1
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Hertel R, Raisch M, Walter M, Reiter G, Sommer M. Mechanistically Different Mechanochromophores Enable Calibration and Validation of Molecular Forces in Glassy Polymers and Elastomeric Networks. Angew Chem Int Ed Engl 2024:e202409369. [PMID: 39136230 DOI: 10.1002/anie.202409369] [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: 05/17/2024] [Indexed: 10/18/2024]
Abstract
Sterically distorted donor-acceptor π-systems, termed DA springs, can be progressively planarized under mechanical load causing a bathochromic shift of the photoluminescence (PL) spectrum. By combining theory and experiment, we here use a simple linear force calibration for two different conformational mechanochromophores to determine molecular forces in polymers from the mechanochromic shift in PL wavelength during multiple uniaxial tensile tests. Two systems are used, i) a highly entangled linear glassy polyphenylene and ii) a covalent elastomeric polydimethylsiloxane network. The mean forces estimated by this method are validated using known threshold forces for the mechanochemical ring-opening reactions of two different spiropyran force probes. The agreement between both approaches underlines that these DA springs provide the unique opportunity for the online monitoring of local molecular forces present in diverse polymer matrices.
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Affiliation(s)
- Raphael Hertel
- Department of Polymer Chemistry, Institute for Chemistry, Chemnitz University of Technology, Str. der Nationen 62, 09111, Chemnitz, Germany
| | - Maximilian Raisch
- Department of Polymer Chemistry, Institute for Chemistry, Chemnitz University of Technology, Str. der Nationen 62, 09111, Chemnitz, Germany
| | - Michael Walter
- FIT Freiburg Center for Interactive Materials and Bioinspired Technologies, Albert-Ludwig-University of Freiburg, Georges-Köhler-Allee 105, 79110, Freiburg, Germany
| | - Günter Reiter
- Institute of Physics, Albert-Ludwig-University of Freiburg, Hermann-Herder-Str. 3, 79104, Freiburg, Germany
| | - Michael Sommer
- Department of Polymer Chemistry, Institute for Chemistry, Chemnitz University of Technology, Str. der Nationen 62, 09111, Chemnitz, Germany
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2
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Gupta R, Verma SD. Two-Dimensional Fluctuation Correlation Spectroscopy (2D-FlucCS): A Method to Determine the Origin of Relaxation Rate Dispersion. ACS MEASUREMENT SCIENCE AU 2024; 4:153-162. [PMID: 38645580 PMCID: PMC11027202 DOI: 10.1021/acsmeasuresciau.3c00048] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/01/2023] [Revised: 01/11/2024] [Accepted: 01/11/2024] [Indexed: 04/23/2024]
Abstract
Relaxation rate dispersion, i.e., nonexponential or multicomponent kinetics, is observed in complex systems when measuring relaxation kinetics. Often, the origin of rate dispersion is associated with the heterogeneity in the system. However, both homogeneous (where all molecules experience the same rate but inherently nonexponential) and heterogeneous (where all molecules experience different rates) systems can exhibit rate dispersion. A multidimensional correlation analysis method has been demonstrated to detect and quantify rate dispersion observed in molecular rotation, diffusion, solvation, and reaction kinetics. One-dimensional (1D) autocorrelation function detects rate dispersion and measures its extent. Two-dimensional (2D) autocorrelation function measures the origin of rate dispersion and distinguishes homogeneous from heterogeneous. In a heterogeneous system, implicitly there exist subensembles of molecules experiencing different rates. A three-dimensional (3D) autocorrelation function measures subensemble exchange if present and reveals if the system possesses static or dynamic heterogeneity. This perspective discusses the principles, applications, and potential and also presents a future outlook of two-dimensional fluctuation correlation spectroscopy (2D-FlucCS). The method is applicable to any experiment or simulation where a time series of fluctuation in an observable (emission, scattering, current, etc.) around a mean value can be obtained in steady state (equilibrium or nonequilibrium), provided the system is ergodic.
