1
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O'Neill RT, Boulatov R. Mechanochemical Approaches to Fundamental Studies in Soft-Matter Physics. Angew Chem Int Ed Engl 2024; 63:e202402442. [PMID: 38404161 DOI: 10.1002/anie.202402442] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2024] [Revised: 02/24/2024] [Accepted: 02/25/2024] [Indexed: 02/27/2024]
Abstract
Stretching a segment of a polymer beyond its contour length makes its (primarily backbone) bonds more dissociatively labile, which enables polymer mechanochemistry. Integrating some backbone bonds into suitably designed molecular moieties yields mechanistically and kinetically diverse chemistry, which is becoming increasingly exploitable. Examples include, most prominently, attempts to improve mechanical properties of bulk polymers, as well as prospective applications in drug delivery and synthesis. This review aims to highlight an emerging effort to apply the concepts and experimental tools of mechanochemistry to fundamental physical questions in soft matter. A succinct summary of the state-of-the-knowledge of the field, with emphasis on foundational concepts and generalizable observations, is followed by analysis of 3 recent examples of mechanochemistry yielding molecular-level details of elastomer failure, macromolecular chain dynamics in elongational flows and kinetic allostery. We conclude with reasons to assume that the highlighted approaches are generalizable to a broader range of physical problems than considered to date.
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Affiliation(s)
- Robert T O'Neill
- Department of Chemistry, University of Liverpool, University of Liverpool, Department of Chemistry, Grove Street, Liverpool, L69 7ZD
| | - Roman Boulatov
- Department of Chemistry, University of Liverpool, University of Liverpool, Department of Chemistry, Grove Street, Liverpool, L69 7ZD
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2
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Zhang M, Nixon R, Schaufelberger F, Pirvu L, De Bo G, Leigh DA. Mechanical scission of a knotted polymer. Nat Chem 2024:10.1038/s41557-024-01510-3. [PMID: 38649468 DOI: 10.1038/s41557-024-01510-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2022] [Accepted: 03/18/2024] [Indexed: 04/25/2024]
Abstract
Molecular knots and entanglements form randomly and spontaneously in both biological and synthetic polymer chains. It is known that macroscopic materials, such as ropes, are substantially weakened by the presence of knots, but until now it has been unclear whether similar behaviour occurs on a molecular level. Here we show that the presence of a well-defined overhand knot in a polymer chain substantially increases the rate of scission of the polymer under tension (≥2.6× faster) in solution, because deformation of the polymer backbone induced by the tightening knot activates otherwise unreactive covalent bonds. The fragments formed upon severing of the knotted chain differ from those that arise from cleavage of a similar, but unknotted, polymer. Our solution studies provide experimental evidence that knotting can contribute to higher mechanical scission rates of polymers. It also demonstrates that entanglement design can be used to generate mechanophores that are among the most reactive described to date, providing opportunities to increase the reactivity of otherwise inert functional groups.
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Affiliation(s)
- Min Zhang
- School of Chemistry and Molecular Engineering, East China Normal University, Shanghai, China
- Department of Chemistry, University of Manchester, Manchester, UK
| | - Robert Nixon
- Department of Chemistry, University of Manchester, Manchester, UK
| | | | - Lucian Pirvu
- Department of Chemistry, University of Manchester, Manchester, UK
| | - Guillaume De Bo
- Department of Chemistry, University of Manchester, Manchester, UK.
| | - David A Leigh
- School of Chemistry and Molecular Engineering, East China Normal University, Shanghai, China.
- Department of Chemistry, University of Manchester, Manchester, UK.
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3
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Ding S, Wang W, Germann A, Wei Y, Du T, Meisner J, Zhu R, Liu Y. Bicyclo[2.2.0]hexene: A Multicyclic Mechanophore with Reactivity Diversified by External Forces. J Am Chem Soc 2024; 146:6104-6113. [PMID: 38377579 DOI: 10.1021/jacs.3c13589] [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
Polymer mechanochemistry has been established as an enabling tool in accessing chemical reactivity and reaction pathways that are distinctive from their thermal counterparts. However, eliciting diversified reaction pathways by activating different constituent chemical bonds from the same mechanophore structure remains challenging. Here, we report the design of a bicyclo[2.2.0]hexene (BCH) mechanophore to leverage its structural simplicity and relatively low molecular symmetry to demonstrate this idea of multimodal activation. Upon changing the attachment points of pendant polymer chains, three different C-C bonds in bicyclo[2.2.0]hexene are specifically activated via externally applied force by sonication. Experimental characterization confirms that in different scenarios of polymer attachment, the regioisomers of BCH undergo different activation reactions, entailing retro-[2+2] cycloreversion, 1,3-allylic migration, and retro-4π ring-opening reactions, respectively. Control experiments with small-molecule analogues reveal that the observed diversified reactivity of BCH regioisomers is possible only with mechanical force. Theoretical studies further elucidate that the differences in the positions of substitution between regioisomers have a minimal impact on the potential energy surface of the parent BCH scaffold. The mechanochemical selectivity between different C-C bonds in each constitutional isomer is a result of selective and effective coupling of force to the aligned C-C bond in each case.
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Affiliation(s)
- Shihao Ding
- Beijing National Laboratory for Molecular Sciences, Center for Soft Matter Science and Engineering, Key Laboratory of Polymer Chemistry and Physics of Ministry of Education, and College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China
| | - Wenkai Wang
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education, and College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China
| | - Anne Germann
- Institute for Physical Chemistry, Faculty of Mathematics and Natural Sciences, Heinrich Heine University Düsseldorf, Düsseldorf, 40225, Germany
| | - Yiting Wei
- Beijing National Laboratory for Molecular Sciences, Center for Soft Matter Science and Engineering, Key Laboratory of Polymer Chemistry and Physics of Ministry of Education, and College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China
| | - Tianyi Du
- Beijing National Laboratory for Molecular Sciences, Center for Soft Matter Science and Engineering, Key Laboratory of Polymer Chemistry and Physics of Ministry of Education, and College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China
| | - Jan Meisner
- Institute for Physical Chemistry, Faculty of Mathematics and Natural Sciences, Heinrich Heine University Düsseldorf, Düsseldorf, 40225, Germany
| | - Rong Zhu
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education, and College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China
| | - Yun Liu
- Beijing National Laboratory for Molecular Sciences, Center for Soft Matter Science and Engineering, Key Laboratory of Polymer Chemistry and Physics of Ministry of Education, and College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China
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4
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Mu Q, Hu J. Polymer mechanochemistry: from single molecule to bulk material. Phys Chem Chem Phys 2024; 26:679-694. [PMID: 38112120 DOI: 10.1039/d3cp04160c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2023]
Abstract
The field of polymer mechanochemistry has experienced a renaissance over the past decades, primarily propelled by the rapid development of force-sensitive molecular units (i.e., mechanophores) and principles governing the reactivity of polymer networks for mechanochemical transduction or material strengthening. In addition to fundamental guidelines for converting mechanical energy input into chemical output, there has also been increasing focus on engineering applications of polymer mechanochemistry for specific functions, mechanically adaptive material systems, and smart devices. These endeavors are made possible by multidisciplinary approaches involving the development of multifunctional mechanophores for mechanoresponsive polymer systems, mechanochemical catalysis and synthesis, three-dimensional (3D) printed mechanochromic materials, reasonable design of polymer network topology, and computational modeling. The aim of this minireview is to provide a summary of recent advancements in covalent polymer mechanochemistry. We specifically focus on productive mechanophores, mechanical remodeling of polymeric materials, and the development of theoretical concepts.
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Affiliation(s)
- Qifeng Mu
- RIKEN Center for Emergent Matter Science, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Jian Hu
- State Key Laboratory for Strength and Vibration of Mechanical Structures, Department of Engineering Mechanics, Xi'an Jiaotong University, Xi'an 710049, P. R. China.
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5
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Yokochi H, O’Neill RT, Abe T, Aoki D, Boulatov R, Otsuka H. Sacrificial Mechanical Bond is as Effective as a Sacrificial Covalent Bond in Increasing Cross-Linked Polymer Toughness. J Am Chem Soc 2023; 145:23794-23801. [PMID: 37851530 PMCID: PMC10623562 DOI: 10.1021/jacs.3c08595] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2023] [Indexed: 10/20/2023]
Abstract
Sacrificial chemical bonds have been used effectively to increase the toughness of elastomers because such bonds dissociate at forces significantly below the fracture limit of the primary load-bearing bonds, thereby dissipating local stress. This approach owes much of its success to the ability to adjust the threshold force at which the sacrificial bonds fail at the desired rate, for example, by selecting either covalent or noncovalent sacrificial bonds. Here, we report experimental and computational evidence that a mechanical bond, responsible for the structural integrity of a rotaxane or a catenane, increases the elastomer's fracture strain, stress, and energy as much as a covalent bond of comparable mechanochemical dissociation kinetics. We synthesized and studied 6 polyacrylates cross-linked by either difluorenylsuccinonitrile (DFSN), which is an established sacrificial mechanochromic moiety; a [2]rotaxane, whose stopper allows its wheel to dethread on the same subsecond time scale as DFSN dissociates when either is under tensile force of 1.5-2 nN; a structurally homologous [2]rotaxane with a much bulkier stopper that is stable at force >5.5 nN; similarly stoppered [3]rotaxanes containing DFSN in their axles; and a control polymer with aliphatic nonsacrificial cross-links. Our data suggest that mechanochemical dethreading of a rotaxane without failure of any covalent bonds may be an important, hitherto unrecognized, contributor to the toughness of some rotaxane-cross-linked polymers and that sacrificial mechanical bonds provide a mechanism to control material fracture behavior independently of the mechanochemical response of the covalent networks, due to their distinct relationships between structure and mechanochemical reactivity.
