1
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Zhou L, Reilly LT, Shi C, Quinn EC, Chen EYX. Proton-triggered topological transformation in superbase-mediated selective polymerization enables access to ultrahigh-molar-mass cyclic polymers. Nat Chem 2024; 16:1357-1365. [PMID: 38649467 DOI: 10.1038/s41557-024-01511-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2023] [Accepted: 03/18/2024] [Indexed: 04/25/2024]
Abstract
The selective synthesis of ultrahigh-molar-mass (UHMM, >2 million Da) cyclic polymers is challenging as an exceptional degree of spatiotemporal control is required to overcome the possible undesired reactions that can compete with the desired intramolecular cyclization. Here we present a counterintuitive synthetic methodology for cyclic polymers, represented here by polythioesters, which proceeds via superbase-mediated ring-opening polymerization of gem-dimethylated thiopropiolactone, followed by macromolecular cyclization triggered by protic quenching. This proton-triggered linear-to-cyclic topological transformation enables selective, linear polymer-like access to desired cyclic polythioesters, including those with UHMM surpassing 2 MDa. In addition, this method eliminates the need for stringent conditions such as high dilution to prevent or suppress linear polymer contaminants and presents the opposite scenario in which protic-free conditions are required to prevent cyclic polymer formation, which is capitalized to produce cyclic polymers on demand. Furthermore, such UHMM cyclic polythioester exhibits not only much enhanced thermostability and mechanical toughness, but it can also be quantitatively recycled back to monomer under mild conditions due to its gem-disubstitution.
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Affiliation(s)
- Li Zhou
- Department of Chemistry, Colorado State University, Fort Collins, CO, USA
| | - Liam T Reilly
- Department of Chemistry, Colorado State University, Fort Collins, CO, USA
| | - Changxia Shi
- Department of Chemistry, Colorado State University, Fort Collins, CO, USA
| | - Ethan C Quinn
- Department of Chemistry, Colorado State University, Fort Collins, CO, USA
| | - Eugene Y-X Chen
- Department of Chemistry, Colorado State University, Fort Collins, CO, USA.
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2
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Jakhar VK, Shen YH, Yadav R, Nadif SS, Ghiviriga I, Abboud KA, Lester DW, Veige AS. Tethered Alkylidenes for REMP from Carbon Disulfide Cleavage. Inorg Chem 2024; 63:12207-12217. [PMID: 38888279 DOI: 10.1021/acs.inorgchem.4c01522] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/20/2024]
Abstract
Reactions between tungsten alkylidyne [tBuOCO]W≡CtBu(THF)2 1 and sulfur containing small molecules are reported. Complex 1 reacts with CS2 to produce intermediate η2 bound CS2 complex [O2C(tBuC═)W(η2-(S,C)-CS2)(THF)] 8. Heating complex 8 provides a mixture of a monomeric tungsten sulfido complex 9 and a dimeric complex 10 in a 4:1 ratio, respectively. Heating the mixture does not perturb the ratio. Addition of excess THF in a solution of 9 and 10 (4:1) converts 10 to 9 (>96%) with concomitant loss of (CS)x. Both 9 and 10 can be selectively crystallized from the mixture. An alternative synthesis of exclusively monomeric 9 involves the reaction between 1 and PhNCS. Demonstrating ring expansion metathesis polymerization (REMP), tethered tungsten alkylidene 8 polymerizes norbornene to produce cis-selective syndiotactic cyclic polynorbornene (c-poly(NBE)).
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Affiliation(s)
- Vineet K Jakhar
- Department of Chemistry, Center for Catalysis, University of Florida, P.O. Box 117200, Gainesville, Florida 32611, United States
| | - Yu-Hsuan Shen
- Department of Chemistry, Center for Catalysis, University of Florida, P.O. Box 117200, Gainesville, Florida 32611, United States
| | - Rinku Yadav
- Department of Chemistry, Center for Catalysis, University of Florida, P.O. Box 117200, Gainesville, Florida 32611, United States
| | - Soufiane S Nadif
- Department of Chemistry, Center for Catalysis, University of Florida, P.O. Box 117200, Gainesville, Florida 32611, United States
| | - Ion Ghiviriga
- Department of Chemistry, Center for Catalysis, University of Florida, P.O. Box 117200, Gainesville, Florida 32611, United States
| | - Khalil A Abboud
- Department of Chemistry, Center for Catalysis, University of Florida, P.O. Box 117200, Gainesville, Florida 32611, United States
| | - Daniel W Lester
- Polymer Characterization Research Technology Platform, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Adam S Veige
- Department of Chemistry, Center for Catalysis, University of Florida, P.O. Box 117200, Gainesville, Florida 32611, United States
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3
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Kilgallon LJ, McFadden TP, Sigman MS, Johnson JA. Tricyclononenes and tricyclononadienes as efficient monomers for controlled ROMP: understanding structure-propagation rate relationships and enabling facile post-polymerization modification. Chem Sci 2024; 15:8334-8345. [PMID: 38846402 PMCID: PMC11151844 DOI: 10.1039/d4sc01986e] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2024] [Accepted: 05/01/2024] [Indexed: 06/09/2024] Open
Abstract
Grubbs 3rd-generation (G3) pre-catalyst-initiated ring-opening metathesis polymerization (ROMP) remains an indispensable tool in the polymer chemist's toolbox. Tricyclononenes (TCN) and tricyclononadienes (TCND) represent under-explored classes of monomers for ROMP that have the potential to both advance fundamental knowledge (e.g., structure-polymerization kinetics relationships) and serve as practical tools for the polymer chemist (e.g., post-polymerization functionalization). In this work, a library of TCN and TCND imides, monoesters, and diesters, along with their exo-norbornene counterparts, were synthesized to compare their behaviors in G3-initiated ROMP. Real-time 1H NMR was used to study their polymerization kinetics; propagation rates (k p) were extracted for each monomer. To understand the relationships between monomer structure and ROMP propagation rates, density functional theory methods were used to calculate a variety of electronic and steric parameters for each monomer. While electronic parameters (e.g., HOMO energy levels) correlated positively with the measured k p values, steric parameters generally gave improved correlations, which indicates that monomer size and shape are better predictors for k p than electronic parameters for this data set. Furthermore, the TCND diester-which contains an electron-deficient cyclobutene that is resistant to ROMP-and its polymer p(TCND) are shown to be highly reactive toward DBU-catalyzed conjugate addition reactions with thiols, providing a protecting- and activating-group free strategy for post-polymerization modification.