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Affiliation(s)
- Ruchir Gupta
- Spectroscopy and Dynamics
Visualization Laboratory, Department of Chemistry, Indian Institute of Science Education and Research Bhopal, Bhauri, Bhopal 462066, Madhya Pradesh, India
| | - Sachin Dev Verma
- Spectroscopy and Dynamics
Visualization Laboratory, Department of Chemistry, Indian Institute of Science Education and Research Bhopal, Bhauri, Bhopal 462066, Madhya Pradesh, India
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3
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Huo Z, Watkins KF, Jeong BC, Statt A, Laaser JE. Preferential Mechanochemical Activation of Short Chains in Bidisperse Triblock Elastomers. ACS Macro Lett 2023; 12:1213-1217. [PMID: 37619531 PMCID: PMC10515626 DOI: 10.1021/acsmacrolett.3c00366] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2023] [Accepted: 08/18/2023] [Indexed: 08/26/2023]
Abstract
Polymer mechanochemistry offers attractive opportunities for using macroscopic forces to drive molecular-scale chemical transformations, but achieving efficient activation in bulk polymeric materials has remained challenging. Understanding how the structure and topology of polymer networks impact molecular-scale force distributions is critical for addressing this problem. Here we show that in block copolymer elastomers the molecular-scale force distributions and mechanochemical activation yields are strongly impacted by the molecular weight distribution of the polymers. We prepare bidisperse triblock copolymer elastomers with spiropyran mechanophores placed in either the short chains, the long chains, or both and show that the overall mechanochemical activation of the materials is dominated by the short chains. Molecular dynamics simulations reveal that this preferential activation occurs because pinning of the ends of the elastically effective midblocks to the glassy/rubbery interface forces early extension of the short chains. These results suggest that microphase segregation and network strand dispersity play a critical role in determining molecular-scale force distributions and suggest that selective placement of mechanophores in microphase-segregated polymers is a promising design strategy for efficient mechanochemical activation in bulk materials.
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Affiliation(s)
- Zijian Huo
- Department
of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Kasey F. Watkins
- Department
of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Brandon C. Jeong
- Department
of Chemical and Biomolecular Engineering, University of Illinois, Urbana−Champaign, Illinois 61801, United States
| | - Antonia Statt
- Department
of Chemical and Biomolecular Engineering, University of Illinois, Urbana−Champaign, Illinois 61801, United States
- Department
of Materials Science and Engineering, University
of Illinois, Urbana−Champaign, Illinois 61801, United States
| | - Jennifer E. Laaser
- Department
of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
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4
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Clough JM, Kilchoer C, Wilts BD, Weder C. Hierarchically Structured Deformation-Sensing Mechanochromic Pigments. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2023; 10:e2206416. [PMID: 36935363 PMCID: PMC10161078 DOI: 10.1002/advs.202206416] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2022] [Revised: 02/23/2023] [Indexed: 05/06/2023]
Abstract
Mechanochromic materials alter their color in response to mechanical force and are useful for both fundamental studies and practical applications. Several approaches are used to render polymers mechanochromic, but they generally suffer from limitations in sensing range, capacity to provide quantitative information, and their capability to enable broad and simple implementation. Here, is it reported that these problems can be overcome by combining photonic structures, which alter their reflection upon deformation, with covalent mechanophores, whose spectral properties change upon mechanically induced bond scission, in hierarchically structured mechanochromic pigments. This is achieved by synthesizing microspheres consisting of an elastic polymer with spiropyran-based cross-links and non-close-packed silica nanoparticles. A strain of less than 1% can be detected in a shift of the reflection band from the photonic structure, while the onset strain for the conversion of the spiropyran into fluorescent merocyanine ranges from 30% to 70%, creating a broad strain detection range. The two responses are tailorable and synergistic, permitting the activation strain for the mechanophore response to be tuned. The mechano-sensing photonic pigments are demonstrated to be readily incorporated into different polymeric materials of interest and quantitatively probe spatially heterogeneous deformations over a large strain range.
