1
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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. [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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2
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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 2024:10.1038/s41557-024-01511-2. [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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3
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Li Z, Guo R, Zhang Z, Yong H, Guo L, Chen Z, Huang D, Zhou D. Enhancing gene transfection of poly(β-amino ester)s through modulation of amphiphilicity and chain sequence. J Control Release 2024; 368:131-139. [PMID: 38331003 DOI: 10.1016/j.jconrel.2024.02.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2023] [Revised: 01/31/2024] [Accepted: 02/05/2024] [Indexed: 02/10/2024]
Abstract
Poly(β-amino ester)s (PAEs) have emerged as a type of highly safe and efficient non-viral DNA delivery vectors. However, the influence of amphiphilicity and chain sequence on DNA transfection efficiency and safety profile remain largely unexplored. In this study, four PAEs with distinct amphiphilicity and chain sequences were synthesized. Results show that both amphiphilicity and chain sequence significantly affect the DNA binding and condensation ability of PAEs, as well as size, zeta potential and cellular uptake of PAE/DNA polyplexes. PAEs with different amphiphilicity and chain sequence exhibit cell type-dependent transfection capabilities: in human bladder transitional cell carcinoma (UM-UC-3), hydrophilic PAE (P-Philic) and amphiphilic PAE random copolymer (R-Amphilic) exhibit relatively higher gene transfection efficiency, while in human bladder epithelial immortalized cells (SV-HUC-1), hydrophobic PAE (P-Phobic), R-Amphilic, and amphiphilic PAE block copolymer (B-Amphilic) demonstrate higher transfection capability. Regardless of cell types, amphiphilic PAE block copolymer (B-Amphilic) always exhibits much lower gene transfection efficiency. In addition, in human colon cancer cells (HCT-116), P-Philic and R-Amphilic achieved superior gene transfection efficiency at high and low polymer/DNA weight ratios, respectively. Importantly, R-Amphilic can effectively deliver the gene encoding tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) to human chondrosarcoma cells SW1353 to induce their apoptosis, highlighting its potential application in cancer gene therapy. This study not only establishes a new paradigm for enhancing the gene transfection efficiency of PAEs by modulating their amphiphilicity and chain sequence but also identifies R-Amphilic as a potential candidate for the effective delivery of TRAIL gene in cancer gene therapy.
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Affiliation(s)
- Zhili Li
- School of Chemical Engineering and Technology, Xi'an Jiaotong University, Xi'an 710049, China
| | - Rui Guo
- School of Chemical Engineering and Technology, Xi'an Jiaotong University, Xi'an 710049, China
| | - Zhiyong Zhang
- Department of Colorectal and Anal Surgery, The First Affiliated Hospital of Zhengzhou University, Zhengzhou 450052, China.
| | - Haiyang Yong
- School of Chemical Engineering and Technology, Xi'an Jiaotong University, Xi'an 710049, China.
| | - Lei Guo
- Pooling Institute of Translational Medicine, Hangzhou 311100, China
| | - Zhengju Chen
- Pooling Medical Research Institutes of 100Biotech, Beijing 100006, China
| | - Dongdong Huang
- Pooling Institute of Translational Medicine, Hangzhou 311100, China
| | - Dezhong Zhou
- School of Chemical Engineering and Technology, Xi'an Jiaotong University, Xi'an 710049, China.
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4
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Clarke RW, Caputo MR, Polo Fonseca L, McGraw ML, Reilly LT, Franklin KA, Müller AJ, Chen EYX. Cyclic and Linear Tetrablock Copolymers Synthesized at Speed and Scale by Lewis Pair Polymerization of a One-Pot (Meth)acrylic Mixture and Characterized at Multiple Levels. J Am Chem Soc 2024; 146:4930-4941. [PMID: 38346332 DOI: 10.1021/jacs.3c14136] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/22/2024]
Abstract
Cyclic block copolymers (cBCP) are fundamentally intriguing materials, but their synthetic challenges that demand precision in controlling both the monomer sequence and polymer topology limit access to AB and ABC block architectures. Here, we show that cyclic ABAB tetra-BCPs (cABAB) and their linear counterpart (lABAB) can be readily obtained at a speed and scale from one-pot (meth)acrylic monomer mixtures, through coupling the Lewis pair polymerization's unique compounded-sequence control with its precision in topology control. This approach achieves fast (<15 min) and quantitative (>99%) conversion to tetra-BCPs of predesignated linear or cyclic topology at scale (40 g) in a one-pot procedure, precluding the needs for repeated chain extensions, stoichiometric addition steps, dilute conditions, and postsynthetic modifications, and/or postsynthetic ring-closure steps. The resulting lABAB and cABAB have essentially identical molecular weights (Mn = 165-168 kg mol-1) and block degrees/symmetry, allowing for direct behavioral comparisons in solution (hydrodynamic volume, intrinsic viscosity, elution time, and refractive indices), bulk (thermal transitions), and film (thermomechanical and rheometric properties and X-ray scattering patterns) states. To further the morphological characterizations, allylic side-chain functionality is exploited via the thiol-ene click chemistry to install crystalline octadecane side chains and promote phase separation between the A and B blocks, allowing visualization of microdomain formation.