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Affiliation(s)
- Hirogi Yokochi
- Department
of Chemical Science and Engineering, Tokyo
Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550, Japan
| | - Robert T. O’Neill
- Department
of Chemistry, University of Liverpool, Liverpool L69 7ZD, U.K.
| | - Takumi Abe
- Department
of Chemical Science and Engineering, Tokyo
Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550, Japan
| | - Daisuke Aoki
- Department
of Applied Chemistry and Biotechnology, Graduate School of Engineering, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba-shi, Chiba 263-8522, Japan
| | - Roman Boulatov
- Department
of Chemistry, University of Liverpool, Liverpool L69 7ZD, U.K.
| | - Hideyuki Otsuka
- Department
of Chemical Science and Engineering, Tokyo
Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550, Japan
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6
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He X, Tian Y, O’Neill RT, Xu Y, Lin Y, Weng W, Boulatov R. Coumarin Dimer Is an Effective Photomechanochemical AND Gate for Small-Molecule Release. J Am Chem Soc 2023; 145:23214-23226. [PMID: 37821455 PMCID: PMC10603814 DOI: 10.1021/jacs.3c07883] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2023] [Indexed: 10/13/2023]
Abstract
Stimulus-responsive gating of chemical reactions is of considerable practical and conceptual interest. For example, photocleavable protective groups and gating mechanophores allow the kinetics of purely thermally activated reactions to be controlled optically or by mechanical load by inducing the release of small-molecule reactants. Such release only in response to a sequential application of both stimuli (photomechanochemical gating) has not been demonstrated despite its unique expected benefits. Here, we describe computational and experimental evidence that coumarin dimers are highly promising moieties for realizing photomechanochemical control of small-molecule release. Such dimers are transparent and photochemically inert at wavelengths >300 nm but can be made to dissociate rapidly under tensile force. The resulting coumarins are mechanochemically and thermally stable, but rapidly release their payload upon irradiation. Our DFT calculations reveal that both strain-free and mechanochemical kinetics of dimer dissociation are highly tunable over an unusually broad range of rates by simple substitution. In head-to-head dimers, the phenyl groups act as molecular levers to allow systematic and predictable variation in the force sensitivity of the dissociation barriers by choice of the pulling axis. As a proof-of-concept, we synthesized and characterized the reactivity of one such dimer for photomechanochemically controlled release of aniline and its application for controlling bulk gelation.
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Affiliation(s)
- Xiaojun He
- Department
of Chemistry, College of Chemistry and Engineering, Xiamen University, Xiamen, Fujian 361005, China
| | - Yancong Tian
- Department
of Chemistry, University of Liverpool, Crown Street, Liverpool L69 7ZD, U.K.
| | - Robert T. O’Neill
- Department
of Chemistry, University of Liverpool, Crown Street, Liverpool L69 7ZD, U.K.
| | - Yuanze Xu
- Department
of Chemistry, College of Chemistry and Engineering, Xiamen University, Xiamen, Fujian 361005, China
| | - Yangju Lin
- Department
of Chemistry, College of Chemistry and Engineering, Xiamen University, Xiamen, Fujian 361005, China
| | - Wengui Weng
- Department
of Chemistry, College of Chemistry and Engineering, Xiamen University, Xiamen, Fujian 361005, China
| | - Roman Boulatov
- Department
of Chemistry, University of Liverpool, Crown Street, Liverpool L69 7ZD, U.K.
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7
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Ditzler RAJ, King AJ, Towell SE, Ratushnyy M, Zhukhovitskiy AV. Editing of polymer backbones. Nat Rev Chem 2023; 7:600-615. [PMID: 37542179 DOI: 10.1038/s41570-023-00514-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/12/2023] [Indexed: 08/06/2023]
Abstract
Polymers are at the epicentre of modern technological progress and the associated environmental pollution. Considerations of both polymer functionality and lifecycle are crucial in these contexts, and the polymer backbone - the core of a polymer - is at the root of these considerations. Just as the meaning of a sentence can be altered by editing its words, the function and sustainability of a polymer can also be transformed via the chemical modification of its backbone. Yet, polymer modification has primarily been focused on the polymer periphery. In this Review, we focus on the transformations of the polymer backbone by defining some concepts fundamental to this topic (for example, 'polymer backbone' and 'backbone editing') and by collecting and categorizing examples of backbone editing scattered throughout a century's worth of chemical literature, and outline critical directions for further research. In so doing, we lay the foundation for the field of polymer backbone editing and hope to accelerate its development.
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Affiliation(s)
- Rachael A J Ditzler
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Andrew J King
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Sydney E Towell
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Maxim Ratushnyy
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
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8
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O'Neill RT, Boulatov R. Experimental quantitation of molecular conditions responsible for flow-induced polymer mechanochemistry. Nat Chem 2023; 15:1214-1223. [PMID: 37430105 DOI: 10.1038/s41557-023-01266-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2022] [Accepted: 06/05/2023] [Indexed: 07/12/2023]
Abstract
Fragmentation of macromolecular solutes in rapid flows is of considerable fundamental and practical importance. The sequence of molecular events preceding chain fracture is poorly understood, because such events cannot be visualized directly but must be inferred from changes in the bulk composition of the flowing solution. Here we describe how analysis of same-chain competition between fracture of a polystyrene chain and isomerization of a chromophore embedded in its backbone yields detailed characterization of the distribution of molecular geometries of mechanochemically reacting chains in sonicated solutions. In our experiments the overstretched (mechanically loaded) chain segment grew and drifted along the backbone on the same timescale as, and in competition with, the mechanochemical reactions. Consequently, only <30% of the backbone of a fragmenting chain is overstretched, with both the maximum force and the maximum reaction probabilities located away from the chain centre. We argue that quantifying intrachain competition is likely to be mechanistically informative for any flow fast enough to fracture polymer chains.
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Affiliation(s)
| | - Roman Boulatov
- Department of Chemistry, University of Liverpool, Liverpool, UK.
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9
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Fu X, Zhu B, Hu X. Force-Triggered Atropisomerization of a Parallel Diarylethene to Its Antiparallel Diastereomers. J Am Chem Soc 2023. [PMID: 37413689 PMCID: PMC10375474 DOI: 10.1021/jacs.3c03994] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/08/2023]
Abstract
This paper describes a mechanical approach to inducing the atropisomerization of a parallel diarylethene into its antiparallel diastereomers exhibiting distinct chemical reactivity. A congested parallel diarylethene mechanophore in the (Ra,Sa)-configuration with mirror symmetry is atropisomerized to its antiparallel diastereomers with C2 symmetry under ultrasound-induced force field. The resulting stereochemistry-converted material gains symmetry-allowed reactivity toward conrotatory photocyclization.
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Affiliation(s)
- Xuancheng Fu
- Department of Chemistry, Syracuse University, Syracuse, New York 13244, United States
- BioInspired Institute, Syracuse University, Syracuse, New York 13244, United States
| | - Boyu Zhu
- Department of Chemistry, Syracuse University, Syracuse, New York 13244, United States
- BioInspired Institute, Syracuse University, Syracuse, New York 13244, United States
| | - Xiaoran Hu
- Department of Chemistry, Syracuse University, Syracuse, New York 13244, United States
- BioInspired Institute, Syracuse University, Syracuse, New York 13244, United States
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10
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Wang S, Hu Y, Kouznetsova TB, Sapir L, Chen D, Herzog-Arbeitman A, Johnson JA, Rubinstein M, Craig SL. Facile mechanochemical cycloreversion of polymer cross-linkers enhances tear resistance. Science 2023; 380:1248-1252. [PMID: 37347867 DOI: 10.1126/science.adg3229] [Citation(s) in RCA: 12] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Accepted: 05/16/2023] [Indexed: 06/24/2023]
Abstract
The mechanical properties of covalent polymer networks often arise from the permanent end-linking or cross-linking of polymer strands, and molecular linkers that break more easily would likely produce materials that require less energy to tear. We report that cyclobutane-based mechanophore cross-linkers that break through force-triggered cycloreversion lead to networks that are up to nine times as tough as conventional analogs. The response is attributed to a combination of long, strong primary polymer strands and cross-linker scission forces that are approximately fivefold smaller than control cross-linkers at the same timescales. The enhanced toughness comes without the hysteresis associated with noncovalent cross-linking, and it is observed in two different acrylate elastomers, in fatigue as well as constant displacement rate tension, and in a gel as well as elastomers.
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Affiliation(s)
- Shu Wang
- NSF Center for the Chemistry of Molecularly Optimized Networks, Duke University, Durham, NC, USA
- Department of Chemistry, Duke University, Durham, NC, USA
| | - Yixin Hu
- NSF Center for the Chemistry of Molecularly Optimized Networks, Duke University, Durham, NC, USA
- Department of Chemistry, Duke University, Durham, NC, USA
| | - Tatiana B Kouznetsova
- NSF Center for the Chemistry of Molecularly Optimized Networks, Duke University, Durham, NC, USA
- Department of Chemistry, Duke University, Durham, NC, USA
| | - Liel Sapir
- NSF Center for the Chemistry of Molecularly Optimized Networks, Duke University, Durham, NC, USA
- Thomas Lord Department of Mechanical Engineering and Materials Science, Duke University, Durham, NC, USA
| | - Danyang Chen
- NSF Center for the Chemistry of Molecularly Optimized Networks, Duke University, Durham, NC, USA
- Thomas Lord Department of Mechanical Engineering and Materials Science, Duke University, Durham, NC, USA
| | - Abraham Herzog-Arbeitman
- NSF Center for the Chemistry of Molecularly Optimized Networks, Duke University, Durham, NC, USA
- Department of Chemistry, Massachusetts Institute of Technology (MIT), Boston, MA, USA
| | - Jeremiah A Johnson
- NSF Center for the Chemistry of Molecularly Optimized Networks, Duke University, Durham, NC, USA
- Department of Chemistry, Massachusetts Institute of Technology (MIT), Boston, MA, USA
| | - Michael Rubinstein
- NSF Center for the Chemistry of Molecularly Optimized Networks, Duke University, Durham, NC, USA
- Department of Chemistry, Duke University, Durham, NC, USA
- Thomas Lord Department of Mechanical Engineering and Materials Science, Duke University, Durham, NC, USA
- Departments of Biomedical Engineering and Physics, Duke University, Durham, NC, USA
- Institute for Chemical Reaction Design and Discovery, Hokkaido University, Sapporo 001-0021, Japan
| | - Stephen L Craig
- NSF Center for the Chemistry of Molecularly Optimized Networks, Duke University, Durham, NC, USA
- Department of Chemistry, Duke University, Durham, NC, USA
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11
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Metze F, Sant S, Meng Z, Klok HA, Kaur K. Swelling-Activated, Soft Mechanochemistry in Polymer Materials. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:3546-3557. [PMID: 36848262 PMCID: PMC10018775 DOI: 10.1021/acs.langmuir.2c02801] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Revised: 01/26/2023] [Indexed: 06/12/2023]
Abstract
Swelling in polymer materials is a ubiquitous phenomenon. At a molecular level, swelling is dictated by solvent-polymer interactions, and has been thoroughly studied both theoretically and experimentally. Favorable solvent-polymer interactions result in the solvation of polymer chains. For polymers in confined geometries, such as those that are tethered to surfaces, or for polymer networks, solvation can lead to swelling-induced tensions. These tensions act on polymer chains and can lead to stretching, bending, or deformation of the material both at the micro- and macroscopic scale. This Invited Feature Article sheds light on such swelling-induced mechanochemical phenomena in polymer materials across dimensions, and discusses approaches to visualize and characterize these effects.