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Affiliation(s)
- Landon J Kilgallon
- Department of Chemistry, Massachusetts Institute of Technology Cambridge MA 02139 USA
| | - Timothy P McFadden
- Department of Chemistry, University of Utah Salt Lake City Utah 84112 USA
| | - Matthew S Sigman
- Department of Chemistry, University of Utah Salt Lake City Utah 84112 USA
| | - Jeremiah A Johnson
- Department of Chemistry, Massachusetts Institute of Technology Cambridge MA 02139 USA
- Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology 500 Main Street Cambridge MA 02139 USA
- Broad Institute of MIT and Harvard Cambridge MA 02142 USA
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4
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Probst P, Groos J, Wang D, Beck A, Gugeler K, Kästner J, Frey W, Buchmeiser MR. Stereoselective Ring Expansion Metathesis Polymerization with Cationic Molybdenum Alkylidyne N-Heterocyclic Carbene Complexes. J Am Chem Soc 2024; 146:8435-8446. [PMID: 38482664 DOI: 10.1021/jacs.3c14457] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/28/2024]
Abstract
Molybdenum alkylidyne N-heterocyclic carbene (NHC) complexes of the type [Mo(C-p-C6H4Y)(OC(R)(CF3)2)2 (L)(NHC)][B(ArF)4] (Y = OMe, NO2; R = CH3, CF3; L = none, pivalonitrile, tetrahydrofuran; NHC = 1,3-dimesitylimidazol-2-ylidene (IMes), 1,3-dimesityl-3,4-dihydroimidazol-2-ylidene (IMesH2), 1,3-dimesityl-3,4-dichloroimidazol-2-ylidene (IMesCl2), 1,3-diisopropylimidazol-2-ylidene (IiPr); B(ArF)4- = tetrakis(3,5-bis(trifluoromethyl)phen-1-yl)borate) were used in the ring expansion metathesis polymerization (REMP) of cyclic olefins. With cis-cyclooctene (cCOE) cyclic, low molecular weight oligomers were obtained at low monomer concentrations and the cyclic nature of the polymer was confirmed by MALDI-TOF measurements. High-molecular weight cyclic poly(cCOE) became available at high monomer concentrations. Also, post-REMP allowed for converting low-molecular-weight cyclic poly(cCOE) into high-molecular-weight cyclic poly(cCOE). Tailored catalysts together with suitable additives offered access to the stereoselective REMP of functional norbornenes providing functional cis-isotactic (cis-it), cis-syndiotactic (cis-st) and trans-it poly(norbornene)s with up to 99% stereoselectivity. Mechanistic details supported by density functional theory (DFT) calculations are outlined.
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Affiliation(s)
- Patrick Probst
- Institute of Polymer Chemistry, Pfaffenwaldring 55, D-70569 Stuttgart, Germany
| | - Jonas Groos
- Institute of Polymer Chemistry, Pfaffenwaldring 55, D-70569 Stuttgart, Germany
| | - Dongren Wang
- Institute of Polymer Chemistry, Pfaffenwaldring 55, D-70569 Stuttgart, Germany
| | - Alexander Beck
- Institute for Theoretical Chemistry, Pfaffenwaldring 55, D-70569 Stuttgart, Germany
| | - Katrin Gugeler
- Institute for Theoretical Chemistry, Pfaffenwaldring 55, D-70569 Stuttgart, Germany
| | - Johannes Kästner
- Institute for Theoretical Chemistry, Pfaffenwaldring 55, D-70569 Stuttgart, Germany
| | - Wolfgang Frey
- Institute of Organic Chemistry, Pfaffenwaldring 55, D-70569 Stuttgart, Germany
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5
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Ma C, Wang H, Sun R, Liao X, Han H, Xie M. Polyacetylene-Based Asymmetric Bicyclic Polymer by Blocking-Cyclization Technique. Macromol Rapid Commun 2024; 45:e2300628. [PMID: 38227809 DOI: 10.1002/marc.202300628] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Revised: 12/31/2023] [Indexed: 01/18/2024]
Abstract
A rare asymmetric bicyclic polymer containing different length of conjugated polyacetylene segments is synthesized by metathesis cyclopolymerization-mediated blocking-cyclization technique. The size of each single ring differs from each other, and the unique cyclic polymer topology is controlled by adjusting the feed ratio of monofunctional monomer to catalyst. The topological difference between linear and bicyclic polymers is confirmed by several techniques, and the visualized morphology of asymmetric bicyclic polymer is directly observed without tedious post-modification process. The photoelectric and thermal properties of polymers are investigated. This work expands the pathway for the derivation of cyclic polymers, and such unique topological structure enriches the diversity of cyclic polymer classes.