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Affiliation(s)
- Jess M Clough
- Adolphe Merkle Institute, University of Fribourg, Chemin des Verdiers 4, Fribourg, 1700, Switzerland
| | - Cédric Kilchoer
- Adolphe Merkle Institute, University of Fribourg, Chemin des Verdiers 4, Fribourg, 1700, Switzerland
| | - Bodo D Wilts
- Adolphe Merkle Institute, University of Fribourg, Chemin des Verdiers 4, Fribourg, 1700, Switzerland
- Chemistry and Physics of Materials, University of Salzburg, Jakob-Haringer-Strasse 2a, Salzburg, 5020, Austria
| | - Christoph Weder
- Adolphe Merkle Institute, University of Fribourg, Chemin des Verdiers 4, Fribourg, 1700, Switzerland
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5
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Huo Z, Arora S, Kong VA, Myrga BJ, Statt A, Laaser JE. Effect of Polymer Composition and Morphology on Mechanochemical Activation in Nanostructured Triblock Copolymers. Macromolecules 2023; 56:1845-1854. [PMID: 36938512 PMCID: PMC10018773 DOI: 10.1021/acs.macromol.2c02475] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2022] [Revised: 02/07/2023] [Indexed: 03/06/2023]
Abstract
The effect of composition and morphology on mechanochemical activation in nanostructured block copolymers was investigated in a series of poly(methyl methacrylate)-block-poly(n-butyl acrylate)-block-poly(methyl methacrylate) (PMMA-b-PnBA-b-PMMA) triblock copolymers containing a force-responsive spiropyran unit in the center of the rubbery PnBA midblock. Triblock copolymers with identical PnBA midblocks and varying lengths of PMMA end-blocks were synthesized from a spiropyran-containing macroinitiatior via atom transfer radical polymerization, yielding polymers with volume fractions of PMMA ranging from 0.21 to 0.50. Characterization by transmission electron microscopy revealed that the polymers self-assembled into spherical and cylindrical nanostructures. Simultaneous tensile tests and optical measurements revealed that mechanochemical activation is strongly correlated to the chemical composition and morphologies of the triblock copolymers. As the glassy (PMMA) block content is increased, the overall activation increases, and the onset of activation occurs at lower strain but higher stress, which agrees with predictions from our previous computational work. These results suggest that the self-assembly of nanostructured morphologies can play an important role in controlling mechanochemical activation in polymeric materials and provide insights into how polymer composition and morphology impact molecular-scale force distributions.
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Affiliation(s)
- Zijian Huo
- Department
of Chemistry, University of Pittsburgh, 219 Parkman Ave., Pittsburgh, Pennsylvania 15260, United States
| | - Swati Arora
- Department
of Chemistry, University of Pittsburgh, 219 Parkman Ave., Pittsburgh, Pennsylvania 15260, United States
| | - Victoria A. Kong
- Department
of Chemistry, University of Pittsburgh, 219 Parkman Ave., Pittsburgh, Pennsylvania 15260, United States
| | - Brandon J. Myrga
- Department
of Chemistry, University of Pittsburgh, 219 Parkman Ave., Pittsburgh, Pennsylvania 15260, United States
| | - Antonia Statt
- Materials
Science and Engineering, Grainger College of Engineering, University of Illinois, Urbana−Champaign, Illinois 61801, United States
| | - Jennifer E. Laaser
- Department
of Chemistry, University of Pittsburgh, 219 Parkman Ave., Pittsburgh, Pennsylvania 15260, United States
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6
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Ouchi T, Bowser BH, Kouznetsova TB, Zheng X, Craig SL. Strain-triggered acidification in a double-network hydrogel enabled by multi-functional transduction of molecular mechanochemistry. MATERIALS HORIZONS 2023; 10:585-593. [PMID: 36484385 DOI: 10.1039/d2mh01105k] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Recent work has demonstrated that force-triggered mechanochemical reactions within a polymeric material are capable of inducing measurable changes in macroscopic material properties, but examples of bulk property changes without irreversible changes in shape or structure are rare. Here, we report a double-network hydrogel that undergoes order-of-magnitude increases in acidity when strained, while recovering its initial shape after large deformation. The enabling mechanophore design is a 2-methoxy-gem-dichlorocyclopropane mechanoacid that is gated within a fused methyl methoxycyclobutene carboxylate mechanophore structure. This gated mechanoacid is incorporated via radical co-polymerization into linear and network polymers. Sonication experiments confirm the mechanical release of HCl, and single-molecule force spectroscopy reveals enhanced single-molecular toughness in the covalent strand. These mechanochemical functions are incorporated into a double-network hydrogel, leading to mechanically robust and thermally stable materials that undergo strain-triggered acid release. Both quasi-static stretching and high strain rate uniaxial compression result in substantial acidification of the hydrogel, from pH ∼ 7 to ∼5.