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Affiliation(s)
- Ryan W Clarke
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523-1872, United States
| | - Maria Rosaria Caputo
- Polymat and Department of Polymers and Advanced Materials: Physics, Chemistry and Technology, Faculty of Chemistry, University of the Basque Country UPV/EHU, Paseo Manuel de Lardizabal 3, Donostia-San Sebastián 20018, Spain
| | - Lucas Polo Fonseca
- Polymat and Department of Polymers and Advanced Materials: Physics, Chemistry and Technology, Faculty of Chemistry, University of the Basque Country UPV/EHU, Paseo Manuel de Lardizabal 3, Donostia-San Sebastián 20018, Spain
| | - Michael L McGraw
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523-1872, United States
| | - Liam T Reilly
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523-1872, United States
| | - Kevin A Franklin
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523-1872, United States
| | - Alejandro J Müller
- Polymat and Department of Polymers and Advanced Materials: Physics, Chemistry and Technology, Faculty of Chemistry, University of the Basque Country UPV/EHU, Paseo Manuel de Lardizabal 3, Donostia-San Sebastián 20018, Spain
- IKERBASQUE, Basque Foundation for Science, Plaza Euskadi 5, Bilbao 48009, Spain
| | - Eugene Y-X Chen
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523-1872, United States
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5
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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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6
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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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7
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Miyairi M, Taniguchi T, Nishimura T, Maeda K. Facile Synthesis of Linear and Cyclic Poly(diphenylacetylene)s by Molybdenum and Tungsten Catalysis. Angew Chem Int Ed Engl 2023; 62:e202302332. [PMID: 37376740 DOI: 10.1002/anie.202302332] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Revised: 06/11/2023] [Accepted: 06/27/2023] [Indexed: 06/29/2023]
Abstract
Improved methods for the synthesis of linear and cyclic poly(diphenylacetylene)s by polymerization of the corresponding diphenylacetylenes using MoCl5 - and WCl4 -based catalytic systems have been developed. MoCl5 induces migratory insertion polymerization of diphenylacetylenes in the presence of arylation reagents such as Ph4 Sn and ArSnn Bu3 to produce cis-stereoregular linear poly(diphenylacetyelene)s with high molecular weights (number-average molar mass (Mn )=30,000-3,200,000) in good yields (up to 98 %). On the other hand, WCl4 induces ring expansion polymerization of diphenylacetylenes in the presence of Ph4 Sn or reducing reagents to produce cis-stereoregular cyclic poly(diphenylacetylene)s with high molecular weights (Mn =20,000-250,000) in moderate to good yields (up to 90 %). Both catalytic systems are applicable to the polymerization of various diphenylacetylenes having polar functional groups such as esters that are not efficiently polymerized by conventional methods using WCl6 -Ph4 Sn and TaCl5 -n Bu4 Sn systems.
