Orthogonally deconstructable and depolymerizable polysilylethers <i>via</i> entropy-driven ring-opening metathesis polymerization

Johnson, Alayna; Husted, Keith E. L.; Kilgallon, Landon J; Johnson, Jeremiah A.

doi:10.1039/d2cc02718f

Cited by 29 publications

(32 citation statements)

References 26 publications

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“…For example, as early as 1954, it was known that strong acids or bases could catalyze Si–O exchange in siloxanes (Si–O–Si groups) such as polydimethylsiloxane (PDMS) (Figure a). − Later, Guan and co-workers reported alcohol-induced Si–O bond exchange in trialkoxysilane crosslinked materials (Figure b) as well as a proposed direct Si–O bond metathesis in mono-silyl ether-crosslinked materials (Figure c). , Additionally, Du Prez and co-workers proposed an associative silanol-induced siloxane exchange process to achieve similar material remodeling (Figure d) . While these studies provide strong precedent for Si–O bond exchange in crosslinked materials, we note that there are no reports on Si–O bond exchange in BSEs (Figure e) despite their use as cleavable functionalities in polymers and related systems. − ,− Moreover, BSEs could offer greater control over the rate of network reconfiguration than other Si-based systems. We posit that the Si substituents in BSE-based materialswhich are known to dramatically influence the rate of Si–O bond cleavage and of which hundreds of variants are readily synthesized from commercially available precursors ,, will provide a route to control CAN stress relaxation dynamics.…”

Section: Resultsmentioning

confidence: 99%

Remolding and Deconstruction of Industrial Thermosets via Carboxylic Acid-Catalyzed Bifunctional Silyl Ether Exchange

et al. 2023

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Convenient strategies for the deconstruction and reprocessing of thermosets could improve the circularity of these materials, but most approaches developed to date do not involve established, high-performance engineering materials. Here, we show that bifunctional silyl ether, i.e., R′O−SiR 2 −OR′′, (BSE)-based comonomers generate covalent adaptable network analogues of the industrial thermoset polydicyclopentadiene (pDCPD) through a novel BSE exchange process facilitated by the low-cost food-safe catalyst octanoic acid. Experimental studies and density functional theory calculations suggest an exchange mechanism involving silyl ester intermediates with formation rates that strongly depend on the Si−R 2 substituents. As a result, pDCPD thermosets manufactured with BSE comonomers display temperature-and time-dependent stress relaxation as a function of their substituents. Moreover, bulk remolding of pDCPD thermosets is enabled for the first time. Altogether, this work presents a new approach toward the installation of exchangeable bonds into commercial thermosets and establishes acid-catalyzed BSE exchange as a versatile addition to the toolbox of dynamic covalent chemistry.

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Section: Resultsmentioning

confidence: 99%

Remolding and Deconstruction of Industrial Thermosets via Carboxylic Acid-Catalyzed Bifunctional Silyl Ether Exchange

et al. 2023

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“…For example, Johnson reported a low yield (i.e., ~28%) for depolymerization to obtain the original 8-membered cyclic silyl ether monomer. 36 Most of the studies in this field have focused on the synthesis of macrocycles and the use of ED-ROP chemistry as a new means of synthesizing traditional step-growth polymers. Therefore, there remains a room for studying the potentials of ED-ROP based chemically recyclable polymers.…”

Section: Introductionmentioning

confidence: 99%

“…The most well-known ED-ROP is the polymerization of elemental sulfur S 8 with a T f of 159 °C. 35 More recently, macrocyclic monomers such as silyl ethers, 36 lactones, [37][38][39][40] disulfides, 41 sulfones, 42 carbonates, 43 and hemoglobin 44 have been employed to realize ED-ROP. For ED-ROP, the equilibrium favors polymerization at high monomer concentrations due to the favorable conformational entropy.…”

Section: Introductionmentioning

confidence: 99%

Dithioacetal Polymers Capable of Chemical Recycling to Macrocyclic Monomers and Formation of Vitrimers