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12
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Wang S, Panyukov S, Craig SL, Rubinstein M. Contribution of Unbroken Strands to the Fracture of Polymer Networks. Macromolecules 2023. [DOI: 10.1021/acs.macromol.2c02139] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/09/2023]
Affiliation(s)
- Shu Wang
- Department of Chemistry, Duke University, Durham, North Carolina 27708-0346, United States
| | - Sergey Panyukov
- P. N. Lebedev Physics Institute, Russian Academy of Sciences, Moscow 117924, Russia
- Department of Theoretical Physics, Moscow Institute of Physics and Technology, Dolgoprudny 141700, Russia
| | - Stephen L. Craig
- Department of Chemistry, Duke University, Durham, North Carolina 27708-0346, United States
| | - Michael Rubinstein
- Department of Chemistry, Duke University, Durham, North Carolina 27708-0346, United States
- Department of Mechanical Engineering and Materials Science, Biomedical Engineering, and Physics, Duke University, Durham, North Carolina 27708-0300, United States
- Institute for Chemical Reaction Design and Discovery (WPI-ICReDD), Hokkaido University, Sapporo 001-0021, Japan
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13
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Cardosa-Gutierrez M, De Bo G, Duwez AS, Remacle F. Bond breaking of furan-maleimide adducts via a diradical sequential mechanism under an external mechanical force. Chem Sci 2023; 14:1263-1271. [PMID: 36756317 PMCID: PMC9891376 DOI: 10.1039/d2sc05051j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2022] [Accepted: 12/27/2022] [Indexed: 01/06/2023] Open
Abstract
Substituted furan-maleimide Diels-Alder adducts are bound by dynamic covalent bonds that make them particularly attractive mechanophores. Thermally activated [4 + 2] retro-Diels-Alder (DA) reactions predominantly proceed via a concerted mechanism in the ground electronic state. We show that an asymmetric mechanical force along the anchoring bonds in both the endo and exo isomers of proximal dimethyl furan-maleimide adducts favors a sequential pathway. The switching from a concerted to a sequential mechanism occurs at external forces of ≈1 nN. The first bond rupture occurs for a projection of the pulling force on the scissile bond at ≈4.3 nN for the exo adduct and ≈3.8 nN for the endo one. The reaction is inhibited for external forces up to ≈3.4 nN for the endo adduct and 3.6 nN for the exo one after which it is activated. In the activated region, at 4 nN, the rupture rate of the first bond for the endo adduct is computed to be ≈3 orders of magnitude larger than for the exo one in qualitative agreement with recent sonication experiments [Z. Wang and S. L. Craig, Chem. Commun., 2019, 55, 12263-12266]. In the intermediate region of the path between the rupture of the first and the second bond, the lowest singlet state exhibits a diradical character for both adducts and is close in energy to a diradical triplet state. The computed values of spin-orbit coupling along the path are too small for inducing intersystem crossings. These findings open the way for the rational design of DA mechanophores for polymer science and photochemistry.
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Affiliation(s)
| | - Guillaume De Bo
- Department of Chemistry, University of ManchesterManchesterM13 9PLUK
| | - Anne-Sophie Duwez
- UR Molecular Systems, Department of Chemistry, University of Liège 4000 Liège Belgium
| | - Francoise Remacle
- UR Molecular Systems, Department of Chemistry, University of Liège 4000 Liège Belgium
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14
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Lloyd EM, Vakil JR, Yao Y, Sottos NR, Craig SL. Covalent Mechanochemistry and Contemporary Polymer Network Chemistry: A Marriage in the Making. J Am Chem Soc 2023; 145:751-768. [PMID: 36599076 DOI: 10.1021/jacs.2c09623] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Over the past 20 years, the field of polymer mechanochemistry has amassed a toolbox of mechanophores that translate mechanical energy into a variety of functional responses ranging from color change to small-molecule release. These productive chemical changes typically occur at the length scale of a few covalent bonds (Å) but require large energy inputs and strains on the micro-to-macro scale in order to achieve even low levels of mechanophore activation. The minimal activation hinders the translation of the available chemical responses into materials and device applications. The mechanophore activation challenge inspires core questions at yet another length scale of chemical control, namely: What are the molecular-scale features of a polymeric material that determine the extent of mechanophore activation? Further, how do we marry advances in the chemistry of polymer networks with the chemistry of mechanophores to create stress-responsive materials that are well suited for an intended application? In this Perspective, we speculate as to the potential match between covalent polymer mechanochemistry and recent advances in polymer network chemistry, specifically, topologically controlled networks and the hierarchical material responses enabled by multi-network architectures and mechanically interlocked polymers. Both fundamental and applied opportunities unique to the union of these two fields are discussed.
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Affiliation(s)
- Evan M Lloyd
- Department of Chemistry, Duke University, Durham, North Carolina27708, United States
| | - Jafer R Vakil
- Department of Chemistry, Duke University, Durham, North Carolina27708, United States.,NSF Center for the Chemistry of Molecularly Optimized Networks, Duke University, Durham, North Carolina27708, United States
| | - Yunxin Yao
- Department of Chemistry, Duke University, Durham, North Carolina27708, United States.,NSF Center for the Chemistry of Molecularly Optimized Networks, Duke University, Durham, North Carolina27708, United States
| | - Nancy R Sottos
- NSF Center for the Chemistry of Molecularly Optimized Networks, Duke University, Durham, North Carolina27708, United States.,Department of Materials Science and Engineering, University of Illinois, Urbana, Illinois61801, United States
| | - Stephen L Craig
- Department of Chemistry, Duke University, Durham, North Carolina27708, United States.,NSF Center for the Chemistry of Molecularly Optimized Networks, Duke University, Durham, North Carolina27708, United States
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15
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Hsu TG, Liu S, Guan X, Yoon S, Zhou J, Chen WY, Gaire S, Seylar J, Chen H, Wang Z, Rivera J, Wu L, Ziegler CJ, McKenzie R, Wang J. Mechanochemically accessing a challenging-to-synthesize depolymerizable polymer. Nat Commun 2023; 14:225. [PMID: 36641481 PMCID: PMC9840636 DOI: 10.1038/s41467-023-35925-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2022] [Accepted: 01/09/2023] [Indexed: 01/15/2023] Open
Abstract
Polymers with low ceiling temperatures (Tc) are highly desirable as they can depolymerize under mild conditions, but they typically suffer from demanding synthetic conditions and poor stability. We envision that this challenge can be addressed by developing high-Tc polymers that can be converted into low-Tc polymers on demand. Here, we demonstrate the mechanochemical generation of a low-Tc polymer, poly(2,5-dihydrofuran) (PDHF), from an unsaturated polyether that contains cyclobutane-fused THF in each repeat unit. Upon mechanically induced cycloreversion of cyclobutane, each repeat unit generates three repeat units of PDHF. The resulting PDHF completely depolymerizes into 2,5-dihydrofuran in the presence of a ruthenium catalyst. The mechanochemical generation of the otherwise difficult-to-synthesize PDHF highlights the power of polymer mechanochemistry in accessing elusive structures. The concept of mechanochemically regulating the Tc of polymers can be applied to develop next-generation sustainable plastics.
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Affiliation(s)
- Tze-Gang Hsu
- School of Polymer Science and Polymer Engineering, The University of Akron, 170 University Ave, Akron, OH, 44325, USA
| | - Shiqi Liu
- School of Polymer Science and Polymer Engineering, The University of Akron, 170 University Ave, Akron, OH, 44325, USA
| | - Xin Guan
- School of Polymer Science and Polymer Engineering, The University of Akron, 170 University Ave, Akron, OH, 44325, USA
| | - Seiyoung Yoon
- School of Polymer Science and Polymer Engineering, The University of Akron, 170 University Ave, Akron, OH, 44325, USA
| | - Junfeng Zhou
- School of Polymer Science and Polymer Engineering, The University of Akron, 170 University Ave, Akron, OH, 44325, USA
| | - Wei-Yuan Chen
- Department of Chemistry, The University of Akron, 170 University Ave, Akron, OH, 44325, USA
| | - Sanjay Gaire
- Department of Chemistry, The University of Akron, 170 University Ave, Akron, OH, 44325, USA
| | - Joshua Seylar
- School of Polymer Science and Polymer Engineering, The University of Akron, 170 University Ave, Akron, OH, 44325, USA
| | - Hanlin Chen
- School of Polymer Science and Polymer Engineering, The University of Akron, 170 University Ave, Akron, OH, 44325, USA
| | - Zeyu Wang
- School of Polymer Science and Polymer Engineering, The University of Akron, 170 University Ave, Akron, OH, 44325, USA
| | - Jared Rivera
- School of Polymer Science and Polymer Engineering, The University of Akron, 170 University Ave, Akron, OH, 44325, USA
| | - Leyao Wu
- School of Polymer Science and Polymer Engineering, The University of Akron, 170 University Ave, Akron, OH, 44325, USA
| | - Christopher J Ziegler
- Department of Chemistry, The University of Akron, 170 University Ave, Akron, OH, 44325, USA
| | - Ruel McKenzie
- School of Polymer Science and Polymer Engineering, The University of Akron, 170 University Ave, Akron, OH, 44325, USA
| | - Junpeng Wang
- School of Polymer Science and Polymer Engineering, The University of Akron, 170 University Ave, Akron, OH, 44325, USA.
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16
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Craig SL. Concluding remarks: Fundamentals, applications and future of mechanochemistry. Faraday Discuss 2023; 241:485-491. [PMID: 36472143 DOI: 10.1039/d2fd00141a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
This paper provides a summary of the Faraday Discussions meeting on "Mechanochemistry: fundamentals, applications, and future" in the context of broad themes whose exploration might contribute to a unified framework of mechanochemical phenomena.
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Affiliation(s)
- Stephen L Craig
- Department of Chemistry, Duke University, Durham, NC 27708-0346, USA.
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17
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Wang L, Zheng X, Kouznetsova TB, Yen T, Ouchi T, Brown CL, Craig SL. Mechanochemistry of Cubane. J Am Chem Soc 2022; 144:22865-22869. [DOI: 10.1021/jacs.2c10878] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Liqi Wang
- Department of Chemistry, Duke University, Durham, North Carolina 27708, United States
| | - Xujun Zheng
- Department of Chemistry, Duke University, Durham, North Carolina 27708, United States
| | | | - Tiffany Yen
- Department of Chemistry, Duke University, Durham, North Carolina 27708, United States
| | - Tetsu Ouchi
- Department of Chemistry, Duke University, Durham, North Carolina 27708, United States
| | - Cameron L. Brown
- Department of Chemistry, Duke University, Durham, North Carolina 27708, United States
| | - Stephen L. Craig
- Department of Chemistry, Duke University, Durham, North Carolina 27708, United States
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18
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Khodayeki S, Maftuhin W, Walter M. Force Dependent Barriers from Analytic Potentials within Elastic Environments. Chemphyschem 2022; 23:e202200237. [PMID: 35703590 DOI: 10.1002/cphc.202200237] [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: 04/08/2022] [Revised: 06/14/2022] [Indexed: 01/07/2023]
Abstract
Bond rupture under the action of external forces is usually induced by temperature fluctuations, where the key quantity is the force dependent barrier that needs to be overcome. Using analytic potentials we find that these barriers are fully determined by the dissociation energy and the maximal force the potential can withstand. The barrier shows a simple dependence on these two quantities that allows for a re-interpretation of the Eyring-Zhurkov-Bell length Δ x ‡ and the expressions in theories going beyond that. It is shown that solely elastic environments do not change this barrier in contrast to the predictions of constraint geometry simulate external force (COGEF) strategies. The findings are confirmed by explicit calculations of bond rupture in a polydimethylsiloxane model.