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Affiliation(s)
- Tetsu Ouchi
- Department of Chemistry, Duke University, Durham, North Carolina 27708, USA.
| | - Brandon H Bowser
- Department of Chemistry, Duke University, Durham, North Carolina 27708, USA.
| | | | - Xujun Zheng
- 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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7
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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: 20] [Impact Index Per Article: 20.0] [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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8
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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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9
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Shen H, Larsen MB, Roessler AG, Zimmerman PM, Boydston AJ. Mechanochemical Release of N-Heterocyclic Carbenes from Flex-Activated Mechanophores. Angew Chem Int Ed Engl 2021; 60:13559-13563. [PMID: 33826803 DOI: 10.1002/anie.202100576] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Revised: 03/25/2021] [Indexed: 11/09/2022]
Abstract
We have discovered a new flex-activated mechanophore that releases an N-heterocyclic carbene (NHC) under mechanical load. The mechanophore design is based upon NHC-carbodiimide (NHC-CDI) adducts and demonstrates an important first step toward flex-activated designs capable of further downstream reactivities. Since the flex-activation is non-destructive to the main polymer chains, the material can be subjected to multiple compression cycles to achieve iterative increases in the activation percentage of mechanophores. Two different NHC structures were demonstrated, signifying the potential modularity of the mechanophore design.
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Affiliation(s)
- Hang Shen
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, WI, 53706, USA
| | - Michael B Larsen
- Department of Materials Science and Engineering, Department of Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA.,Department of Chemistry, Western Washington University, Bellingham, WA, 98225, USA
| | - Allison G Roessler
- Department of Chemistry, University of Michigan, 930 N. University Ave, Ann Arbor, MI, 48109, USA.,Department of Chemistry, Oglethorpe University, 4484 Peachtree Rd, Atlanta, GA, 30319, USA
| | - Paul M Zimmerman
- Department of Chemistry, University of Michigan, 930 N. University Ave, Ann Arbor, MI, 48109, USA
| | - Andrew J Boydston
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, WI, 53706, USA.,Department of Materials Science and Engineering, Department of Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA.,Department of Chemistry, Western Washington University, Bellingham, WA, 98225, USA
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10
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Shen H, Larsen MB, Roessler AG, Zimmerman PM, Boydston AJ. Mechanochemical Release of
N
‐Heterocyclic Carbenes from Flex‐Activated Mechanophores. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202100576] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Hang Shen
- Department of Chemistry University of Wisconsin-Madison 1101 University Avenue Madison WI 53706 USA
| | - Michael B. Larsen
- Department of Materials Science and Engineering Department of Chemical and Biological Engineering University of Wisconsin-Madison Madison WI 53706 USA
- Department of Chemistry Western Washington University Bellingham WA 98225 USA
| | - Allison G. Roessler
- Department of Chemistry University of Michigan 930 N. University Ave Ann Arbor MI 48109 USA
- Department of Chemistry Oglethorpe University 4484 Peachtree Rd Atlanta GA 30319 USA
| | - Paul M. Zimmerman
- Department of Chemistry University of Michigan 930 N. University Ave Ann Arbor MI 48109 USA
| | - Andrew J. Boydston
- Department of Chemistry University of Wisconsin-Madison 1101 University Avenue Madison WI 53706 USA
- Department of Materials Science and Engineering Department of Chemical and Biological Engineering University of Wisconsin-Madison Madison WI 53706 USA
- Department of Chemistry Western Washington University Bellingham WA 98225 USA
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11