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Affiliation(s)
- Cuihong Ma
- School of Chemistry and Molecular Engineering, East China Normal University, Shanghai, 200241, China
- Ministry of Education Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou, Zhejiang, 310058, China
| | - Hao Wang
- School of Chemistry and Molecular Engineering, East China Normal University, Shanghai, 200241, China
| | - Ruyi Sun
- School of Chemistry and Molecular Engineering, East China Normal University, Shanghai, 200241, China
| | - Xiaojuan Liao
- School of Chemistry and Molecular Engineering, East China Normal University, Shanghai, 200241, China
| | - Huijing Han
- School of Chemistry and Molecular Engineering, East China Normal University, Shanghai, 200241, China
| | - Meiran Xie
- School of Chemistry and Molecular Engineering, East China Normal University, Shanghai, 200241, China
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6
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Russell JB, Konar D, Keller TM, Gau MR, Carroll PJ, Telser J, Lester DW, Veige AS, Sumerlin BS, Mindiola DJ. Metallacyclobuta-(2,3)-diene: A Bidentate Ligand for Stream-line Synthesis of First Row Transition Metal Catalysts for Cyclic Polymerization of Phenylacetylene. Angew Chem Int Ed Engl 2024; 63:e202318956. [PMID: 38109203 DOI: 10.1002/anie.202318956] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2023] [Revised: 12/13/2023] [Accepted: 12/14/2023] [Indexed: 12/20/2023]
Abstract
Described here is a direct entry to two examples of 3d transition metal catalysts that are active for the cyclic polymerization of phenylacetylene, namely, [(BDI)M{κ2 -C,C-(Me3 SiC3 SiMe3 )}] (2-M) (BDI=[ArNC(CH3 )]2 CH- , Ar=2,6-i Pr2 C6 H3 ; M=Ti, V). Catalysts are prepared in one step by the treatment of [(BDI)MCl2 ] (1-M, M=Ti, V) with 1,3-dilithioallene [Li2 (Me3 SiC3 SiMe3 )]. Complexes 2-M have been spectroscopically and structurally characterized and the polymers that are catalytically formed from phenylacetylene were verified to have a cyclic topology based on a combination of size-exclusion chromatography (SEC) and intrinsic viscosity studies. Two-electron oxidation of 2-V with nitrous oxide (N2 O) cleanly yields a [VV ] alkylidene-alkynyl oxo complex [(BDI)V(=O){κ1 -C-(=C(SiMe3 )CC(SiMe3 ))}] (3), which lends support for how this scaffold in 2-M might be operating in the polymerization of the terminal alkyne. This work demonstrates how alkylidynes can be circumvented using 1,3-dianionic allene as a segue into M-C multiple bonds.
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Affiliation(s)
- John B Russell
- Department of Chemistry, University of Pennsylvania, 231 S 34th St, Philadelphia, PA 19104, USA
| | - Debabrata Konar
- Department of Chemistry, University of Florida, Gainesville, FL 32611-7200, USA) E-mail: s
| | - Taylor M Keller
- Department of Chemistry, University of Pennsylvania, 231 S 34th St, Philadelphia, PA 19104, USA
| | - Michael R Gau
- Department of Chemistry, University of Pennsylvania, 231 S 34th St, Philadelphia, PA 19104, USA
| | - Patrick J Carroll
- Department of Chemistry, University of Pennsylvania, 231 S 34th St, Philadelphia, PA 19104, USA
| | - Joshua Telser
- Department of Biological, Physical and Health Sciences, Roosevelt University, Chicago, IL 60605, USA
| | - Daniel W Lester
- Polymer Characterization Research Technology Platform, University of Warwick, Coventry, CV4 7AL, UK
| | - Adam S Veige
- Department of Chemistry, University of Florida, Gainesville, FL 32611-7200, USA) E-mail: s
| | - Brent S Sumerlin
- Department of Chemistry, University of Florida, Gainesville, FL 32611-7200, USA) E-mail: s
| | - Daniel J Mindiola
- Department of Chemistry, University of Pennsylvania, 231 S 34th St, Philadelphia, PA 19104, USA
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7
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Duan BH, Yu JX, Gao RT, Li SY, Liu N, Wu ZQ. Controlled synthesis of cyclic helical polyisocyanides and bottlebrush polymers using a cyclic alkyne-Pd(II) catalyst. Chem Commun (Camb) 2023; 59:13002-13005. [PMID: 37830293 DOI: 10.1039/d3cc04095j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2023]
Abstract
Cyclic polymers have very unique structure and properties, and thus have drawn intense research attention. However, controlled synthesis of cyclic polymers with predictable molar mass and narrow distribution is still a challenging task. In this study, we developed a novel cyclic catalyst that initiates the ring-expansion polymerisation of isocyanides, producing a series of cyclic helical polymers with predictable molecular weight and low dispersity. Interestingly, the ring-expansion polymerization of the isocyanide macromonomers gives well-defined cyclic bottlebrush polymers. The cyclic topology was demonstrated using transmission electron microscopy.
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Affiliation(s)
- Bing-Hui Duan
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun 130012, China.
| | - Jia-Xin Yu
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun 130012, China.
| | - Run-Tan Gao
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun 130012, China.
| | - Shi-Yi Li
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun 130012, China.
| | - Na Liu
- The School of Pharmaceutical Sciences, Jilin University, 1266 Fujin Road, Changchun, Jilin 130021, P. R. China.
| | - Zong-Quan Wu
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun 130012, China.