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Affiliation(s)
- Mami Miyairi
- Graduate School of Natural Science and Technology, Kanazawa University Kakuma-machi, Kanazawa, 920-1192, Japan
| | - Tsuyoshi Taniguchi
- Graduate School of Natural Science and Technology, Kanazawa University Kakuma-machi, Kanazawa, 920-1192, Japan
- Nano Life Science Institute (WPI-NanoLSI), Kanazawa University Kakuma-machi, Kanazawa, 920-1192, Japan
| | - Tatsuya Nishimura
- Graduate School of Natural Science and Technology, Kanazawa University Kakuma-machi, Kanazawa, 920-1192, Japan
| | - Katsuhiro Maeda
- Graduate School of Natural Science and Technology, Kanazawa University Kakuma-machi, Kanazawa, 920-1192, Japan
- Nano Life Science Institute (WPI-NanoLSI), Kanazawa University Kakuma-machi, Kanazawa, 920-1192, Japan
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8
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El Yousfi R, Brahmi M, Dalli M, Achalhi N, Azougagh O, Tahani A, Touzani R, El Idrissi A. Recent Advances in Nanoparticle Development for Drug Delivery: A Comprehensive Review of Polycaprolactone-Based Multi-Arm Architectures. Polymers (Basel) 2023; 15:polym15081835. [PMID: 37111982 PMCID: PMC10142392 DOI: 10.3390/polym15081835] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2023] [Revised: 03/28/2023] [Accepted: 04/03/2023] [Indexed: 04/29/2023] Open
Abstract
Controlled drug delivery is a crucial area of study for improving the targeted availability of drugs; several polymer systems have been applied for the formulation of drug delivery vehicles, including linear amphiphilic block copolymers, but with some limitations manifested in their ability to form only nanoaggregates such as polymersomes or vesicles within a narrow range of hydrophobic/hydrophilic balance, which can be problematic. For this, multi-arm architecture has emerged as an efficient alternative that overcame these challenges, with many interesting advantages such as reducing critical micellar concentrations, producing smaller particles, allowing for various functional compositions, and ensuring prolonged and continuous drug release. This review focuses on examining the key variables that influence the customization of multi-arm architecture assemblies based on polycaprolactone and their impact on drug loading and delivery. Specifically, this study focuses on the investigation of the structure-property relationships in these formulations, including the thermal properties presented by this architecture. Furthermore, this work will emphasize the importance of the type of architecture, chain topology, self-assembly parameters, and comparison between multi-arm structures and linear counterparts in relation to their impact on their performance as nanocarriers. By understanding these relationships, more effective multi-arm polymers can be designed with appropriate characteristics for their intended applications.
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Affiliation(s)
- Ridouan El Yousfi
- Laboratory Applied Chemistry and Environmental (LCAE-URAC18), Faculty of Sciences of Oujda, University Mohamed Premier, Oujda 60000, Morocco
| | - Mohamed Brahmi
- Physical Chemistry of Natural Substances and Process Team, Laboratory of Applied Chemistry and Environment (LCAE-CPSUNAP), Department of Chemistry, Faculty of Sciences, University Mohamed Premier, Oujda 60000, Morocco
| | - Mohammed Dalli
- Laboratory of Microbiology, Faculty of Medicine and Pharmacy, University Mohamed Premier, Oujda 60000, Morocco
| | - Nafea Achalhi
- Laboratory Applied Chemistry and Environmental (LCAE-URAC18), Faculty of Sciences of Oujda, University Mohamed Premier, Oujda 60000, Morocco
| | - Omar Azougagh
- Laboratory of Molecular Chemistry, Materials and Environment (LMCME), Department of Chemistry, Faculty Multidisciplinary Nador, University Mohamed Premier, P. B. 300, Nador 62700, Morocco
| | - Abdesselam Tahani
- Physical Chemistry of Natural Substances and Process Team, Laboratory of Applied Chemistry and Environment (LCAE-CPSUNAP), Department of Chemistry, Faculty of Sciences, University Mohamed Premier, Oujda 60000, Morocco
| | - Rachid Touzani
- Laboratory Applied Chemistry and Environmental (LCAE-URAC18), Faculty of Sciences of Oujda, University Mohamed Premier, Oujda 60000, Morocco
| | - Abderrahmane El Idrissi
- Laboratory Applied Chemistry and Environmental (LCAE-URAC18), Faculty of Sciences of Oujda, University Mohamed Premier, Oujda 60000, Morocco
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9
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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: 3] [Impact Index Per Article: 3.0] [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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10
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Hayes G, Drain B, Lefley J, Becer CR. Hybrid Multiblock Copolymers of 2-Oxazoline and Acrylates via Cu-Catalyzed Azide–Alkyne Cycloaddition Step-Growth Mechanism. Macromolecules 2022. [DOI: 10.1021/acs.macromol.2c01865] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- Graham Hayes
- Department of Chemistry, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Ben Drain
- Department of Chemistry, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - James Lefley
- Department of Chemistry, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - C. Remzi Becer
- Department of Chemistry, University of Warwick, Coventry CV4 7AL, United Kingdom
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11