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Danielsen SPO, Beech HK, Wang S, El-Zaatari BM, Wang X, Sapir L, Ouchi T, Wang Z, Johnson PN, Hu Y, Lundberg DJ, Stoychev G, Craig SL, Johnson JA, Kalow JA, Olsen BD, Rubinstein M. Molecular Characterization of Polymer Networks. Chem Rev 2021; 121:5042-5092. [PMID: 33792299 DOI: 10.1021/acs.chemrev.0c01304] [Citation(s) in RCA: 60] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Polymer networks are complex systems consisting of molecular components. Whereas the properties of the individual components are typically well understood by most chemists, translating that chemical insight into polymer networks themselves is limited by the statistical and poorly defined nature of network structures. As a result, it is challenging, if not currently impossible, to extrapolate from the molecular behavior of components to the full range of performance and properties of the entire polymer network. Polymer networks therefore present an unrealized, important, and interdisciplinary opportunity to exert molecular-level, chemical control on material macroscopic properties. A barrier to sophisticated molecular approaches to polymer networks is that the techniques for characterizing the molecular structure of networks are often unfamiliar to many scientists. Here, we present a critical overview of the current characterization techniques available to understand the relation between the molecular properties and the resulting performance and behavior of polymer networks, in the absence of added fillers. We highlight the methods available to characterize the chemistry and molecular-level properties of individual polymer strands and junctions, the gelation process by which strands form networks, the structure of the resulting network, and the dynamics and mechanics of the final material. The purpose is not to serve as a detailed manual for conducting these measurements but rather to unify the underlying principles, point out remaining challenges, and provide a concise overview by which chemists can plan characterization strategies that suit their research objectives. Because polymer networks cannot often be sufficiently characterized with a single method, strategic combinations of multiple techniques are typically required for their molecular characterization.
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Affiliation(s)
- Scott P O Danielsen
- Marsico Lung Institute, University of North Carolina, Chapel Hill, North Carolina 27599, United States
| | - Haley K Beech
- Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Shu Wang
- Department of Chemistry, Duke University, Durham, North Carolina 27708, United States
| | - Bassil M El-Zaatari
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - Xiaodi Wang
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | | | | | - Zi Wang
- Department of Chemistry, Duke University, Durham, North Carolina 27708, United States
| | - Patricia N Johnson
- Department of Chemistry, Duke University, Durham, North Carolina 27708, United States
| | - Yixin Hu
- Department of Chemistry, Duke University, Durham, North Carolina 27708, United States
| | - David J Lundberg
- Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Georgi Stoychev
- Marsico Lung Institute, University of North Carolina, Chapel Hill, North Carolina 27599, United States
| | - Stephen L Craig
- Department of Chemistry, Duke University, Durham, North Carolina 27708, United States
| | - Jeremiah A Johnson
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Julia A Kalow
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - Bradley D Olsen
- Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Michael Rubinstein
- Marsico Lung Institute, University of North Carolina, Chapel Hill, North Carolina 27599, United States.,Department of Chemistry, Duke University, Durham, North Carolina 27708, United States.,Departments of Biomedical Engineering and Physics, Duke University, Durham, North Carolina 27708, United States.,World Primer Institute for Chemical Reaction Design and Discovery (WPI-ICReDD), Hokkaido University, Kita 21 Nishi 10, Kita-ku, Sapporo, Hokkaido 001-0021, Japan
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12
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Shannahan LS, Lin Y, Berry JF, Barbee MH, Fermen-Coker M, Craig SL. Onset of Mechanochromic Response in the High Strain Rate Uniaxial Compression of Spiropyran Embedded Silicone Elastomers. Macromol Rapid Commun 2020; 42:e2000449. [PMID: 33089596 DOI: 10.1002/marc.202000449] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2020] [Revised: 09/30/2020] [Indexed: 12/25/2022]
Abstract
The molecular processes that accompany dynamic mechanical response to large deformations at high strain rate (≈1000 s-1 or higher) underlie the early stages of damage in materials, but understanding of material response in this regime is typically limited to macroscopic constitutive equations. Here, spiropyran mechanophores are embedded in very short, stress-bearing strands in silicone elastomers, and their mechanochromic response to uniaxial compression is explored in a Split Hopkinson Pressure (or Kolsky) Bar. At strain rates of 1000 s-1 , the onset of mechanochromism occurs at lower strains, but higher stresses, than in the same materials under quasi-static loading. Similar to quasi-static loading, however, a negligible effect of mechanophore structure on the critical strain for colorimetric onset is observed. The results suggest that nonequilibrium, inhomogeneous local tension distributions in the elastomers lead to greater stress in individual strands than at the same strains under equilibrium loading, but that within the regions of force concentration, mechanochromic onset is determined primarily by a limiting local strain threshold.