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8
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Beauchamp AM, Chakraborty J, Ghiviriga I, Abboud KA, Lester DW, Veige AS. Ring Expansion Alkyne Metathesis Polymerization. J Am Chem Soc 2023; 145:22796-22802. [PMID: 37812163 DOI: 10.1021/jacs.3c08717] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/10/2023]
Abstract
The synthesis, characterization, and preliminary activity of an unprecedented tethered alkylidyne tungsten complex for ring expansion alkyne metathesis polymerization (REAMP) are reported. The tethered alkylidyne 7 is generated rapidly by combining alkylidyne W(CtBu)(CH2tBu)(O-2,6-i-Pr2C6H3)2 (6) with 1 equiv of an yne-ol proligand (5). Characterized by NMR studies and nuclear Overhauser effect spectroscopy, complex 7 is a dimer. Each metal center contains a tungsten-carbon triple bond tethered to the metal center via an alkoxide ligand. The polymerization of the strained cycloalkyne 3,8-didodecyloxy-5,6-dihydro-11,12-didehydrodibenzo[a,e]-[8]annulene, 8, to generate cyclic polymers was demonstrated. Size exclusion chromatography (SEC) and intrinsic viscosity (η) measurements confirm the polymer's cyclic topology.
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Affiliation(s)
- Andrew M Beauchamp
- Department of Chemistry, Center for Catalysis, University of Florida, Gainesville, Florida 32611, United States
| | - Jhonti Chakraborty
- Department of Chemistry, Center for Catalysis, University of Florida, Gainesville, Florida 32611, United States
| | - Ion Ghiviriga
- Department of Chemistry, Center for NMR Spectroscopy, University of Florida, Gainesville, Florida 32611, United States
| | - Khalil A Abboud
- Department of Chemistry, Center for Catalysis, University of Florida, Gainesville, Florida 32611, United States
| | - Daniel W Lester
- Polymer Characterization Research Technology Platform, University of Warwick, Coventry CV4 7AL, U.K
| | - Adam S Veige
- Department of Chemistry, Center for Catalysis, University of Florida, Gainesville, Florida 32611, United States
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9
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Levenson AM, Morrison CM, Huang PR, Wang TW, Carter-Schwendler Z, Golder MR. Ancillary Ligand Lability Improves Control in Cyclic Ruthenium Benzylidene Initiated Ring-Expansion Metathesis Polymerizations. ACS Macro Lett 2023; 12:1286-1292. [PMID: 37695322 DOI: 10.1021/acsmacrolett.3c00520] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/12/2023]
Abstract
The synthesis of well-defined cyclic polymers is crucial to exploring applications spanning engineering, energy, and biomedicine. These materials lack chain-ends and are therefore imbued with unique bulk properties. Despite recent advancements, the general methodology for controlled cyclic polymer synthesis via ring-expansion metathesis polymerization (REMP) remains challenging. Low initiator activity leads to high molar mass polymers at short reaction times that subsequently "evolve" to smaller polymeric products. In this work, we demonstrate that in situ addition of pyridine to the tethered ruthenium-benzylidene REMP initiator CB6 increases ancillary ligand lability to synthesize controlled and low dispersity cyclic poly(norbornene) on a short time scale without relying on molar mass evolution events.
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Affiliation(s)
- Adelaide M Levenson
- Department of Chemistry, University of Washington, Seattle, Washington 98195, United States
| | - Christine M Morrison
- Department of Chemistry, University of Washington, Seattle, Washington 98195, United States
| | - Pin-Ruei Huang
- Department of Chemistry, University of Washington, Seattle, Washington 98195, United States
| | - Teng-Wei Wang
- Department of Chemistry, University of Washington, Seattle, Washington 98195, United States
| | - Zak Carter-Schwendler
- Department of Chemistry, University of Washington, Seattle, Washington 98195, United States
| | - Matthew R Golder
- Department of Chemistry, University of Washington, Seattle, Washington 98195, United States
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10
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Jakhar VK, Shen YH, Hyun SM, Esper AM, Ghiviriga I, Abboud KA, Lester DW, Veige AS. Improved Trianionic Pincer Ligand Synthesis for Cyclic Polymer Catalysts. Organometallics 2023. [DOI: 10.1021/acs.organomet.3c00060] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/31/2023]
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11
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Song Y, He J, Zhang Y, Gilsdorf RA, Chen EYX. Recyclable cyclic bio-based acrylic polymer via pairwise monomer enchainment by a trifunctional Lewis pair. Nat Chem 2023; 15:366-376. [PMID: 36443531 DOI: 10.1038/s41557-022-01097-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Accepted: 10/19/2022] [Indexed: 11/30/2022]
Abstract
The existing catalyst/initiator systems and methodologies used for the synthesis of polymers can access only a few cyclic polymers composed entirely of a single monomer type, and the synthesis of such authentic cyclic polar vinyl polymers (acrylics) devoid of any foreign motifs remains a challenge. Here we report that a tethered B-P-B trifunctional, intramolecular frustrated Lewis pair catalyst enables the synthesis of an authentic cyclic acrylic polymer, cyclic poly(γ-methyl-α-methylene-γ-butyrolactone) (c-PMMBL), from the bio-based monomer MMBL. Detailed studies have revealed an initiation and propagation mechanism through pairwise monomer enchainment enabled by the cooperative and synergistic initiator/catalyst sites of the trifunctional catalyst. We propose that macrocyclic intermediates and transition states comprising two catalyst molecules are involved in the catalyst-regulated ring expansion and eventual cyclization, forming authentic c-PMMBL rings and concurrently regenerating the catalyst. The cyclic topology of the c-PMMBL polymers imparts an ~50 °C higher onset decomposition temperature and a much narrower degradation window compared with their linear counterparts of similar molecular weight and dispersity, while maintaining high chemical recyclability.