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Affiliation(s)
- Samaneh Khodayeki
- Freiburger Institut für Interaktive Materialien und Bioinspirierte Technologien, Georges-Köhler-Allee 105, 79110, Freiburg, Germany.,Physikalisches Institut, Universität Freiburg, Herrmann-Herder-Straße 3, 79104, Freiburg, Germany
| | - Wafa Maftuhin
- Freiburger Institut für Interaktive Materialien und Bioinspirierte Technologien, Georges-Köhler-Allee 105, 79110, Freiburg, Germany.,Physikalisches Institut, Universität Freiburg, Herrmann-Herder-Straße 3, 79104, Freiburg, Germany
| | - Michael Walter
- Freiburger Institut für Interaktive Materialien und Bioinspirierte Technologien, Georges-Köhler-Allee 105, 79110, Freiburg, Germany.,Physikalisches Institut, Universität Freiburg, Herrmann-Herder-Straße 3, 79104, Freiburg, Germany.,Cluster of Excellence livMatS@FIT, Freiburg, Germany.,Fraunhofer Institut für Werkstoffmechanik, Wöhlerstraße 11, 79108, Freiburg, Germany
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19
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Du M, Houck HA, Yin Q, Xu Y, Huang Y, Lan Y, Yang L, Du Prez FE, Chang G. Force-reversible chemical reaction at ambient temperature for designing toughened dynamic covalent polymer networks. Nat Commun 2022; 13:3231. [PMID: 35680925 PMCID: PMC9184613 DOI: 10.1038/s41467-022-30972-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2021] [Accepted: 05/26/2022] [Indexed: 11/23/2022] Open
Abstract
Force-reversible C-N bonds, resulting from the click chemistry reaction between triazolinedione (TAD) and indole derivatives, offer exciting opportunities for molecular-level engineering to design materials that respond to mechanical loads. Here, we displayed that TAD-indole adducts, acting as crosslink points in dry-state covalently crosslinked polymers, enable materials to display reversible stress-responsiveness in real time already at ambient temperature. Whereas the exergonic TAD-indole reaction results in the formation of bench-stable adducts, they were shown to dissociate at ambient temperature when embedded in a polymer network and subjected to a stretching force to recover the original products. Moreover, the nascent TAD moiety can spontaneously and immediately be recombined after dissociation with an indole reaction partners at ambient temperature, thus allowing for the adjustment of the polymer segment conformation and the maintenance of the network integrity by force-reversible behaviors. Overall, our strategy represents a general method to create toughened covalently crosslinked polymer materials with simultaneous enhancement of mechanical strength and ductility, which is quite challenging to achieve by conventional chemical methods. Weak force-activated covalent bonds as crosslink points can increase mechanical strength and ductility in polymers but the bonds, once broken, cannot be reformed in real time under ambient conditions leading to irreversible damage. Here, the authors demonstrate that triazolinedione (TAD)-indole adducts acting as crosslink points enable materials to display already at ambient temperature reversible stress-responsiveness in real time.
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Affiliation(s)
- Mengqi Du
- State Key Laboratory of Environment-friendly Energy Materials & School of Materials and Chemistry, Southwest University of Science and Technology, Mianyang, 621010, P. R. China
| | - Hannes A Houck
- Polymer Chemistry Research Group, Centre of Macromolecular Chemistry (CMaC), Department of Organic and Macromolecular Chemistry, Ghent University, Krijgslaan 281 S4-bis, B-9000, Ghent, Belgium
| | - Qiang Yin
- Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang, 621900, P. R. China
| | - Yewei Xu
- State Key Laboratory of Environment-friendly Energy Materials & School of Materials and Chemistry, Southwest University of Science and Technology, Mianyang, 621010, P. R. China
| | - Ying Huang
- State Key Laboratory of Environment-friendly Energy Materials & School of Materials and Chemistry, Southwest University of Science and Technology, Mianyang, 621010, P. R. China
| | - Yang Lan
- Melville Laboratory for Polymer Synthesis, Department of Chemistry, University of Cambridge, Cambridge, CB2 1EW, UK
| | - Li Yang
- State Key Laboratory of Environment-friendly Energy Materials & School of Materials and Chemistry, Southwest University of Science and Technology, Mianyang, 621010, P. R. China. .,Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, PA, 19104, USA.
| | - Filip E Du Prez
- Polymer Chemistry Research Group, Centre of Macromolecular Chemistry (CMaC), Department of Organic and Macromolecular Chemistry, Ghent University, Krijgslaan 281 S4-bis, B-9000, Ghent, Belgium.
| | - Guanjun Chang
- State Key Laboratory of Environment-friendly Energy Materials & School of Materials and Chemistry, Southwest University of Science and Technology, Mianyang, 621010, P. R. China. .,Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, PA, 19104, USA.
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20
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Cao N, Zhao Y, Chen H, Huang J, Yu M, Bao Y, Wang D, Cui S. Poly(ethylene glycol) Becomes a Supra-Polyelectrolyte by Capturing Hydronium Ions in Water. Macromolecules 2022. [DOI: 10.1021/acs.macromol.2c00014] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Nanpu Cao
- Key Laboratory of Advanced Technologies of Materials (Ministry of Education), Southwest Jiaotong University, Chengdu 610031, China
| | - Yuehua Zhao
- State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China
| | - Hongbo Chen
- State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China
| | - Jinying Huang
- School of Optoelectronic Science, Changchun College of Electronic Technology, Changchun 130114, China
| | - Miao Yu
- Key Laboratory of Advanced Technologies of Materials (Ministry of Education), Southwest Jiaotong University, Chengdu 610031, China
| | - Yu Bao
- Key Laboratory of Advanced Technologies of Materials (Ministry of Education), Southwest Jiaotong University, Chengdu 610031, China
| | - Dapeng Wang
- State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China
| | - Shuxun Cui
- Key Laboratory of Advanced Technologies of Materials (Ministry of Education), Southwest Jiaotong University, Chengdu 610031, China
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21
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Hu H, Cheng X, Ma Z, Wang Z, Ma Z. A double-spiro ring-structured mechanophore with dual-signal mechanochromism and multistate mechanochemical behavior: non-sequential ring-opening and multimodal analysis. Polym Chem 2022. [DOI: 10.1039/d2py00728b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We have developed a novel aminobenzopyranoxanthene-based mechanophore with a dual-signal response and two mechanogenerated ring-opened isomers, of which the relative distribution is modulated by external force based on the heat–force equilibrium.
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Affiliation(s)
- Huan Hu
- Beijing Advanced Innovation Center for Soft Matter Science and Engineering, State Key Laboratory of Organic-Inorganic Composites, College of Chemical Engineering, Beijing University of Chemical Technology, Beijing 100029, China
| | - Xin Cheng
- Beijing Advanced Innovation Center for Soft Matter Science and Engineering, State Key Laboratory of Organic-Inorganic Composites, College of Chemical Engineering, Beijing University of Chemical Technology, Beijing 100029, China
| | - Zhimin Ma
- College of Engineering, Peking University, Beijing 100871, China
| | - Zhijian Wang
- Key Laboratory of Aerospace Advanced Materials and Performance, Ministry of Education, School of Materials Science and Engineering, Beihang University, Beijing 100191, China
| | - Zhiyong Ma
- Beijing Advanced Innovation Center for Soft Matter Science and Engineering, State Key Laboratory of Organic-Inorganic Composites, College of Chemical Engineering, Beijing University of Chemical Technology, Beijing 100029, China
- State Key Laboratory of Molecular Engineering of Polymers, Fudan University, Shanghai 200438, China
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22
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Miller KA, Dodo OJ, Devkota GP, Kirinda VC, Bradford KGE, Sparks J, Hartley CS, Konkolewicz D. Aromatic Foldamers as Molecular Springs in Network Polymers. Chem Commun (Camb) 2022; 58:5590-5593. [DOI: 10.1039/d2cc01223e] [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
Polymer networks crosslinked with spring-like ortho-phenylene (oP) foldamers were developed. NMR analysis indicated the oP crosslinkers were well-folded. Polymer networks with oP-based crosslinkers showed enhanced energy dissipation and elasticity compared...
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23
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Truong VX, Rodrigues LL, Barner-Kowollik C. Light- and mechanic field controlled dynamic soft matter materials. Polym Chem 2022. [DOI: 10.1039/d2py00892k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A photochemical reaction system that fuses photo- and mechanochemistry into one macromolecular design for light- and mechano-reversible modification of polymer endgroups is introduced.
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Affiliation(s)
- Vinh X. Truong
- Centre for Materials Science, Queensland University of Technology, 2 George Street, Brisbane, QLD 4000, Australia
- School of Chemistry and Physics, Queensland University of Technology, 2 George Street, Brisbane, QLD 4000, Australia
| | - Leona L. Rodrigues
- Centre for Materials Science, Queensland University of Technology, 2 George Street, Brisbane, QLD 4000, Australia
- School of Chemistry and Physics, Queensland University of Technology, 2 George Street, Brisbane, QLD 4000, Australia
| | - Christopher Barner-Kowollik
- Centre for Materials Science, Queensland University of Technology, 2 George Street, Brisbane, QLD 4000, Australia
- School of Chemistry and Physics, Queensland University of Technology, 2 George Street, Brisbane, QLD 4000, Australia
- Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
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24
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Versaw BA, Zeng T, Hu X, Robb MJ. Harnessing the Power of Force: Development of Mechanophores for Molecular Release. J Am Chem Soc 2021; 143:21461-21473. [PMID: 34927426 DOI: 10.1021/jacs.1c11868] [Citation(s) in RCA: 37] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Polymers that release small molecules in response to mechanical force are promising materials for a variety of applications ranging from sensing and catalysis to targeted drug delivery. Within the rapidly growing field of polymer mechanochemistry, stress-sensitive molecules known as mechanophores are particularly attractive for enabling the release of covalently bound payloads with excellent selectivity and control. Here, we review recent progress in the development of mechanophore-based molecular release platforms and provide an optimistic, yet critical perspective on the fundamental and technological advancements that are still required for this promising research area to achieve significant impact.
