Molecular Damage Detection in an Elastomer Nanocomposite with a Coumarin Dimer Mechanophore. Issue 1 (6th August 2020)

• Record Type: Journal Article
• Authors: Zhang, Yudi; Lund, Ethen; Gossweiler, Gregory R.; Lee, Bobin; Niu, Zhenbin; Khripin, Constantine; Munch, Etienne; Couty, Marc; Craig, Stephen L.
• Other Names: Chen Yulan guestEditor.; Sommer Michael guestEditor.; Weder Christoph guestEditor.
• Is Part Of: Macromolecular rapid communications. Volume 42:Issue 1(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-08-06
• Subjects: coumarin -- mechanochromism -- nanocomposite -- sonication; Macromolecules -- Periodicals; Polymers -- Periodicals; Chemistry -- Periodicals; 547.705
• DOI: 10.1002/marc.202000359
• Languages: English
• ISSNs: 1022-1336

Abstract

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. Abstract : A coumarin dimer probe has comparable mechanical strength to disulfides and functions as a detectable, selective site of scission within the matrix of particle‐filled butadiene co‐polymer cylinders compressed uniaxially. A second probe is shown to have even greater turn‐on response when incorporated at the interface between filler particles and matrix.