymerization or depolymerization before workup. Finally, after Soxhlet extraction of the network P1, it should be dried gradually to avoid the evaporation-induced fraction. These methods can be adapted to make tCBCO polymers with many different functional groups and to prepare depolymerizable polymers with diverse material properties and to understand the substituent effect on polymerization behavior.

depolymerizable-olefinic-polymers-based-on-fused-ring-cyclooctene

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JoVE Journal

Chemistry

3.1K ビュー.  University of Akron. このプロトコルは、プラスチックの持続可能な使用に関連する課題に対処する可能性があると私たちが考えるランプを開発するケミカルリサイクル可能なポリマーシステムの合成、特性評価、およびケミカルリサイクルについて説明しています。これまでに開発されたケミカルリサイクル可能なポリマーと比較して、炭化水素骨格を持つポリマーのケミカルリサイクル?...