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Affiliation(s)
- Brooke A Versaw
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Tian Zeng
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Xiaoran Hu
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Maxwell J Robb
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
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25
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Küng R, Göstl R, Schmidt BM. Release of Molecular Cargo from Polymer Systems by Mechanochemistry. Chemistry 2021; 28:e202103860. [PMID: 34878679 PMCID: PMC9306765 DOI: 10.1002/chem.202103860] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2021] [Indexed: 11/15/2022]
Abstract
The design and manipulation of (multi)functional materials at the nanoscale holds the promise of fuelling tomorrow's major technological advances. In the realm of macromolecular nanosystems, the incorporation of force‐responsive groups, so called mechanophores, has resulted in unprecedented access to responsive behaviours and enabled sophisticated functions of the resulting structures and advanced materials. Among the diverse force‐activated motifs, the on‐demand release or activation of compounds, such as catalysts, drugs, or monomers for self‐healing, are sought‐after since they enable triggering pristine small molecule function from macromolecular frameworks. Here, we highlight examples of molecular cargo release systems from polymer‐based architectures in solution by means of sonochemical activation by ultrasound (ultrasound‐induced mechanochemistry). Important design concepts of these advanced materials are discussed, as well as their syntheses and applications.
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Affiliation(s)
- Robin Küng
- Heinrich-Heine-Univerität Düsseldorf, Department of Chemistry, GERMANY
| | - Robert Göstl
- DWI-Leibniz-Institut für Interaktive Materialien: DWI-Leibniz-Institut fur Interaktive Materialien, Department of Chemistry, GERMANY
| | - Bernd M Schmidt
- Heinrich-Heine-Universitat Dusseldorf, Institute of Organic Chemistry and Macromolecular Chemistry, Universitätsstraße 1, 26.33.U1.R38, 40225, Düsseldorf, GERMANY
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26
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O’Neill RT, Boulatov R. The Contributions of Model Studies for Fundamental Understanding of Polymer Mechanochemistry. Synlett 2021. [DOI: 10.1055/a-1710-5656] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
AbstractThe exciting field of polymer mechanochemistry has made great empirical progress in discovering reactions in which a stretching force accelerates scission of strained bonds using single molecule force spectroscopy and ultrasonication experiments. Understanding why these reactions happen, i.e., the fundamental physical processes that govern coupling of macroscopic motion to chemical reactions, as well as discovering other patterns of mechanochemical reactivity require complementary techniques, which permit a much more detailed characterization of reaction mechanisms and the distribution of force in reacting molecules than are achievable in SMFS or ultrasonication. A molecular force probe allows the specific pattern of molecular strain that is responsible for localized reactions in stretched polymers to be reproduced accurately in non-polymeric substrates using molecular design rather than atomistically intractable collective motions of millions of atoms comprising macroscopic motion. In this review, we highlight the necessary features of a useful molecular force probe and describe their realization in stiff stilbene macrocycles. We describe how studying these macrocycles using classical tools of physical organic chemistry has allowed detailed characterizations of mechanochemical reactivity, explain some of the most unexpected insights enabled by these probes, and speculate how they may guide the next stage of mechanochemistry.
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Affiliation(s)
| | - Roman Boulatov
- Department of Chemistry, University of Liverpool
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University
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27
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Wang T, Wang H, Shen L, Zhang N. Force-induced strengthening of a mechanochromic polymer based on a naphthalene-fused cyclobutane mechanophore. Chem Commun (Camb) 2021; 57:12675-12678. [PMID: 34779466 DOI: 10.1039/d1cc05305a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We discovered a force-induced strengthening of a mechanochromic polymer based on a naphthalene-fused cyclobutane mechanophore (NCD). Our results revealed that mechanically induced retro-cycloaddition of the NCD and subsequent crosslinking reactions between CC bonds were responsible for this peculiar strenghthening, and demonstrated the good possibility that the NCD can be applied in smart materials fields.
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Affiliation(s)
- Taisheng Wang
- School of Materials Science and Engineering, Nanjing Institute of Technology, Nanjing, 211167, P. R. China. .,Jiangsu Key Laboratory of Advanced Structural Materials and Application Technology, Nanjing, 211167, P. R. China
| | - Haoxiang Wang
- School of Materials Science and Engineering, Nanjing Institute of Technology, Nanjing, 211167, P. R. China.
| | - Lei Shen
- School of Materials Science and Engineering, Nanjing Institute of Technology, Nanjing, 211167, P. R. China.
| | - Na Zhang
- School of Materials Science and Engineering, Nanjing Institute of Technology, Nanjing, 211167, P. R. China. .,Jiangsu Key Laboratory of Advanced Structural Materials and Application Technology, Nanjing, 211167, P. R. China
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28
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Abstract
AbstractThis Account covers the recent progress made on heterocyclic mechanophores in the field of polymer mechanochemistry. In particular, the types of such mechanophores as well as the mechanisms and applications of their force-induced structural transformations are discussed and related perspectives and future challenges proposed.1 Introduction2 Types of Mechanophores3 Methods to Incorporate Heterocycle Mechanophores into Polymer Systems4 Mechanochemical Reactions of Heterocyclic Mechanophores4.1 Three-Membered-Ring Mechanophores4.2 Four-Membered-Ring Mechanophores4.3 Six-Membered-Ring Mechanophores4.4 Bicyclic Mechanophores5 Applications5.1 Cross-Linking of Polymer5.2 Degradable Polymer5.3 Mechanochromic Polymer6 Concluding Remarks and Outlook
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29
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Qi Q, Sekhon G, Chandradat R, Ofodum NM, Shen T, Scrimgeour J, Joy M, Wriedt M, Jayathirtha M, Darie CC, Shipp DA, Liu X, Lu X. Force-Induced Near-Infrared Chromism of Mechanophore-Linked Polymers. J Am Chem Soc 2021; 143:17337-17343. [PMID: 34586805 DOI: 10.1021/jacs.1c05923] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A near-infrared (NIR) mechanophore was developed and incorporated into a poly(methyl acrylate) chain to showcase the first force-induced NIR chromism in polymeric materials. This mechanophore, based on benzo[1,3]oxazine (OX) fused with a heptamethine cyanine moiety, exhibited NIR mechanochromism in solution, thin-film, and bulk states. The mechanochemical activity was validated using UV-vis-NIR absorption/fluorescence spectroscopies, gel permeation chromatography (GPC), NMR, and DFT simulations. Our work demonstrates that NIR mechanochromic polymers have considerable potential in mechanical force sensing, damage detection, bioimaging, and biomechanics.
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Affiliation(s)
| | | | | | | | - Tianruo Shen
- Fluorescence Research Group, Singapore University of Technology and Design, 8 Somapah Road, 487372 Singapore
| | | | | | | | | | | | | | - Xiaogang Liu
- Fluorescence Research Group, Singapore University of Technology and Design, 8 Somapah Road, 487372 Singapore
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30
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Barber RW, Robb MJ. A modular approach to mechanically gated photoswitching with color-tunable molecular force probes. Chem Sci 2021; 12:11703-11709. [PMID: 34659705 PMCID: PMC8442728 DOI: 10.1039/d1sc02890a] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2021] [Accepted: 07/21/2021] [Indexed: 12/21/2022] Open
Abstract
Molecular force probes conveniently report on mechanical stress and/or strain in polymers through straightforward visual cues. Unlike conventional mechanochromic mechanophores, the mechanically gated photoswitching strategy decouples mechanochemical activation from the ultimate chromogenic response, enabling the mechanical history of a material to be recorded and read on-demand using light. Here we report a completely redesigned, highly modular mechanophore platform for mechanically gated photoswitching that offers a robust, accessible synthesis and late stage diversification through Pd-catalyzed cross-coupling reactions to precisely tune the photophysical properties of the masked diarylethene (DAE) photoswitch. Using solution-phase ultrasonication, the reactivity of a small library of functionally diverse mechanophores is demonstrated to be exceptionally selective, producing a chromogenic response under UV irradiation only after mechanochemical activation, revealing colored DAE isomers with absorption spectra that span the visible region of the electromagnetic spectrum. Notably, mechanically gated photoswitching is successfully translated to solid polymeric materials for the first time, demonstrating the potential of the masked diarylethene mechanophore for a variety of applications in force-responsive polymeric materials.
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Affiliation(s)
- Ross W Barber
- Division of Chemistry and Chemical Engineering, California Institute of Technology Pasadena California 91125 USA
| | - Maxwell J Robb
- Division of Chemistry and Chemical Engineering, California Institute of Technology Pasadena California 91125 USA
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31
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Yu Y, Wang C, Wang L, Sun CL, Boulatov R, Widenhoefer RA, Craig SL. Force-modulated reductive elimination from platinum(ii) diaryl complexes. Chem Sci 2021; 12:11130-11137. [PMID: 34522310 PMCID: PMC8386663 DOI: 10.1039/d1sc03182a] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2021] [Accepted: 07/19/2021] [Indexed: 11/21/2022] Open
Abstract
Coupled mechanical forces are known to drive a range of covalent chemical reactions, but the effect of mechanical force applied to a spectator ligand on transition metal reactivity is relatively unexplored. Here we quantify the rate of C(sp2)-C(sp2) reductive elimination from platinum(ii) diaryl complexes containing macrocyclic bis(phosphine) ligands as a function of mechanical force applied to these ligands. DFT computations reveal complex dependence of mechanochemical kinetics on the structure of the force-transducing ligand. We validated experimentally the computational finding for the most sensitive of the ligand designs, based on MeOBiphep, by coupling it to a macrocyclic force probe ligand. Consistent with the computations, compressive forces decreased the rate of reductive elimination whereas extension forces increased the rate relative to the strain-free MeOBiphep complex with a 3.4-fold change in rate over a ∼290 pN range of restoring forces. The calculated natural bite angle of the free macrocyclic ligand changes with force, but 31P NMR analysis and calculations strongly suggest no significant force-induced perturbation of ground state geometry within the first coordination sphere of the (P-P)PtAr2 complexes. Rather, the force/rate behavior observed across this range of forces is attributed to the coupling of force to the elongation of the O⋯O distance in the transition state for reductive elimination. The results suggest opportunities to experimentally map geometry changes associated with reactions in transition metal complexes and potential strategies for force-modulated catalysis.