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Liu X, Li Y, Zeng L, Li X, Chen N, Bai S, He H, Wang Q, Zhang C. A Review on Mechanochemistry: Approaching Advanced Energy Materials with Greener Force. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2022; 34:e2108327. [PMID: 35015320 DOI: 10.1002/adma.202108327] [Citation(s) in RCA: 24] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2021] [Revised: 01/06/2022] [Indexed: 06/14/2023]
Abstract
Mechanochemistry with solvent-free and environmentally friendly characteristics is one of the most promising alternatives to traditional liquid-phase-based reactions, demonstrating epoch-making significance in the realization of different types of chemistry. Mechanochemistry utilizes mechanical energy to promote physical and chemical transformations to design complex molecules and nanostructured materials, encourage dispersion and recombination of multiphase components, and accelerate reaction rates and efficiencies via highly reactive surfaces. In particular, mechanochemistry deserves special attention because it is capable of endowing energy materials with unique characteristics and properties. Herein, the latest advances and progress in mechanochemistry for the preparation and modification of energy materials are reviewed. An outline of the basic knowledge, methods, and characteristics of different mechanochemical strategies is presented, distinguishing this review from most mechanochemistry reviews that only focus on ball-milling. Next, this outline is followed by a detailed and insightful discussion of mechanochemistry-involved energy conversion and storage applications. The discussion comprehensively covers aspects of energy transformations from mechanical/optical/chemical energy to electrical energy. Finally, next-generation advanced energy materials are proposed. This review is intended to bring mechanochemistry to the frontline and guide this burgeoning field of interdisciplinary research for developing advanced energy materials with greener mechanical force.
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Affiliation(s)
- Xingang Liu
- State Key Laboratory of Polymer Materials Engineering, Polymer Research Institute of Sichuan University, Chengdu, 610065, China
| | - Yijun Li
- State Key Laboratory of Polymer Materials Engineering, Polymer Research Institute of Sichuan University, Chengdu, 610065, China
| | - Li Zeng
- State Key Laboratory of Polymer Materials Engineering, Polymer Research Institute of Sichuan University, Chengdu, 610065, China
| | - Xi Li
- State Key Laboratory of Polymer Materials Engineering, Polymer Research Institute of Sichuan University, Chengdu, 610065, China
| | - Ning Chen
- State Key Laboratory of Polymer Materials Engineering, Polymer Research Institute of Sichuan University, Chengdu, 610065, China
| | - Shibing Bai
- State Key Laboratory of Polymer Materials Engineering, Polymer Research Institute of Sichuan University, Chengdu, 610065, China
| | - Hanna He
- State Key Laboratory of Polymer Materials Engineering, Polymer Research Institute of Sichuan University, Chengdu, 610065, China
| | - Qi Wang
- State Key Laboratory of Polymer Materials Engineering, Polymer Research Institute of Sichuan University, Chengdu, 610065, China
| | - Chuhong Zhang
- State Key Laboratory of Polymer Materials Engineering, Polymer Research Institute of Sichuan University, Chengdu, 610065, China
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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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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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14
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McGraw ML, Reilly LT, Clarke RW, Cavallo L, Falivene L, Chen EYX. 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: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [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 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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15
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Zhao W, Wang Q, He J, Zhang Y. Boron-Based Lewis Pairs Catalyzed Living, Regioselective and Topology-Controlled Polymerization of (E, E)-alkyl Sorbates. Macromol Rapid Commun 2022; 43:e2200088. [PMID: 35363417 DOI: 10.1002/marc.202200088] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Revised: 03/16/2022] [Indexed: 11/06/2022]
Abstract
It remains as a great challenge to realize living and controlled polymerization of renewable monomers by the boron-based Lewis pairs. Here we employ strong nucleophilic N-heterocyclic olefins (NHOs) or N-heterocyclic carbenes (NHCs) as Lewis bases (LBs), and boron-based compounds as Lewis acids (LAs) to construct LPs for polymerization of alkyl sorbates, including (E, E)-methyl sorbate (MS) and (E, E)-ethyl sorbate (ES). Systematic investigation reveal that the combinations of B(C6 F5 )3 with appropriate acidity and steric hindrance, and strong nucleophilic NHOs promote living and controlled polymerization of alkyl sorbates in 100% 1,4-addition manner, furnishing polymers with predicted molecular weight (Mw up to 56.6 kg/mol) and narrow molecular weight distribution (Đ as low as 1.12). Furthermore, topology analysis shows that NHC1/B(C6 F5 )3 LP produced PMS possessing cyclic structure. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Wuchao Zhao
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, Jilin, 130012, China
| | - Qianyi Wang
