Anthracene-based mechanophores for compression-activated fluorescence in polymeric networks

Kabb, Christopher P.; O'Bryan, Christopher S.; Morley, Cameron; Angelini, Thomas E.; Sumerlin, Brent S.

doi:10.1039/c9sc02487e

Cited by 63 publications

(66 citation statements)

References 46 publications

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“…Further, the experimental procedure developed here provides a methodology to quantify and compare mechanophore activation in a complex system with excellent sensitivity, unveiling a more quantitative picture of how mechanical stress is transferred at the molecular scale in highly entangled cross‐linked polymer nanocomposite under compressive loading. These strategies are potentially applicable in other elastomer‐based composite systems and mechanophores that generate fluorescence signals after activation irreversibly such as anthracene‐based, [ 16,48,49 ] cinnamate dimer based, [ 50,51 ] and rhodamine‐based [ 52,53 ] molecules reported previously. The foundation developed by this work could enable the development of mechanoresponsive composites that not only qualitatively report mechanical damage but quantify the extent of damage and repair autonomously as well.…”

Section: Figurementioning

confidence: 99%

Molecular Damage Detection in an Elastomer Nanocomposite with a Coumarin Dimer Mechanophore

Zhang

Lund

Gossweiler

et al. 2020

Macromol. Rapid Commun.

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resistance that result from dispersing stiffer particulates or fibers into the softer polymer matrix. [2,3] In high performance polymer composites, mechanical performance is often determined by how stress transfer from the matrix to the filler either prevents or facilitates the formation of voids, depending on the mechanism of toughening. [4,5] Stress overload can lead to the scission of covalent bonds or chain slippage and induce irreversible structural changes at the molecular, mesoscopic, and macroscopic levels, [6-8] ultimately leading to catastrophic material failure. Therefore, damage detection in polymer composites has long been an active area of study from both fundamental and applied perspectives. Currently, damage detection in composites is mostly achieved through techniques such as ultrasonics, computerized vibro-thermography, x-ray tomography and infrared thermography. [9] These techniques are non-destructive, and in some cases they have been applied in combination with methods for repairing the damage, such as resin injection and the use of reinforcing patches. [9] In addition, higher resolution techniques such as scanning electron microscopy and transmission electron microscopy have been used in post-mortem damage analysis in composites. [10,11] These methods have been quite successful, but they require that material damage has progressed to the point of nanoscale to mesoscale defects in order to be detected, and they do not directly probe the nature of the specific molecular events that are responsible for damage initiation and/or propagation. Polymer mechanochemistry offers exciting opportunities for stress-sensing and damage detection in polymer composites through incorporating mechanophores, which are molecular units that react in response to force. [12,13] By embedding different mechanophores, materials can be endowed with stress-responsive properties that include changes in modulus, [14,15] color, [16-19] and electronic properties. [20] Recent years have seen increased efforts to utilize mechanophores in bulk composites, [21-27] and mechanophores that provide irreversible optical responses to mechanical events are promising candidates to characterize the molecular stresses caused by wear or fatigue (Figure 1a). [12,28] But, to the best of our knowledge, mechanochromophores have 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 mol...

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Section: Figurementioning

confidence: 99%

Molecular Damage Detection in an Elastomer Nanocomposite with a Coumarin Dimer Mechanophore

Zhang

Lund

Gossweiler

et al. 2020

Macromol. Rapid Commun.

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“…In the future we plan to apply our methodology to a recently proposed mechanophore based on anthracene, [54] for which flex‐activation was tested but remained unsuccessful, with the aim of determining the optimal conditions (e. g. the pulling/deformation setup) for successful flex‐activation. Moreover, we plan to apply quantum mechanochemical models of pressure [55–58] to test the efficiency of flex‐activation in polymers, since experiments on flex‐activated mechanophores were performed under compression [24–26] .…”

Section: Methodsmentioning

confidence: 99%

The Mechanism of Flex‐Activation in Mechanophores Revealed By Quantum Chemistry

et al. 2020

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Flex‐activated mechanophores can be used for small‐molecule release in polymers under tension by rupture of covalent bonds that are orthogonal to the polymer main chain. Using static and dynamic quantum chemical methods, we here juxtapose three different mechanical deformation modes in flex‐activated mechanophores (end‐to‐end stretching, direct pulling of the scissile bonds, bond angle bendings) with the aim of proposing ways to optimize the efficiency of flex‐activation in experiments. It is found that end‐to‐end stretching, which is a traditional approach to activate mechanophores in polymers, does not trigger flex‐activation, whereas direct pulling of the scissile bonds or displacement of adjacent bond angles are efficient methods to achieve this goal. Based on the structural, energetic and electronic effects responsible for these observations, we propose ways of weakening the scissile bonds experimentally to increase the efficiency of flex‐activation.

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“…As indicated above, mechano‐responsive self‐reporting materials (also known as self‐sensing or self‐monitoring) [23] are considered the most prevailing ones based on the multitude of studies and possible applications (e.g. load bearing, high performance, aerospace, automobiles, biotechnology) [23–28] . Mechanical forces apply to all different types of such materials, thus it is of critical importance to detect damages as early as possible to prevent catastrophic failures.…”

Section: Stimuli‐responsive Self‐reporting Polymeric Materialsmentioning

confidence: 99%

Prevent or Cure—The Unprecedented Need for Self‐Reporting Materials

2021

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Hatice Mutlu, born in Bulgaria, studied Chemistry at Marmara University and Bogazici University.S ubsequently, she obtained her PhD from the Karlsruhe Institute of Technology (KIT) in the group of M. A. R. Meier.After post-doctoral stays in the groups of J.-F. Lutz (ICS-CNRS, Strasbourg) and C. Barner-Kowollik (KIT), she currently works as asenior researcher at KIT.Her research interest spans from the synthesis of complex macromolecular architecturesand functional polymers to the development of new polymer-forming reactions and novel conjugation chemistries with aparticularfocus on the design of novel sulfur-based and self-reporting materials. Christopher Barner-Kowollik, Australian Research Council (ARC) Laureate Fellow, graduated in chemistry from Gçttingen University,G ermany,and joined the University of New South Wales in early 2000 rising to lead the Centre for Advanced Macromolecular Design in 2006 as one of its directors. He returned to Germany to the KIT in 2008, where he establishedand led aDFG-funded Centre of Excellence in soft matter synthesis. He moved to QUT in 2017 and established QUT'sSoft Matter Materials Laboratory. His research achievements have been recognized by an array of national and international awards.

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Anthracene-based mechanophores for compression-activated fluorescence in polymeric networks

Abstract: The recent attention given to functionalities that respond to mechanical force has led to a deeper understanding of force transduction and mechanical wear in polymeric materials.

Cited by 63 publications

References 46 publications

Molecular Damage Detection in an Elastomer Nanocomposite with a Coumarin Dimer Mechanophore

Molecular Damage Detection in an Elastomer Nanocomposite with a Coumarin Dimer Mechanophore

The Mechanism of Flex‐Activation in Mechanophores Revealed By Quantum Chemistry

Prevent or Cure—The Unprecedented Need for Self‐Reporting Materials

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