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Affiliation(s)
- Yanjiao Song
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, Jilin, China
| | - Jianghua He
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, Jilin, China
| | - Yuetao Zhang
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, Jilin, China.
| | - Reid A Gilsdorf
- Department of Chemistry, Colorado State University, Fort Collins, CO, USA
| | - Eugene Y-X Chen
- Department of Chemistry, Colorado State University, Fort Collins, CO, USA
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12
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Ochs J, Pagnacco CA, Barroso-Bujans F. Macrocyclic polymers: Synthesis, purification, properties and applications. Prog Polym Sci 2022. [DOI: 10.1016/j.progpolymsci.2022.101606] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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13
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Chen C, Weil T. Cyclic polymers: synthesis, characteristics, and emerging applications. NANOSCALE HORIZONS 2022; 7:1121-1135. [PMID: 35938292 DOI: 10.1039/d2nh00242f] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Cyclic polymers with a ring-like topology and no chain ends are a unique class of macromolecules. In the past several decades, significant advances have been made to prepare these fascinating polymers, which allow for the exploration of their topological effects and potential applications in various fields. In this Review, we first describe representative synthetic strategies for making cyclic polymers and their derivative topological polymers with more complex structures. Second, the unique physical properties and self-assembly behavior of cyclic polymers are discussed by comparing them with their linear analogues. Special attention is paid to highlight how polymeric rings can assemble into hierarchical macromolecular architectures. Subsequently, representative applications of cyclic polymers in different fields such as drug and gene delivery and surface functionalization are presented. Last, we envision the following key challenges and opportunities for cyclic polymers that may attract future attention: large-scale synthesis, efficient purification, programmable folding and assembly, and expansion of applications.
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Affiliation(s)
- Chaojian Chen
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
- Department of Chemistry and International Institute for Nanotechnology, Northwestern University, Evanston, Illinois 60208, USA
| | - Tanja Weil
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
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14
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Self-Supported Polymeric Ruthenium Complexes as Olefin Metathesis Catalysts in Synthesis of Heterocyclic Compounds. Catalysts 2022. [DOI: 10.3390/catal12101087] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
New ruthenium olefin metathesis catalysts containing N-heterocyclic carbene (NHC) connected by a linker tether to a benzylidene ligand were studied. Such obtained self-chelated Hoveyda–Grubbs type complexes existed in the form of an organometallic polymer but could still catalyze olefin metathesis after being dissolved in an organic solvent. Although these polymeric catalysts exhibited a slightly lower activity compared to structurally related nonpolymeric catalysts, they were successfully used in a number of ring-closing metathesis reactions leading to a variety of heterocyclic compounds, including biologically and pharmacologically related analogues of cathepsin K inhibitor and sildenafil (Viagra™). In the last case, a good solubility of a polymeric catalyst in toluene allowed the separation of the product from the catalyst via simple filtration.
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15
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Yoon KY, Noh J, Gan Q, Edwards JP, Tuba R, Choi TL, Grubbs RH. Scalable and continuous access to pure cyclic polymers enabled by 'quarantined' heterogeneous catalysts. Nat Chem 2022; 14:1242-1248. [PMID: 36064971 DOI: 10.1038/s41557-022-01034-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Accepted: 07/28/2022] [Indexed: 11/09/2022]
Abstract
Cyclic polymers are topologically interesting and envisioned as a lubricant material. However, scalable synthesis of pure cyclic polymers remains elusive. The most straightforward way is to recover a used catalyst after the synthesis of cyclic polymers and reuse it. Unfortunately, this is demanding because of the catalyst's vulnerability and inseparability from polymers, which reduce the practicality of the process. Here we develop a continuous circular process, where polymerization, polymer separation and catalyst recovery happen in situ, to dispense a pure cyclic polymer after bulk ring-expansion metathesis polymerization of cyclopentene. It is enabled by introducing silica-supported ruthenium catalysts and newly designed glassware. Different depolymerization kinetics of the cyclic polymer from its linear analogue are also discussed. This process minimizes manual labour, maximizes the security of vulnerable catalysts and guarantees the purity of cyclic polymers, thereby showcasing a prototype of a scalable access to cyclic polymers with increased turnovers (≥415,000) of precious catalysts.
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Affiliation(s)
- Ki-Young Yoon
- Arnold and Mabel Beckman Laboratory of Chemical Synthesis, Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA, USA.,Ashland Specialty Ingredients, Bridgewater, NJ, USA
| | - Jinkyung Noh
- Department of Chemistry, Seoul National University, Seoul, Republic of Korea
| | - Quan Gan
- Arnold and Mabel Beckman Laboratory of Chemical Synthesis, Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA, USA
| | - Julian P Edwards
- Arnold and Mabel Beckman Laboratory of Chemical Synthesis, Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA, USA
| | - Robert Tuba
- Institute of Materials and Environmental Chemistry, Research Centre for Natural Sciences, Budapest, Hungary
| | - Tae-Lim Choi
- Department of Chemistry, Seoul National University, Seoul, Republic of Korea. .,Department of Materials, ETH Zürich, Zürich, Switzerland.
