Stress-sensing thermoset polymer networks via grafted cinnamoyl/cyclobutane mechanophore units in epoxy

Nofen, Elizabeth; Zimmer, Nicholas; Dasgupta, Avi; Gunckel, Ryan; Koo, Bonsung; Chattopadhyay, Aditi; Dai, Lenore L.

doi:10.1039/c6py01463a

Cited by 20 publications

(23 citation statements)

References 52 publications

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“…Polymer Chemistry materials science applications. 1,[52][53][54][55][56][57][58][59] For example, a cinnamate dimer was successfully embedded in a thermoset polymer and restored its π-conjugation upon cycloreversion hence giving rise to a fluorescence-based damage reporting nanocomposite network. 52 A similar approach was developed to design a nonscissile mechanophore exhibiting mechanochromism.…”

Section: Reviewmentioning

confidence: 99%

“…1,[52][53][54][55][56][57][58][59] For example, a cinnamate dimer was successfully embedded in a thermoset polymer and restored its π-conjugation upon cycloreversion hence giving rise to a fluorescence-based damage reporting nanocomposite network. 52 A similar approach was developed to design a nonscissile mechanophore exhibiting mechanochromism. For this, a bicyclic structure was devised also increasing the rate of the forward [2 + 2] cycloaddition, and thus healing after crack formation, considerably due to the increased local concentrations of the reactants (Scheme 11).…”

Section: Reviewmentioning

confidence: 99%

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Polymer mechanochemistry-enabled pericyclic reactions

et al. 2020

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Section: Reviewmentioning

confidence: 99%

Section: Reviewmentioning

confidence: 99%

Polymer mechanochemistry-enabled pericyclic reactions

et al. 2020

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“…[ 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 a). [ 12,28 ] But, to the best of our knowledge, mechanochromophores have yet to be employed as detection agents in analogues of particle‐reinforced hydrocarbon elastomers such as polybutadiene.…”

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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“…Nevertheless, recently some mechanochromic systems have been specifically developed for epoxy resins and other thermosets that are commonly used as matrices for reinforced composites. Dai's group substituted part of the amine hardener of an epoxy formulation with cinnamamide, the amide of cinnamic acid, which undergoes UV‐induced [2 + 2] cycloaddition to its cyclobutane‐containing dimer . In addition, dimers of cinnamamide were directly reacted with an excess of the epoxy monomer, followed by addition of the hardener.…”

Section: Mechanochromic Fiber‐reinforced Compositesmentioning

confidence: 99%

Self‐Reporting Fiber‐Reinforced Composites That Mimic the Ability of Biological Materials to Sense and Report Damage

et al. 2018

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Sensing of damage, deformation, and mechanical forces is of vital importance in many applications of fiber-reinforced polymer composites, as it allows the structural health and integrity of composite components to be monitored and microdamage to be detected before it leads to catastrophic material failure. Bioinspired and biomimetic approaches to self-sensing and self-reporting materials are reviewed. Examples include bruising coatings and bleeding composites based on dye-filled microcapsules, hollow fibers, and vascular networks. Force-induced changes in color, fluorescence, or luminescence are achieved by mechanochromic epoxy resins, or by mechanophores and force-responsive proteins located at the interface of glass/carbon fibers and polymers. Composites can also feel strain, stress, and damage through embedded optical and electrical sensors, such as fiber Bragg grating sensors, or by resistance measurements of dispersed carbon fibers and carbon nanotubes. Bioinspired composites with the ability to show autonomously if and where they have been damaged lead to a multitude of opportunities for aerospace, automotive, civil engineering, and wind-turbine applications. They range from safety features for the detection of barely visible impact damage, to the real-time monitoring of deformation of load-bearing components.

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Stress-sensing thermoset polymer networks via grafted cinnamoyl/cyclobutane mechanophore units in epoxy

Abstract: A study of novel direct covalent grafting of photoactive mechanophore units into an epoxy matrix to create self-sensing thermoset network nanocomposites.

Cited by 20 publications

References 52 publications

Polymer mechanochemistry-enabled pericyclic reactions

Polymer mechanochemistry-enabled pericyclic reactions

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

Self‐Reporting Fiber‐Reinforced Composites That Mimic the Ability of Biological Materials to Sense and Report Damage

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