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Affiliation(s)
- Yichen Yu
- Department of Chemistry, Duke University Durham North Carolina 27708 USA
| | - Chenxu Wang
- Department of Chemistry, University of Liverpool Crown Street Liverpool L69 7ZD UK
| | - Liqi Wang
- Department of Chemistry, Duke University Durham North Carolina 27708 USA
| | - Cai-Li Sun
- Department of Chemistry, University of Liverpool Crown Street Liverpool L69 7ZD UK
| | - Roman Boulatov
- Department of Chemistry, University of Liverpool Crown Street Liverpool L69 7ZD UK
| | - Ross A Widenhoefer
- Department of Chemistry, Duke University Durham North Carolina 27708 USA
| | - Stephen L Craig
- Department of Chemistry, Duke University Durham North Carolina 27708 USA
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32
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Horst M, Yang J, Meisner J, Kouznetsova TB, Martínez TJ, Craig SL, Xia Y. Understanding the Mechanochemistry of Ladder-Type Cyclobutane Mechanophores by Single Molecule Force Spectroscopy. J Am Chem Soc 2021; 143:12328-12334. [PMID: 34310875 DOI: 10.1021/jacs.1c05857] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
We have recently reported a series of ladder-type cyclobutane mechanophores, polymers of which can transform from nonconjugated structures to conjugated structures and change many properties at once. These multicyclic mechanophores, namely, exo-ladderane/ene, endo-benzoladderene, and exo-bicyclohexene-peri-naphthalene, have different ring structures fused to the first cyclobutane, significantly different free energy changes for ring-opening, and different stereochemistry. To better understand their mechanochemistry, we used single molecule force spectroscopy (SMFS) to characterize their force-extension behavior and measure the threshold forces. The threshold forces correlate with the activation energy of the first bond, but not with the strain of the fused rings distal to the polymer main chain, suggesting that the activation of these ladder-type mechanophores occurs with similar early transition states, which is supported by force-modified potential energy surface calculations. We further determined the stereochemistry of the mechanically generated dienes and observed significant and variable contour length elongation for these mechanophores both experimentally and computationally. The fundamental understanding of ladder-type mechanophores will facilitate future design of multicyclic mechanophores with amplified force-response and their applications as mechanically responsive materials.
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Affiliation(s)
- Matías Horst
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Jinghui Yang
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Jan Meisner
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Tatiana B Kouznetsova
- Department of Chemistry, Duke University, Durham, North Carolina 27708, United States
| | - Todd J Martínez
- Department of Chemistry, Stanford University, Stanford, California 94305, United States.,SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
| | - Stephen L Craig
- Department of Chemistry, Duke University, Durham, North Carolina 27708, United States
| | - Yan Xia
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
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33
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Hu X, Zeng T, Husic CC, Robb MJ. Mechanically Triggered Release of Functionally Diverse Molecular Payloads from Masked 2-Furylcarbinol Derivatives. ACS CENTRAL SCIENCE 2021; 7:1216-1224. [PMID: 34345671 PMCID: PMC8323246 DOI: 10.1021/acscentsci.1c00460] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2021] [Indexed: 05/27/2023]
Abstract
Polymers that release functional small molecules in response to mechanical force are appealing targets for drug delivery, sensing, catalysis, and many other applications. Mechanically sensitive molecules called mechanophores are uniquely suited to enable molecular release with excellent selectivity and control, but mechanophore designs capable of releasing cargo with diverse chemical functionality are limited. Here, we describe a general and highly modular mechanophore platform based on masked 2-furylcarbinol derivatives that spontaneously decompose under mild conditions upon liberation via a mechanically triggered reaction, resulting in the release of a covalently installed molecular payload. We identify key structure-property relationships for the reactivity of 2-furylcarbinol derivatives that enable the mechanically triggered release of functionally diverse molecular cargo with release kinetics being tunable over several orders of magnitude. In particular, the incorporation of an electron-donating phenoxy group on the furan ring in combination with an α-methyl substituent dramatically lowers the activation barrier for fragmentation, providing a highly active substrate for molecular release. Moreover, we find that phenoxy substitution enhances the thermal stability of the mechanophore without adversely affecting its mechanochemical reactivity. The generality and efficacy of this molecular design platform are demonstrated using ultrasound-induced mechanical force to trigger the efficient release of a broad scope of cargo molecules, including those bearing alcohol, phenol, alkylamine, arylamine, carboxylic acid, and sulfonic acid functional groups.
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Affiliation(s)
- Xiaoran Hu
- Division of Chemistry and Chemical
Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Tian Zeng
- Division of Chemistry and Chemical
Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Corey C. Husic
- Division of Chemistry and Chemical
Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Maxwell J. Robb
- Division of Chemistry and Chemical
Engineering, California Institute of Technology, Pasadena, California 91125, United States
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34
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Kida J, Aoki D, Otsuka H. Self-Strengthening of Cross-Linked Elastomers via the Use of Dynamic Covalent Macrocyclic Mechanophores. ACS Macro Lett 2021; 10:558-563. [PMID: 35570767 DOI: 10.1021/acsmacrolett.1c00124] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The creation of polymeric materials that self-strengthen in response to a mechanical force is an important objective in the field of polymer chemistry. Here, the mechanochemical strengthening of cross-linked elastomers using macrocyclic mechanophores that contain a dynamic covalent disulfide bond is reported. Cross-linked poly(hexyl methacrylate) (CPHMA) polymers with macrocyclic mechanophores inserted at the cross-linking points were synthesized via free radical polymerization. Tensile and swelling tests showed that the addition of the macrocyclic mechanophores to the CPHMA polymers successfully impart them with self-strengthening functionality following compression, without the need for any additives such as monomers and modifiers, or any other stimuli.
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35
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Bowser BH, Wang S, Kouznetsova TB, Beech HK, Olsen BD, Rubinstein M, Craig SL. Single-Event Spectroscopy and Unravelling Kinetics of Covalent Domains Based on Cyclobutane Mechanophores. J Am Chem Soc 2021; 143:5269-5276. [PMID: 33783187 DOI: 10.1021/jacs.1c02149] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Mechanochemical reactions that lead to an increase in polymer contour length have the potential to serve as covalent synthetic mimics of the mechanical unfolding of noncovalent "stored length" domains in structural proteins. Here we report the force-dependent kinetics of stored length release in a family of covalent domain polymers based on cis-1,2-substituted cyclobutane mechanophores. The stored length is determined by the size (n) of a fused ring in an [n.2.0] bicyclic architecture, and it can be made sufficiently large (>3 nm per event) that individual unravelling events are resolved in both constant-velocity and constant-force single-molecule force spectroscopy (SMFS) experiments. Replacing a methylene in the pulling attachment with a phenyl group drops the force necessary to achieve rate constants of 1 s-1 from ca. 1970 pN (dialkyl handles) to 630 pN (diaryl handles), and the substituent effect is attributed to a combination of electronic stabilization and mechanical leverage effects. In contrast, the kinetics are negligibly perturbed by changes in the amount of stored length. The independent control of unravelling force and extension holds promise as a probe of molecular behavior in polymer networks and for optimizing the behaviors of materials made from covalent domain polymers.
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Affiliation(s)
- Brandon H Bowser
- NSF Center for the Chemistry of Molecularly Optimized Networks, Duke University, Durham, North Carolina 27708, United States.,Department of Chemistry, Duke University, Durham, North Carolina 27708, United States
| | - Shu Wang
- NSF Center for the Chemistry of Molecularly Optimized Networks, Duke University, Durham, North Carolina 27708, United States.,Department of Chemistry, Duke University, Durham, North Carolina 27708, United States
| | - Tatiana B Kouznetsova
- NSF Center for the Chemistry of Molecularly Optimized Networks, Duke University, Durham, North Carolina 27708, United States.,Department of Chemistry, Duke University, Durham, North Carolina 27708, United States
| | - Haley K Beech
- NSF Center for the Chemistry of Molecularly Optimized Networks, Duke University, Durham, North Carolina 27708, United States.,Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Bradley D Olsen
- NSF Center for the Chemistry of Molecularly Optimized Networks, Duke University, Durham, North Carolina 27708, United States.,Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Michael Rubinstein
- NSF Center for the Chemistry of Molecularly Optimized Networks, Duke University, Durham, North Carolina 27708, United States.,Department of Chemistry, Duke University, Durham, North Carolina 27708, United States.,Departments of Physics, Mechanical Engineering and Materials Science, and Biomedical Engineering, Duke University, Durham, North Carolina 27708, United States.,World Premier Institute for Chemical Reaction Design and Discovery, Hokkaido University, Sapporo, Japan
| | - Stephen L Craig
- NSF Center for the Chemistry of Molecularly Optimized Networks, Duke University, Durham, North Carolina 27708, United States.,Department of Chemistry, Duke University, Durham, North Carolina 27708, United States
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36
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Wang S, Beech HK, Bowser BH, Kouznetsova TB, Olsen BD, Rubinstein M, Craig SL. Mechanism Dictates Mechanics: A Molecular Substituent Effect in the Macroscopic Fracture of a Covalent Polymer Network. J Am Chem Soc 2021; 143:3714-3718. [PMID: 33651599 DOI: 10.1021/jacs.1c00265] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The fracture of rubbery polymer networks involves a series of molecular events, beginning with conformational changes along the polymer backbone and culminating with a chain scission reaction. Here, we report covalent polymer gels in which the macroscopic fracture "reaction" is controlled by mechanophores embedded within mechanically active network strands. We synthesized poly(ethylene glycol) (PEG) gels through the end-linking of azide-terminated tetra-arm PEG (Mn = 5 kDa) with bis-alkyne linkers. Networks were formed under identical conditions, except that the bis-alkyne was varied to include either a cis-diaryl (1) or cis-dialkyl (2) linked cyclobutane mechanophore that acts as a mechanochemical "weak link" through a force-coupled cycloreversion. A control network featuring a bis-alkyne without cyclobutane (3) was also synthesized. The networks show the same linear elasticity (G' = 23-24 kPa, 0.1-100 Hz) and equilibrium mass swelling ratios (Q = 10-11 in tetrahydrofuran), but they exhibit tearing energies that span a factor of 8 (3.4 J, 10.6, and 27.1 J·m-2 for networks with 1, 2, and 3, respectively). The difference in fracture energy is well-aligned with the force-coupled scission kinetics of the mechanophores observed in single-molecule force spectroscopy experiments, implicating local resonance stabilization of a diradical transition state in the cycloreversion of 1 as a key determinant of the relative ease with which its network is torn. The connection between macroscopic fracture and a small-molecule reaction mechanism suggests opportunities for molecular understanding and optimization of polymer network behavior.