| | - Robert H Grubbs
- Arnold and Mabel Beckman Laboratory of Chemical Synthesis, Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA, USA
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16
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Xu L, Gao B, Xu X, Zhou L, Liu N, Wu Z. Controlled Synthesis of Cyclic‐Helical Polymers with Circularly Polarized Luminescence. Angew Chem Int Ed Engl 2022; 61:e202204966. [DOI: 10.1002/anie.202204966] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2022] [Indexed: 11/10/2022]
Affiliation(s)
- Lei Xu
- State Key Laboratory of Supramolecular Structure and Materials College of Chemistry Jilin University Changchun 130012 China
| | - Bao‐Rui Gao
- Department of Polymer Science and Engineering School of Chemistry and Chemical Engineering Anhui Key Laboratory of Advanced Catalytic Materials and Reaction Engineering. Hefei University of Technology Hefei 230009, Anhui Province China
| | - Xun‐Hui Xu
- Department of Polymer Science and Engineering School of Chemistry and Chemical Engineering Anhui Key Laboratory of Advanced Catalytic Materials and Reaction Engineering. Hefei University of Technology Hefei 230009, Anhui Province China
| | - Li Zhou
- Department of Polymer Science and Engineering School of Chemistry and Chemical Engineering Anhui Key Laboratory of Advanced Catalytic Materials and Reaction Engineering. Hefei University of Technology Hefei 230009, Anhui Province China
| | - Na Liu
- Department of Polymer Science and Engineering School of Chemistry and Chemical Engineering Anhui Key Laboratory of Advanced Catalytic Materials and Reaction Engineering. Hefei University of Technology Hefei 230009, Anhui Province China
| | - Zong‐Quan Wu
- State Key Laboratory of Supramolecular Structure and Materials College of Chemistry Jilin University Changchun 130012 China
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17
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Kim M, Kim H, Kim S, Hong S, Lee E. Syntheses and Applications of Indol-2-ylidene-Ligated Ruthenium-Based Olefin Metathesis Catalysts. Organometallics 2022. [DOI: 10.1021/acs.organomet.2c00153] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Minseop Kim
- Department of Chemistry, Pohang University of Science and Technology. Pohang 37673, Republic of Korea
| | - Hyunho Kim
- Department of Chemistry, Pohang University of Science and Technology. Pohang 37673, Republic of Korea
| | - Seyong Kim
- Department of Chemistry, Gwangju Institute of Science and Technology, 123 Cheomdan-gwagiro, Buk-gu, Gwangju 61005, Republic of Korea
| | - Sukwon Hong
- Department of Chemistry, Gwangju Institute of Science and Technology, 123 Cheomdan-gwagiro, Buk-gu, Gwangju 61005, Republic of Korea
| | - Eunsung Lee
- Department of Chemistry, Pohang University of Science and Technology. Pohang 37673, Republic of Korea
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18
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Mao X, Xian J, Wang R, Han X, Pan X, Wu J. Synthesis of Linear to Cyclic Polylactide via a One-Pot Step-Wise Ring-Opening Polymerization and Back-Biting Reaction of Ring Closure Using Magnesium Complexes. Inorg Chem 2022; 61:10722-10730. [PMID: 35771955 DOI: 10.1021/acs.inorgchem.2c00935] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The controllable synthesis of cyclic polylactide remains a challenging topic so far. In this work, a new strategy of one-pot step-wise ring-opening polymerization (ROP) followed by a back-biting reaction of ring closure was reported, in which one magnesium atrane-like complex {N,N-bis[3,5-di-cumyl-2-benzyloxy]-[2-(2-aminoethoxy)ethoxy]magnesium} was utilized to initiate the ROP of lactide using 4-dimethylaminopyridine as a co-catalyst; then, macrocyclic polylactides were liberated out via increasing temperature after complete depletion of the monomer in which a back-biting reaction was utilized as a ring-closure method. The living feature at the first ROP stage can be proved well by the controllable molecular weights ranging from 3.10 to 34.70 kDa and narrow molecular weight distributions of linear polylactides obtained after quenching the reaction. The final cyclic polylactides with molecular weights (vs polystyrene) ranging from 2.50 to 16.10 kDa can be achieved too after the back-biting reaction of ring closure. Although a shoulder peak at the gel permeation chromatography profile appears when the ratio of monomer:initiator is high up to 100:1 or 200:1, this system is suitable for the controllable syntheses of cyclic polylactides with desirable modest molecular weights.
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Affiliation(s)
- Xiaoyang Mao
- State Key Laboratory of Applied Organic Chemistry (Lanzhou University), Key Laboratory of Nonferrous Metal Chemistry and Resources Utilization of Gansu Province, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, People's Republic of China
| | - Ji Xian
- State Key Laboratory of Applied Organic Chemistry (Lanzhou University), Key Laboratory of Nonferrous Metal Chemistry and Resources Utilization of Gansu Province, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, People's Republic of China
| | - Rui Wang
- State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, People's Republic of China
| | - Xinning Han
- College of Chemistry and Chemical Engineering, Ningxia Normal University, Guyuan 756000, People's Republic of China
| | - Xiaobo Pan
- State Key Laboratory of Applied Organic Chemistry (Lanzhou University), Key Laboratory of Nonferrous Metal Chemistry and Resources Utilization of Gansu Province, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, People's Republic of China
| | - Jincai Wu
- State Key Laboratory of Applied Organic Chemistry (Lanzhou University), Key Laboratory of Nonferrous Metal Chemistry and Resources Utilization of Gansu Province, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, People's Republic of China
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19
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Ma C, Quan Y, Zhang J, Sun R, Zhao Q, He X, Liao X, Xie M. Efficient Synthesis and Cyclic Molecular Topology of Ultralarge-Sized Bicyclic and Tetracyclic Polymers. Macromolecules 2022. [DOI: 10.1021/acs.macromol.1c02368] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Cuihong Ma
- School of Chemistry and Molecular Engineering, East China Normal University, Shanghai 200241, China
| | - Ying Quan
- School of Chemistry and Molecular Engineering, East China Normal University, Shanghai 200241, China
| | - Jinhuan Zhang
- School of Chemistry and Molecular Engineering, East China Normal University, Shanghai 200241, China
| | - Ruyi Sun
- School of Chemistry and Molecular Engineering, East China Normal University, Shanghai 200241, China
| | - Qiuhua Zhao
- School of Chemistry and Molecular Engineering, East China Normal University, Shanghai 200241, China
| | - Xiao He
- School of Chemistry and Molecular Engineering, East China Normal University, Shanghai 200241, China
| | - Xiaojuan Liao
- School of Chemistry and Molecular Engineering, East China Normal University, Shanghai 200241, China
| | - Meiran Xie