Kariyawasam

Rolsma

Yang

2022

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Polymers capable of chemical recycling to monomers are highly desirable to produce sustainable materials with a circular economy. We here report a highly efficient ring-chain recycling of polydithioacetal (PDTA) via ring-closing depolymerization (RCD) and entropy-driven ring-opening polymerization (ED-ROP). Pristine PDTAs can be conveniently synthesized via a one-step reaction using 3,4,5-trimethoxybenzaldehyde and α,ω-alkyl dithiols with an acid catalyst. The resulting PDTAs undergo acid-catalyzed RCD with refluxing toluene to yield a mixture of macrocycles of various sizes with conversions of 75-95%. ED-ROP of these macrocyclic monomer mixtures in solution at room temperature affords virgin PDTAs, reaching high conversions of 80-95% within 2 h. Owing to the stability of dithioacetals, PDTAs are far more stable than the acetal counterparts, resisting hydrolysis under both acidic and basic conditions. With a floor temperature below 0 °C, depolymerization is not a concern in the bulk state even in the presence of residual catalysts as polymerization is favored at higher temperatures for ED-ROP. Once crosslinked, the network behaves as a vitrimer enabled by temperature-activated interchain exchange of dithioacetals in the bulk state. The vitrimer depolymerizes into macrocyclic monomers in solvent which can repolymerize to regenerate the vitrimer.

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“…The most well-known ED-ROP is the polymerization of elemental sulfur S8 with a Tf of 159 °C. 35 More recently, macrocyclic monomers such as silyl ethers, 36 lactones, [37][38][39][40] disulfides, 41 sulfones, 42 carbonates, 43 and hemoglobin 44 have been employed to realize ED-ROP. For ED-ROP, the equilibrium favors polymerization at high monomer concentrations due to the favorable conformational entropy.…”

Section: Introductionmentioning

confidence: 99%

“…Odelius reported on a highly selective depolymerization of polycarbonates with high yields and demonstrated the chemical recyclability, 43 whereas Johnson reported a low yield (i.e., ~28%) for depolymerization to obtain the original 8-membered cyclic silyl ether monomer. 36 Most of the studies in this field have focused on the synthesis of macrocycles and the use of ED-ROP chemistry as a new means of synthesizing traditional stepgrowth polymers. Therefore, there remains a room for more studies on ED-ROP based chemically recyclable polymers.…”

Section: Introductionmentioning

confidence: 99%

Dithioacetal Polymers Capable of Chemical Recycling to Macrocyclic Monomers and Formation of Vitrimers

Kariyawasam

Rolsma

Yang

2022

Preprint

View full text Add to dashboard Cite

Polymers capable of chemical recycling to monomers are highly desirable to produce sustainable materials with a circular economy. We here report a highly efficient ring-chain recycling of linear polydithioacetal (PDTA) via ring-closing depolymerization (RCD) and entropy-driven ring-opening polymerization (ED-ROP). Furthermore, once crosslinked, the network behaves as a vitrimer enabled by temperature-activated interchain exchange of dithioacetals in the bulk state. The vitrimer depolymerizes into macrocyclic monomers in solvent which can repolymerize to regenerate the vitrimer. Pristine linear PDTAs can be conveniently synthesized via a one-step reaction using 3,4,5-trimethoxybenzaldehyde and α,ω-alkyl dithiols with an acid catalyst. The resulting PDTAs undergo acid-catalyzed RCD with refluxing toluene to yield a mixture of macrocycles of various sizes with conversions of 75-95%. ED-ROP of these macrocyclic monomer mixtures in solution at room temperature affords virgin PDTAs, reaching high conversions of 80-95% within 2 h. Owing to the stability of dithioacetals, PDTAs are far more stable than the acetal counterparts, resisting hydrolysis under both acidic and basic conditions. With a floor temperature below 0 °C, depolymerization is not a concern in the bulk state even in the presence of residual catalysts as polymerization is favored at higher temperatures for ED-ROP.

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Orthogonally deconstructable and depolymerizable polysilylethers via entropy-driven ring-opening metathesis polymerization

Abstract: The synthesis of low Tg polysilylethers via entropy-driven ring-opening metathesis polymerization is reported. These polymers can be depolymerized through olefin metathesis or deconstructed with acid or fluoride.

Cited by 29 publications

References 26 publications

Remolding and Deconstruction of Industrial Thermosets via Carboxylic Acid-Catalyzed Bifunctional Silyl Ether Exchange

Remolding and Deconstruction of Industrial Thermosets via Carboxylic Acid-Catalyzed Bifunctional Silyl Ether Exchange

Dithioacetal Polymers Capable of Chemical Recycling to Macrocyclic Monomers and Formation of Vitrimers

Dithioacetal Polymers Capable of Chemical Recycling to Macrocyclic Monomers and Formation of Vitrimers

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