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Affiliation(s)
| | - Haley K Beech
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | | | | | - Bradley D Olsen
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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37
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Kumar S, Stauch T. The activation efficiency of mechanophores can be modulated by adjacent polymer composition. RSC Adv 2021; 11:7391-7396. [PMID: 35423252 PMCID: PMC8695044 DOI: 10.1039/d0ra09834e] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2020] [Accepted: 02/05/2021] [Indexed: 11/21/2022] Open
Abstract
The activation efficiency of mechanophores in stress-responsive polymers is generally limited by the competing process of unspecific scission in other parts of the polymer chain. Here it is shown that the linker between the mechanophore and the polymer backbone determines the force required to activate the mechanophore. Using quantum chemical methods, it is demonstrated that the activation forces of three mechanophores (Dewar benzene, benzocyclobutene and gem-dichlorocyclopropane) can be adjusted over a range of almost 300% by modifying the chemical composition of the linker. The results are discussed in terms of changes in electron density, strain distribution and structural parameters during the rupture process. Using these findings it is straightforward to either significantly enhance or reduce the activation rate of mechanophores in stress-responsive materials, depending on the desired use case. The methodology is applied to switch a one-step "gating" of a mechanochemical transformation to a two-step process.
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Affiliation(s)
- Sourabh Kumar
- University of Bremen, Institute for Physical and Theoretical Chemistry Leobener Straße NW2 D-28359 Bremen Germany
| | - Tim Stauch
- University of Bremen, Institute for Physical and Theoretical Chemistry Leobener Straße NW2 D-28359 Bremen Germany
- Bremen Center for Computational Materials Science, University of Bremen Am Fallturm 1 D-28359 Bremen Germany
- MAPEX Center for Materials and Processes, University of Bremen Bibliothekstraße 1 D-28359 Bremen Germany
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38
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O’Neill RT, Boulatov R. The many flavours of mechanochemistry and its plausible conceptual underpinnings. Nat Rev Chem 2021; 5:148-167. [PMID: 37117533 DOI: 10.1038/s41570-020-00249-y] [Citation(s) in RCA: 131] [Impact Index Per Article: 43.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/23/2020] [Indexed: 12/12/2022]
Abstract
Mechanochemistry describes diverse phenomena in which mechanical load affects chemical reactivity. The fuzziness of this definition means that it includes processes as seemingly disparate as motor protein function, organic synthesis in a ball mill, reactions at a propagating crack, chemical actuation, and polymer fragmentation in fast solvent flows and in mastication. In chemistry, the rate of a reaction in a flask does not depend on how fast the flask moves in space. In mechanochemistry, the rate at which a material is deformed affects which and how many bonds break. In other words, in some manifestations of mechanochemistry, macroscopic motion powers otherwise endergonic reactions. In others, spontaneous chemical reactions drive mechanical motion. Neither requires thermal or electrostatic gradients. Distinct manifestations of mechanochemistry are conventionally treated as being conceptually independent, which slows the field in its transformation from being a collection of observations to a rigorous discipline. In this Review, we highlight observations suggesting that the unifying feature of mechanochemical phenomena may be the coupling between inertial motion at the microscale to macroscale and changes in chemical bonding enabled by transient build-up and relaxation of strains, from macroscopic to molecular. This dynamic coupling across multiple length scales and timescales also greatly complicates the conceptual understanding of mechanochemistry.
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39
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Razgoniaev AO, Glasstetter LM, Kouznetsova TB, Hall KC, Horst M, Craig SL, Franz KJ. Single-Molecule Activation and Quantification of Mechanically Triggered Palladium-Carbene Bond Dissociation. J Am Chem Soc 2021; 143:1784-1789. [PMID: 33480680 DOI: 10.1021/jacs.0c13219] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Metal-complexed N-heterocyclic carbene (NHC) mechanophores are latent reactants and catalysts for a range of mechanically driven chemical responses, but mechanochemical scission of the metal-NHC bond has not been experimentally characterized. Here we report the single-molecule force spectroscopy of ligand dissociation from a pincer NHC-pyridine-NHC Pd(II) complex. The force-coupled rate constant for ligand dissociation reaches 50 s-1 at forces of approximately 930 pN. Experimental and computational observations support a dissociative, rather than associative, mechanism of ligand displacement, with rate-limiting scission of the Pd-NHC bond followed by rapid dissociation of the pyridine moiety from Pd.
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Affiliation(s)
- Anton O Razgoniaev
- Department of Chemistry, Duke University, Durham, North Carolina 27708, United States
| | - Logan M Glasstetter
- Department of Chemistry, Duke University, Durham, North Carolina 27708, United States
| | - Tatiana B Kouznetsova
- Department of Chemistry, Duke University, Durham, North Carolina 27708, United States
| | - Kacey C Hall
- Department of Chemistry, Duke University, Durham, North Carolina 27708, United States
| | - Matias Horst
- Department of Chemistry, Duke University, Durham, North Carolina 27708, United States
| | - Stephen L Craig
- Department of Chemistry, Duke University, Durham, North Carolina 27708, United States
| | - Katherine J Franz
- Department of Chemistry, Duke University, Durham, North Carolina 27708, United States
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40
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Chen Y, Mellot G, van Luijk D, Creton C, Sijbesma RP. Mechanochemical tools for polymer materials. Chem Soc Rev 2021; 50:4100-4140. [DOI: 10.1039/d0cs00940g] [Citation(s) in RCA: 112] [Impact Index Per Article: 37.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
This review aims to provide a field guide for the implementation of mechanochemistry in synthetic polymers by summarizing the molecules, materials, and methods that have been developed in this field.
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Affiliation(s)
- Yinjun Chen
- Department of Chemical Engineering & Chemistry and Institute for Complex Molecular Systems
- Eindhoven University of Technology
- 5600 MB Eindhoven
- The Netherlands
| | - Gaëlle Mellot
- Laboratoire Sciences et Ingénierie de la Matière Molle
- ESPCI Paris
- PSL University
- Sorbonne Université
- CNRS
| | - Diederik van Luijk
- Department of Chemical Engineering & Chemistry and Institute for Complex Molecular Systems
- Eindhoven University of Technology
- 5600 MB Eindhoven
- The Netherlands
| | - Costantino Creton
- Laboratoire Sciences et Ingénierie de la Matière Molle
- ESPCI Paris
- PSL University
- Sorbonne Université
- CNRS
| | - Rint P. Sijbesma
- Department of Chemical Engineering & Chemistry and Institute for Complex Molecular Systems
- Eindhoven University of Technology
- 5600 MB Eindhoven
- The Netherlands
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41
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Wu M, Guo Z, He W, Yuan W, Chen Y. Empowering self-reporting polymer blends with orthogonal optical properties responsive in a broader force range. Chem Sci 2020; 12:1245-1250. [PMID: 34163886 PMCID: PMC8179123 DOI: 10.1039/d0sc06140a] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Self-reporting polymers, which can indicate damage with perceptible optical signals in a tailored force range, are useful as stress-sensitive sensors. We demonstrate a simple approach to realize this function by embedding two distinct mechanophores - rhodamine (Rh) and bis(adamantyl)-1,2-dioxetane (Ad), in polyurethane/polylactic acid blends. The deformed blends generate red coloration and red chemiluminescence. Such a unique dual-responsive behavior was evaluated by solid-state UV-vis spectroscopy, macroscopic tensile tests with in situ RGB and light intensity analyses, which supported a stress-correlated occurrence of the ring-opening of Rh, the scission of Ad and the fluorescence resonance energy transfer process between the respective mechanochemical species. Complementarity stemming from the difference in properties and manifestations of the two mechanophores is essential. That is, the more labile Rh allows shifting the appreciable optical changes to a much lower force threshold; the transient nature and high dynamic range of mechanochemiluminescence from Ad map in real time where and when many of the covalently incorporated dioxetane bonds break; besides, the disrupted yet non-scissile structure of Rh acts as a fluorescent acceptor to effectively harvest chemiluminescence from ruptured Ad. The current strategy is thus empowering multi-functional mechano-responsive polymers with greatly improved sensitivity and resolution for multimodal stress reporting.
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Affiliation(s)
- Mengjiao Wu
- Department of Chemistry, Key Laboratory of Mechanism Theory and Equipment Design of State Ministry of Education, Tianjin University Tianjin 300354 China
| | - Zhen Guo
- Department of Chemistry, Key Laboratory of Mechanism Theory and Equipment Design of State Ministry of Education, Tianjin University Tianjin 300354 China
| | - Weiye He
- Department of Chemistry, Key Laboratory of Mechanism Theory and Equipment Design of State Ministry of Education, Tianjin University Tianjin 300354 China
| | - Wei Yuan
- Department of Chemistry, Key Laboratory of Mechanism Theory and Equipment Design of State Ministry of Education, Tianjin University Tianjin 300354 China
| | - Yulan Chen
- Department of Chemistry, Key Laboratory of Mechanism Theory and Equipment Design of State Ministry of Education, Tianjin University Tianjin 300354 China
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42
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Martínez‐Tong DE, Pomposo JA, Verde‐Sesto E. Triggering Forces at the Nanoscale: Technologies for Single‐Chain Mechanical Activation and Manipulation. Macromol Rapid Commun 2020; 42:e2000654. [DOI: 10.1002/marc.202000654] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Revised: 11/14/2020] [Indexed: 01/05/2023]
Affiliation(s)
- Daniel E. Martínez‐Tong
- Departamento de Polímeros y Materiales Avanzados: Física, Química y Tecnología University of the Basque Country (UPV/EHU) P. Manuel Lardizábal 3 Donostia‐San Sebastián 20018 Spain
- Centro de Física de Materiales (UPV/EHU‐CSIC) P. Manuel Lardizábal 5 San Sebastián 20018 Spain
| | - José A. Pomposo
- Departamento de Polímeros y Materiales Avanzados: Física, Química y Tecnología University of the Basque Country (UPV/EHU) P. Manuel Lardizábal 3 Donostia‐San Sebastián 20018 Spain
- Centro de Física de Materiales (CFM) (CSIC‐UPV/EHU)—Materials Physics Center (MPC) Paseo Manuel de Lardizábal 5 Donostia‐San Sebastián 20018 Spain
- IKERBASQUE—Basque Foundation for Science Plaza Euskadi 5 Bilbao 48009 Spain
| | - Ester Verde‐Sesto
- Centro de Física de Materiales (CFM) (CSIC‐UPV/EHU)—Materials Physics Center (MPC) Paseo Manuel de Lardizábal 5 Donostia‐San Sebastián 20018 Spain
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43
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Pan Y, Zhang H, Xu P, Tian Y, Wang C, Xiang S, Boulatov R, Weng W. A Mechanochemical Reaction Cascade for Controlling Load-Strengthening of a Mechanochromic Polymer. Angew Chem Int Ed Engl 2020; 59:21980-21985. [PMID: 32827332 PMCID: PMC7756483 DOI: 10.1002/anie.202010043] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Indexed: 11/08/2022]
Abstract
We demonstrate an intermolecular reaction cascade to control the force which triggers crosslinking of a mechanochromic polymer of spirothiopyran (STP). Mechanochromism arises from rapid reversible force-sensitive isomerization of STP to a merocyanine, which reacts rapidly with activated C=C bonds. The concentration of such bonds, and hence the crosslinking rate, is controlled by force-dependent dissociation of a Diels-Alder adduct of anthracene and maleimide. Because the adduct requires ca. 1 nN higher force to dissociate at the same rate as that of STP isomerization, the cascade limits crosslinking to overstressed regions of the material, which are at the highest rate of material damage. Using comb polymers decreased the minimum concentration of mechanophores required to crosslinking by about 100-fold compared to previous examples of load-strengthening materials. The approach described has potential for controlling a broad range of reaction sequences triggered by mechanical load.