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Affiliation(s)
| | - Yangju Lin
- Department of Chemistry, Duke University, 124 Science Drive, Durham, NC, 27708-0346, USA
| | - James F Berry
- US Army Research Laboratory, Maryland City, MD, 21005, USA
| | - Meredith H Barbee
- Department of Chemistry, Duke University, 124 Science Drive, Durham, NC, 27708-0346, USA
| | | | - Stephen L Craig
- Department of Chemistry, Duke University, 124 Science Drive, Durham, NC, 27708-0346, USA
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13
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Ilan Y. Order Through Disorder: The Characteristic Variability of Systems. Front Cell Dev Biol 2020; 8:186. [PMID: 32266266 PMCID: PMC7098948 DOI: 10.3389/fcell.2020.00186] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2019] [Accepted: 03/05/2020] [Indexed: 12/17/2022] Open
Abstract
Randomness characterizes many processes in nature, and therefore its importance cannot be overstated. In the present study, we investigate examples of randomness found in various fields, to underlie its fundamental processes. The fields we address include physics, chemistry, biology (biological systems from genes to whole organs), medicine, and environmental science. Through the chosen examples, we explore the seemingly paradoxical nature of life and demonstrate that randomness is preferred under specific conditions. Furthermore, under certain conditions, promoting or making use of variability-associated parameters may be necessary for improving the function of processes and systems.
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Affiliation(s)
- Yaron Ilan
- Department of Medicine, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
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14
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Lin Y, Hansen HR, Brittain WJ, Craig SL. Strain-Dependent Kinetics in the Cis-to-Trans Isomerization of Azobenzene in Bulk Elastomers. J Phys Chem B 2019; 123:8492-8498. [PMID: 31525921 DOI: 10.1021/acs.jpcb.9b07088] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The cis-to-trans isomerization of azobenzene is accelerated in a bulk PDMS elastomer under uniaxial tension. The kinetics are cleanly described by a single-exponential first-order process (k = 2.7 × 10-5 s-1) in the absence of tension but become multiexponential under constant strains of 40-90%. The complex kinetics can be reasonably modeled as a two-component process. The majority (∼92%) process is slower and occurs with a rate constant that is similar to that of the unstrained system (k = 2.3-2.7 × 10-5 s-1), whereas the rate constant of the minority (∼8%) process increases from k = 10.1 × 10-5 s-1 at 40% strain to k = 21.3 × 10-5 s-1 at 90% strain. Simple models of expected force-rate relationships suggest that the average force of tension per strand in the minority component ranges from 28 to 44 pN across strains of 40-90%.