- School of Chemistry and Molecular Engineering, East China Normal University, Shanghai 200241, China
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20
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Xu L, Gao BR, Xu XH, Zhou L, Liu N, Wu ZQ. Controlled Synthesis of Cyclic‐Helical Polymers with Circularly Polarized Luminescence. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202204966] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Lei Xu
- Jilin University Polymer Chemistry and Physis CHINA
| | - Bao-Rui Gao
- Hefei University of Technology Polymer Science and Engineering CHINA
| | - Xun-Hui Xu
- Hefei University of Technology Polymer Science and Engineering CHINA
| | - Li Zhou
- Hefei University of Technology Polymer Science and Engineering CHINA
| | - Na Liu
- Hefei University of Technology Polymer Science and Engineering CHINA
| | - Zong-Quan Wu
- Jilin University Polymer Chemistry and Physis Qianjin Street 2699 130012 Changchun CHINA
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21
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McGraw ML, Reilly LT, Clarke RW, Cavallo L, Falivene L, Chen EY. Mechanism of Spatial and Temporal Control in Precision Cyclic Vinyl Polymer Synthesis by Lewis Pair Polymerization. Angew Chem Int Ed Engl 2022; 61:e202116303. [PMID: 35132730 PMCID: PMC9304268 DOI: 10.1002/anie.202116303] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Indexed: 11/25/2022]
Abstract
In typical cyclic polymer synthesis via ring-closure, chain growth and cyclization events are competing with each other, thus affording cyclic polymers with uncontrolled molecular weight or ring size and high dispersity. Here we uncover a mechanism by which Lewis pair polymerization (LPP) operates on polar vinyl monomers that allows the control of where and when cyclization takes place, thereby achieving spatial and temporal control to afford precision cyclic vinyl polymers or block copolymers with predictable molecular weight and low dispersity (≈1.03). A combined experimental and theoretical study demonstrates that cyclization occurs only after all monomers have been consumed (when) via conjugate addition of the propagating chain end to the specific site of the initiating chain end (where), allowing the cyclic polymer formation steps to be regulated and executed with precision in space and time.
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Affiliation(s)
- Michael L. McGraw
- Department of ChemistryColorado State UniversityFort CollinsCO 80523–1872USA
| | - Liam T. Reilly
- Department of ChemistryColorado State UniversityFort CollinsCO 80523–1872USA
| | - Ryan W. Clarke
- Department of ChemistryColorado State UniversityFort CollinsCO 80523–1872USA
| | - Luigi Cavallo
- King Abdullah University of Science and Technology (KAUST)Physical Sciences and Engineering DivisionKAUST Catalysis CenterThuwal23955-6900Saudi Arabia
| | - Laura Falivene
- Università di SalernoDipartimento di Chimica e BiologiaVia Papa Paolo Giovanni II84100Fisciano (SA)Italy
| | - Eugene Y.‐X. Chen
- Department of ChemistryColorado State UniversityFort CollinsCO 80523–1872USA
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22
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Cao Z, Wu D, Li M, Yang F, Li Z, An W, Jiang S, Zheng X, Niu C, Qu D. An acid-base responsive linear-cyclic polymer rotaxane molecular shuttle with fluorescence signal output. CHINESE CHEM LETT 2022. [DOI: 10.1016/j.cclet.2021.09.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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23
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McGraw ML, Reilly LT, Clarke RW, Cavallo L, Falivene L, Chen EY. Mechanism of Spatial and Temporal Control in Precision Cyclic Vinyl Polymer Synthesis by Lewis Pair Polymerization. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202116303] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Michael L. McGraw
- Department of Chemistry Colorado State University Fort Collins CO 80523–1872 USA
| | - Liam T. Reilly
- Department of Chemistry Colorado State University Fort Collins CO 80523–1872 USA
| | - Ryan W. Clarke
- Department of Chemistry Colorado State University Fort Collins CO 80523–1872 USA
| | - Luigi Cavallo
- King Abdullah University of Science and Technology (KAUST) Physical Sciences and Engineering Division KAUST Catalysis Center Thuwal 23955-6900 Saudi Arabia
| | - Laura Falivene
- Università di Salerno Dipartimento di Chimica e Biologia Via Papa Paolo Giovanni II 84100 Fisciano (SA) Italy
| | - Eugene Y.‐X. Chen
- Department of Chemistry Colorado State University Fort Collins CO 80523–1872 USA
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24
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Golder MR, Morrison CM. Ring-Expansion Metathesis Polymerization Initiator Design for the Synthesis of Cyclic Polymers. Synlett 2022. [DOI: 10.1055/s-0041-1737802] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
AbstractCyclic polymers are of increasing interest to the synthetic and physical polymer communities due to their unique structures that lack chain ends. This topological distinction results in decreased chain entanglement, lower intrinsic viscosity, and smaller hydrodynamic radii. Many methods for the production of cyclic polymers exist, however, large-scale production of architecturally pure cyclic polymers is challenging. Ring-expansion metathesis polymerization (REMP) is an increasingly promising method to produce cyclic polymers because of the mild and scalable reaction conditions. Herein, a brief history of REMP for the synthesis of cyclic polymers with both ruthenium and non-ruthenium initiators is discussed. Even though REMP is a promising method for synthesizing cyclic polymers, state-of-the-art methods still struggle with poor molar mass control, slow polymerization rates, low conversion, and poor initiator stability. To combat these challenges, our group has developed a tethered ruthenium-benzylidene initiator, CB6, which utilizes design features from ubiquitous Grubbs-type initiators used in linear polymerizations. These structural modifications are shown to improve initiator kinetics, enhance initiator stability, and increase control over the molar mass of the resulting cyclic polymers.1 Introduction2 Ring-Expansion Metathesis Polymerization (REMP) with Ruthenium Initiators3 New Developments in Ruthenium Ring-Expansion Metathesis (REMP) Initiator Design4 Ring-Expansion Metathesis Polymerization (REMP) with Non-Ruthenium Initiators5 Conclusions
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25
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Xie M, Ma C, Quan Y, Sun R, Song W, Liao X. Synthesis of conjugated segments-based cyclic polymers for direct imaging of cyclic molecular topology. Chem Commun (Camb) 2022; 58:4340-4343. [DOI: 10.1039/d1cc07223d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Conjugated polyacetylene-based monocyclic and bicyclic polymers were synthesized by blocking-cyclization metathesis polymerization using the short ladderphanes as the intial motif and multi-cyclizing unit, and fully characterized to elucidate the cyclic...