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Affiliation(s)
- Yifei Pan
- Department of ChemistryCollege of Chemistry and Chemical EngineeringXiamen University422 South Siming RoadXiamenFujian361005P. R. China
| | - Huan Zhang
- Department of ChemistryCollege of Chemistry and Chemical EngineeringXiamen University422 South Siming RoadXiamenFujian361005P. R. China
| | - Piaoxue Xu
- Department of ChemistryCollege of Chemistry and Chemical EngineeringXiamen University422 South Siming RoadXiamenFujian361005P. R. China
| | - Yancong Tian
- Department of ChemistryUniversity of Liverpool and Donnan LabG31, Crown St.LiverpoolL69 7ZDUK
| | - Chenxu Wang
- Department of ChemistryUniversity of Liverpool and Donnan LabG31, Crown St.LiverpoolL69 7ZDUK
| | - Shishuai Xiang
- Department of ChemistryCollege of Chemistry and Chemical EngineeringXiamen University422 South Siming RoadXiamenFujian361005P. R. China
| | - Roman Boulatov
- Department of ChemistryUniversity of Liverpool and Donnan LabG31, Crown St.LiverpoolL69 7ZDUK
| | - Wengui Weng
- Department of ChemistryCollege of Chemistry and Chemical EngineeringXiamen University422 South Siming RoadXiamenFujian361005P. R. China
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44
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Tian Y, Cao X, Li X, Zhang H, Sun CL, Xu Y, Weng W, Zhang W, Boulatov R. A Polymer with Mechanochemically Active Hidden Length. J Am Chem Soc 2020; 142:18687-18697. [PMID: 33064473 PMCID: PMC7596784 DOI: 10.1021/jacs.0c09220] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Incorporating hidden length into polymer chains can improve their mechanical properties, because release of the hidden length under mechanical loads enables localized strain relief without chain fracture. To date, the design of hidden length has focused primarily on the choice of the sacrificial bonds holding the hidden length together. Here we demonstrate the advantages of adding mechanochemical reactivity to hidden length itself, using a new mechanophore that integrates (Z)-2,3-diphenylcyclobutene-1,4-dicarboxylate, with hitherto unknown mechanochemistry, into macrocyclic cinnamate dimers. Stretching a polymer of this mechanophore more than doubles the chain contour length without fracture. DFT calculations indicate that the sequential dissociation of the dimer, followed by cyclobutene isomerization at higher forces yields a chain fracture energy 11 times that of a simple polyester of the same initial contour length and preserves high energy-dissipating capacity up to ∼3 nN. In sonicated solutions cyclobutene isomerizes to two distinct products by competing reaction paths, validating the computed mechanochemical mechanism and suggesting an experimental approach to quantifying the distribution of single-chain forces under diverse loading scenarios.
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Affiliation(s)
- Yancong Tian
- Department of Chemistry, University of Liverpool, Crown Street, Liverpool L69 7ZD, U.K
| | - Xiaodong Cao
- Department of Chemistry, College of Chemistry and Engineering, Xiamen University, Xiamen, Fujian 361005, People's Republic of China
| | - Xun Li
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, Jilin 130012, People's Republic of China
| | - Huan Zhang
- Department of Chemistry, College of Chemistry and Engineering, Xiamen University, Xiamen, Fujian 361005, People's Republic of China
| | - Cai-Li Sun
- Department of Chemistry, University of Liverpool, Crown Street, Liverpool L69 7ZD, U.K
| | - Yuanze Xu
- Department of Chemistry, College of Chemistry and Engineering, Xiamen University, Xiamen, Fujian 361005, People's Republic of China
| | - Wengui Weng
- Department of Chemistry, College of Chemistry and Engineering, Xiamen University, Xiamen, Fujian 361005, People's Republic of China
| | - Wenke Zhang
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, Jilin 130012, People's Republic of China
| | - Roman Boulatov
- Department of Chemistry, University of Liverpool, Crown Street, Liverpool L69 7ZD, U.K
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45
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Pan Y, Zhang H, Xu P, Tian Y, Wang C, Xiang S, Boulatov R, Weng W. A Mechanochemical Reaction Cascade for Controlling Load‐Strengthening of a Mechanochromic Polymer. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.202010043] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- Yifei Pan
- Department of Chemistry College of Chemistry and Chemical Engineering Xiamen University 422 South Siming Road Xiamen Fujian 361005 P. R. China
| | - Huan Zhang
- Department of Chemistry College of Chemistry and Chemical Engineering Xiamen University 422 South Siming Road Xiamen Fujian 361005 P. R. China
| | - Piaoxue Xu
- Department of Chemistry College of Chemistry and Chemical Engineering Xiamen University 422 South Siming Road Xiamen Fujian 361005 P. R. China
| | - Yancong Tian
- Department of Chemistry University of Liverpool and Donnan Lab G31, Crown St. Liverpool L69 7ZD UK
| | - Chenxu Wang
- Department of Chemistry University of Liverpool and Donnan Lab G31, Crown St. Liverpool L69 7ZD UK
| | - Shishuai Xiang
- Department of Chemistry College of Chemistry and Chemical Engineering Xiamen University 422 South Siming Road Xiamen Fujian 361005 P. R. China
| | - Roman Boulatov
- Department of Chemistry University of Liverpool and Donnan Lab G31, Crown St. Liverpool L69 7ZD UK
| | - Wengui Weng
- Department of Chemistry College of Chemistry and Chemical Engineering Xiamen University 422 South Siming Road Xiamen Fujian 361005 P. R. China
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46
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Affiliation(s)
- Guillaume De Bo
- Department of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
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47
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Klein IM, Husic CC, Kovács DP, Choquette NJ, Robb MJ. Validation of the CoGEF Method as a Predictive Tool for Polymer Mechanochemistry. J Am Chem Soc 2020; 142:16364-16381. [DOI: 10.1021/jacs.0c06868] [Citation(s) in RCA: 62] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- Isabel M. Klein
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Corey C. Husic
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Dávid P. Kovács
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Nicolas J. Choquette
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Maxwell J. Robb
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
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48
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Zhang Y, Lund E, Gossweiler GR, Lee B, Niu Z, Khripin C, Munch E, Couty M, Craig SL. Molecular Damage Detection in an Elastomer Nanocomposite with a Coumarin Dimer Mechanophore. Macromol Rapid Commun 2020; 42:e2000359. [PMID: 32761960 DOI: 10.1002/marc.202000359] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2020] [Revised: 07/27/2020] [Indexed: 12/12/2022]
Abstract
Molecular force probes that generate optical responses to critical levels of mechanical stress (mechanochromophores) are increasingly attractive tools for identifying molecular sites that are most prone to failure. Here, a coumarin dimer mechanophore whose mechanical strength is comparable to that of the sulfur-sulfur bonds found in vulcanized rubbers is reported. It is further shown that the strain-induced scission of the coumarin dimer within the matrix of a particle-reinforced polybutadiene-based co-polymer can be detected and quantified by fluorescence spectroscopy, when cylinders of the nanocomposite are subjected to unconstrained uniaxial stress. The extent of the scission suggests that the coumarin dimers are molecular "weak links" within the matrix, and, by analogy, sulfur bridges are likely to be the same in vulcanized rubbers. The mechanophore is embedded in polymer main chains, grafting agent, and cross-linker positions in a polymer composite in order to generate experimental data to understand how macroscopic mechanical stress is transferred at the molecular scale especially in highly entangled cross-linked polymer nanocomposite. Finally, the extent of activation is enhanced by approximately an order of magnitude by changing the regiochemistry and stereochemistry of the coumarin dimer and embedding the mechanophore at the heterointerface of the particle-reinforced elastomer.
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Affiliation(s)
- Yudi Zhang
- Department of Chemistry, Duke University, Durham, NC, 27708, USA
| | - Ethen Lund
- Department of Mechanical Engineering and Materials Science, Yale University, New Haven, CT, 06511, USA
| | | | - Bobin Lee
- Department of Chemistry, Duke University, Durham, NC, 27708, USA
| | - Zhenbin Niu
- Department of Chemistry, Duke University, Durham, NC, 27708, USA
| | | | - Etienne Munch
- Manufacture Française des Pneumatiques Michelin, 23, Place des Carmes Dechaux, 63000, Clermont-Ferrand, France
| | - Marc Couty
- Manufacture Française des Pneumatiques Michelin, 23, Place des Carmes Dechaux, 63000, Clermont-Ferrand, France
| | - Stephen L Craig
- Department of Chemistry, Duke University, Durham, NC, 27708, USA
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49
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Sha Y, Jia H, Shen Z, Luo Z. Synthetic strategies, properties, and applications of unsaturated main-chain metallopolymers prepared by olefin metathesis polymerization. POLYM REV 2020. [DOI: 10.1080/15583724.2020.1801727] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Ye Sha
- Department of Chemistry and Material Science, College of Science, Nanjing Forestry University, Nanjing, PR China
| | - Huan Jia
- Department of Chemistry and Material Science, College of Science, Nanjing Forestry University, Nanjing, PR China
| | - Zhihua Shen
- Department of Chemistry and Material Science, College of Science, Nanjing Forestry University, Nanjing, PR China
| | - Zhenyang Luo
- Department of Chemistry and Material Science, College of Science, Nanjing Forestry University, Nanjing, PR China
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50
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Abstract
Mechanophores (mechanoresponsive molecules) offer great promises for the development of smart force-responsive materials. The activity of a mechanophore can be tuned by altering its structure or the composition of the actuating polymer. Here we show that a [2]catenane can act as a mechanical protecting group by diverting tensional forces away from a mechanically active functional group embedded in one of its rings. This property emerges from the mobility of the two rings of the catenane, which are able to rotate along each other until the tension equalizes over the entirety of the catenated framework. This approach provides a new way to control the mechanical activity of a mechanophore.
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Affiliation(s)
- Min Zhang
- Department of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
| | - Guillaume De Bo
- Department of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
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