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Affiliation(s)
- Yangju Lin
- Department of Chemistry , Duke University , Durham , North Carolina 27708 , United States
| | - Heather R Hansen
- Department of Chemistry and Biochemistry , Texas State University , San Marcos , Texas 78666 , United States
| | - William J Brittain
- Department of Chemistry and Biochemistry , Texas State University , San Marcos , Texas 78666 , United States
| | - Stephen L Craig
- Department of Chemistry , Duke University , Durham , North Carolina 27708 , United States
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15
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Lin Y, Barbee MH, Chang CC, Craig SL. Regiochemical Effects on Mechanophore Activation in Bulk Materials. J Am Chem Soc 2018; 140:15969-15975. [DOI: 10.1021/jacs.8b10376] [Citation(s) in RCA: 71] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Yangju Lin
- Department of Chemistry, Duke University, Durham, North Carolina 27708, United States
| | - Meredith H. Barbee
- Department of Chemistry, Duke University, Durham, North Carolina 27708, United States
| | - Chia-Chih Chang
- 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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Kulik HJ. MODELING MECHANOCHEMISTRY FROM FIRST PRINCIPLES. REVIEWS IN COMPUTATIONAL CHEMISTRY 2018. [DOI: 10.1002/9781119518068.ch6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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17
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Barbee MH, Kouznetsova T, Barrett SL, Gossweiler GR, Lin Y, Rastogi SK, Brittain WJ, Craig SL. Substituent Effects and Mechanism in a Mechanochemical Reaction. J Am Chem Soc 2018; 140:12746-12750. [PMID: 30260221 DOI: 10.1021/jacs.8b09263] [Citation(s) in RCA: 67] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We report the effect of substituents on the force-induced reactivity of a spiropyran mechanophore. Using single molecule force spectroscopy, force-rate behavior was determined for a series of spiropyran derivatives substituted with H, Br, or NO2 para to the breaking spirocyclic C-O bond. The force required to achieve the rate constants of ∼10 s-1 necessary to observe transitions in the force spectroscopy experiments depends on the substituent, with the more electron withdrawing substituent requiring less force. Rate constants at 375 pN were determined for all three derivatives, and the force-coupled rate dependence on substituent identity is well explained by a Hammett linear free energy relationship with a value of ρ = 2.9, consistent with a highly polar transition state with heterolytic, dissociative character. The methodology paves the way for further application of linear free energy relationships and physical organic methodologies to mechanochemical reactions, and the characterization of new force probes should enable additional, quantitative studies of force-coupled molecular behavior in polymeric materials.
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Affiliation(s)
- Meredith H Barbee
- Department of Chemistry , Duke University , Durham , North Carolina 27708 , United States
| | - Tatiana Kouznetsova
- Department of Chemistry , Duke University , Durham , North Carolina 27708 , United States
| | - Scott L Barrett
- Department of Chemistry and Biochemistry , Texas State University , San Marcos , Texas 78666 , United States
| | - Gregory R Gossweiler
- Department of Chemistry , Duke University , Durham , North Carolina 27708 , United States
| | - Yangju Lin
- Department of Chemistry , Duke University , Durham , North Carolina 27708 , United States
| | - Shiva K Rastogi
- Department of Chemistry and Biochemistry , Texas State University , San Marcos , Texas 78666 , United States
| | - William J Brittain
- Department of Chemistry and Biochemistry , Texas State University , San Marcos , Texas 78666 , United States
| | - Stephen L Craig
- Department of Chemistry , Duke University , Durham , North Carolina 27708 , United States
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Sammon MS, Ončák M, Beyer MK. Theoretical simulation of the infrared signature of mechanically stressed polymer solids. Beilstein J Org Chem 2017; 13:1710-1716. [PMID: 28904614 PMCID: PMC5564256 DOI: 10.3762/bjoc.13.165] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2017] [Accepted: 07/26/2017] [Indexed: 11/23/2022] Open
Abstract
Mechanical stress leads to deformation of strands in polymer solids, including elongation of covalent bonds and widening of bond angles, which changes the infrared spectrum. Here, the infrared spectrum of solid polymer samples exposed to mechanical stress is simulated by density functional theory calculations. Mechanical stress is described with the external force explicitly included (EFEI) method. The uneven distribution of the external stress on individual polymer strands is accounted for by a convolution of simulated spectra with a realistic force distribution. N-Propylpropanamide and propyl propanoate are chosen as model molecules for polyamide and polyester, respectively. The effect of a specific force on the polymer backbone is a redshift of vibrational modes involving the C-N and C-O bonds in the backbone, while the free C-O stretching mode perpendicular to the backbone is largely unaffected. The convolution with a realistic force distribution shows that the dominant effect on the strongest infrared bands is not a shift of the peak position, but rather peak broadening and a characteristic change in the relative intensities of the strongest bands, which may serve for the identification and quantification of mechanical stress in polymer solids.
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Affiliation(s)
- Matthew S Sammon
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
| | - Milan Ončák
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
| | - Martin K Beyer
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
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