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, Jilin, 130012, China
| | - Jianghua He
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, Jilin, 130012, China
| | - Yuetao Zhang
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, Jilin, 130012, China
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16
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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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17
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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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18
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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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19
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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] [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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20
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Sueyoshi S, Taniguchi T, Tanaka S, Asakawa H, Nishimura T, Maeda K. Understanding the Polymerization of Diphenylacetylenes with Tantalum(V) Chloride and Cocatalysts: Production of Cyclic Poly(diphenylacetylene)s by Low-Valent Tantalum Species Generated in Situ. J Am Chem Soc 2021; 143:16136-16146. [PMID: 34499837 DOI: 10.1021/jacs.1c06811] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
A systematic investigation of the polymerization of representative diphenylacetylenes with TaCl5 and cocatalysts suggested that low-valent Ta species, which are formed by in situ reduction of TaCl5 by the cocatalysts, are involved in the polymerization and that the polymerization reaction proceeds by an insertion ring expansion mechanism via the formation of tantalacyclopentadiene intermediates, rather than the previously considered metathesis mechanism. This polymerization mechanism indicates the production of unprecedented cis-stereoregular cyclic poly(diphenylacetylene)s. Indeed, the possibilities of a cyclic structure and high cis-stereoregularity of the resulting polymers were reasonably supported by the results of their detailed atomic force microscopy (AFM) and NMR analyses, respectively.
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Affiliation(s)
- Shingyo Sueyoshi
- Graduate School of Frontier Science Initiative, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan
| | - Tsuyoshi Taniguchi
- Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan
| | - Saki Tanaka
- Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan
| | - Hitoshi Asakawa
- Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan.,Nanomaterials Research Institute (NanoMaRi), Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan.,Nano Life Science Institute (WPI-NanoLSI), Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan
| | - Tatsuya Nishimura
- Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan
| | - Katsuhiro Maeda
- Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan.,Nano Life Science Institute (WPI-NanoLSI), Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan
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21
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Affiliation(s)
- B. E. Eichinger
- Department of Chemistry, University of Washington, Seattle, Washington 98118, United States
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22
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Hakobyan K, McErlean CSP, Müllner M. RAFT without an “R-Group”: From Asymmetric Homo-telechelics to Multiblock Step-Growth and Cyclic Block Copolymers. Macromolecules 2021. [DOI: 10.1021/acs.macromol.1c01621] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Karen Hakobyan
- Key Centre for Polymers and Colloids, School of Chemistry, The University of Sydney, Sydney, NSW 2006, Australia
- The University of Sydney Nano Institute (Sydney Nano), Sydney, NSW 2006, Australia
| | | | - Markus Müllner
- Key Centre for Polymers and Colloids, School of Chemistry, The University of Sydney, Sydney, NSW 2006, Australia
- The University of Sydney Nano Institute (Sydney Nano), Sydney, NSW 2006, Australia
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23
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Wang TW, Huang PR, Chow JL, Kaminsky W, Golder MR. A Cyclic Ruthenium Benzylidene Initiator Platform Enhances Reactivity for Ring-Expansion Metathesis Polymerization. J Am Chem Soc 2021; 143:7314-7319. [PMID: 33960766 DOI: 10.1021/jacs.1c03491] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Ring-expansion metathesis polymerization (REMP) has shown potential as an efficient strategy to access cyclic macromolecules. Current approaches that utilize cyclic olefin feedstocks suffer from poor functional group tolerance, low initiator stability, and slow reaction kinetics. Improvements to current initiators will address these issues in order to develop more versatile and user-friendly technologies. Herein, we report a reinvigorated tethered ruthenium-benzylidene initiator, CB6, that utilizes design features from ubiquitous Grubbs-type initiators that are regularly applied in linear polymerizations. We report the controlled synthesis of functionalized cyclic poly(norbornene)s and demonstrate that judicious ligand modifications not only greatly improve kinetics but also lead to enhanced initiator stability. Overall, CB6 is an adaptable platform for the study and application of cyclic macromolecules via REMP.
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