Covalent Mechanochemistry and Contemporary Polymer Network Chemistry: A Marriage in the Making

Lloyd, Evan M.; Vakil, Jafer R.; Yao, Yunxin; Sottos, Nancy R.; Craig, Stephen L.

doi:10.1021/jacs.2c09623

Cited by 68 publications

(48 citation statements)

References 177 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This result is not surprising as the discrepancy between predicted and observed mechanochemical reactivity has already been reported in the literature 44,50 and unravelling the molecular features that dictate (the extent of) mechanophores' activation in polymer materials is one of the open challenges in the field. 51 Moreover, the participation of HEA in the mechanochemical process as observed with the ethanol molecule in the CoGEF calculations of Tr-C (vide supra) cannot be excluded in the present system.…”

Section: ■ Results and Discussionmentioning

confidence: 80%

Triarylmethane Mechanophores Enable Full-Visible Spectrum Mechanochromism

Hemmer,

Bauernfeind,

Rader

et al. 2023

Macromolecules

View full text Add to dashboard Cite

Covalent mechanophores are molecular motifs that contain weak bonds, which are preferentially cleaved in response to the application of a mechanical force. Specially designed motifs can signal such bond scission events by changing their optical absorption or emission characteristics and thus exhibit mechanochromism. Here, we report the synthesis of three triarylmethane benzyl ether derivatives and their use as mechanochromic cross-linkers in elastomeric networks. Mechanical stimulation of these polymers triggers the heterolytic cleavage of the C–O ether bond of the triarylmethanes, which leads to the formation of resonance-stabilized carbocations that absorb light in the visible range. The materials adopt blue, yellow, or red coloration depending on the chemical design of the triarylmethane mechanophore. The color palette can be further expanded by simple combinations of these three colors. Thus, our work demonstrates the versatility of the triarylmethane platform in polymer mechanochemistry.

show abstract

Section: ■ Results and Discussionmentioning

confidence: 80%

Triarylmethane Mechanophores Enable Full-Visible Spectrum Mechanochromism

Hemmer,

Bauernfeind,

Rader

et al. 2023

Macromolecules

View full text Add to dashboard Cite

show abstract

“…A wide range of mechanophores have been developed, enabling polymeric materials to exhibit a useful and diverse set of responses to applied force. Mechanophores that change color in response to force, for example, provide an efficient way of monitoring the molecular-scale forces experienced by a material and have practical applications in damage reporting and stress- or strain-sensing materials. − Mechanophores with other chemical responses to force similarly have uses in self-healing materials, synthetic chemistry, and drug delivery, to name only a few applications. ,− A significant challenge in the development of efficient mechanochemical materials, however, is that only a limited fraction of the mechanophores are typically activated when the material is deformed. − Thus, it is critical to understand, from a fundamental perspective, what features of polymer networks determine the mechanochemical responses of the materials and how network structure can be tuned to optimize this response.…”

Section: Introductionmentioning

confidence: 99%

Effect of Polymer Composition and Morphology on Mechanochemical Activation in Nanostructured Triblock Copolymers

et al. 2023

View full text Add to dashboard Cite

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.

show abstract

“…Polymer networks should be a useful platform for driving mechanochemical activation on large numbers of molecules at once. However, yields of force-driven reactions in elastomeric polymer networks are typically low, even for mechanophores that exhibit high activation yields in solution sonication experiments. , Structural and topological heterogeneity have recently been identified as key factors that may reduce the efficiency of force transmission from the macroscopic to the molecular scale . In particular, spatial heterogeneity in the distribution of cross-links, defects, and dispersity in the network strand lengths may all contribute to broad molecular-scale force distributions that lead to activation of mechanophores in only the small number of strands experiencing the highest force .…”

mentioning

confidence: 99%

Preferential Mechanochemical Activation of Short Chains in Bidisperse Triblock Elastomers

Huo,

Watkins,

Jeong

et al. 2023

ACS Macro Lett.

View full text Add to dashboard Cite

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 microphasesegregated polymers is a promising design strategy for efficient mechanochemical activation in bulk materials.

show abstract

Covalent Mechanochemistry and Contemporary Polymer Network Chemistry: A Marriage in the Making

Cited by 68 publications

References 177 publications

Triarylmethane Mechanophores Enable Full-Visible Spectrum Mechanochromism

Triarylmethane Mechanophores Enable Full-Visible Spectrum Mechanochromism

Effect of Polymer Composition and Morphology on Mechanochemical Activation in Nanostructured Triblock Copolymers

Preferential Mechanochemical Activation of Short Chains in Bidisperse Triblock Elastomers

Contact Info

Product

Resources

About