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26
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Pérez-Ortega I, Albéniz AC. A Different Polynorbornene Backbone by Combination of Two Polymer Growth Pathways: Vinylic Addition and Ring Opening via β-C Elimination. Chem Sci 2022; 13:1823-1828. [PMID: 35282631 PMCID: PMC8826958 DOI: 10.1039/d1sc07028b] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Accepted: 01/19/2022] [Indexed: 11/25/2022] Open
Abstract
A new polynorbornene skeleton has been found that contains bicyclic norbornane units and cyclohexenyl methyl linkages. The polymers have been synthesized using a nickel catalyst in the presence of a controlled amount of ligands with low or moderate coordination ability. The backbone structure is the result of a vinylic addition polymerization, via sequential insertions of norbornene into a Ni–C bond (bicyclic units) combined with an unusual ring opening of the norbornene structure by a β-C elimination (cyclohexenyl methyl units) to give a new Ni–C(alkyl) bond that continues the polymerization. The ring opening events are favored when the rate of propagation of the vinylic addition polymerization decreases, and this can be modulated by making the coordination of norbornene to the metal center less favorable using additional ligands. A new polynorbornene skeleton that contains a mixture of bicyclic norbornane units and cyclohexenylmethyl moieties can be obtained using a nickel catalyst.![]()
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Affiliation(s)
- Ignacio Pérez-Ortega
- IU CINQUIMA/Química Inorgánica, Universidad de Valladolid 47071 Valladolid Spain
| | - Ana C Albéniz
- IU CINQUIMA/Química Inorgánica, Universidad de Valladolid 47071 Valladolid Spain
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27
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Mandal U, Ghiviriga I, Abboud KA, Lester DW, Veige AS. Double Tethered Metallacyclobutane Catalyst for Cyclic Polymer Synthesis. J Am Chem Soc 2021; 143:17276-17283. [PMID: 34618432 DOI: 10.1021/jacs.1c08806] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
This work outlines an approach to creating a catalyst for cyclic polymer synthesis using readily available materials in only one or two steps. Combining commercially available molybdenum-alkylidene 1 with two equivalents of ene-ol proligand 2 rapidly produces, in quantitative yield (1H NMR spectroscopy), the double tethered metallacyclobutane complex 3. Characterized by variable temperature NMR studies and nuclear Overhauser effect spectroscopy (NOESY) experiments, complex 3 exhibits fluxional behavior in solution. Determined by single crystal X-ray diffraction, the solid-state structure of complex 3 reveals metrical parameters indicating that the metallacyclobutane is not predicted to undergo rapid retro-cycloaddition. However, complex 3 is a precatalyst for the polymerization of norbornene to produce cyclic polynorbornene. An NMR spectrum of a test polymerization indicates that only a small fraction of the precatalyst is activated upon exposure to monomer. Quantifying the active catalyst is possible by measuring vinyl resonances that appear in the 1H NMR spectrum. The vinyl resonances are attributable to the release of one of the tethers upon norbornene addition. Confirmation of the polymer cyclic topology comes from gel permeation chromatography (GPC), dynamic light scattering (DLS), and intrinsic viscosity (η) measurements. The double tethered metallacyclobutane complex is a novel design for catalytic cyclic polymer synthesis. The synthetic approach suggests that catalyst tuning is possible by a choice of the commercial alkylidene and alteration of the ene-ol proligand.
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Affiliation(s)
- Ushnish Mandal
- Department of Chemistry, Center for Catalysis, University of Florida, P.O. Box 117200, Gainesville, Florida 32611, United States
| | - Ion Ghiviriga
- Department of Chemistry, Center for NMR Spectroscopy, University of Florida, P.O. Box 117200, Gainesville, Florida 32611, United States
| | - Khalil A Abboud
- Department of Chemistry, Center for Catalysis, University of Florida, P.O. Box 117200, Gainesville, Florida 32611, United States
| | - Daniel W Lester
- Polymer Characterization Research Technology Platform, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Adam S Veige
- Department of Chemistry, Center for Catalysis, University of Florida, P.O. Box 117200, Gainesville, Florida 32611, United States
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