Interfacial Mechanophore Activation Using Laser-Induced Stress Waves

Abstract

A new methodology is developed to activate and characterize mechanochemical transformations at a solid interface. Maleimide-anthracene mechanophores covalently anchored at a fused silica-polymer interface are activated using laser-induced stress waves. Spallation-induced mechanophore activation is observed above a threshold activation stress of 149 MPa. The retro [4+2] cycloaddition reaction is confirmed by fluorescence microscopy, XPS, and ToF-SIMS measurements. Control experiments with specimens in which the mechanophore is not covalently attached to the polymer layer exhibit no activation. In contrast to activation in solution or bulk polymers, whereby a proportional increase in mechanophore activity is observed with applied stress, interfacial activation occurs collectively with spallation of the polymer film.

Spatially Selective and Density-Controlled Activation of Interfacial Mechanophores

“…Active specimens with Maleimide-Anthracene (MA) mechanophores immobilized on the surface were prepared with a surface functionalization approach following previously reported methods, shown in Figure S4. 3 In this work, the surface-bound MA mechanophores terminated with a bromoisobutyrate group were used to initiate a copper-catalyzed living radical polymerization of glycidyl methacrylate to grow polymer brushes.…”

Rotaxane-Based Mechanophores Enable Polymers with Mechanically Switchable White Photoluminescence

“…1−3 Mechanochromic (luminescent) polymers can signal mechanical stresses and visualize material damage ahead of structural failure. 4−23 Conventional mechanophores that are activated by the mechanically induced scission of covalent bonds suffer from several limitations, which are directly related to their general operating mechanism. First, the activation requires a relatively high activation energy, as the process involves the cleavage of covalent chemical bonds that are supposed to be stable in the absence of mechanical force.…”

Mechanoresponsive Behavior of a Polymer-Embedded Red-Light Emitting Rotaxane Mechanophore

“…4 In the meantime, many color-changing mechanophores and corresponding motifs which change their photoluminescence properties have been investigated. [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] While the latter require auxiliary means for detection, a change of the emission color and/or intensity can often be detected more easily than an absorption color change. 22 Most of the fluorescent mechanophores reported so far, emit in the blue and green wavelength region.…”

“…22 Most of the fluorescent mechanophores reported so far, emit in the blue and green wavelength region. For instance, nonemissive anthracene-maleimide Diels-Alder adducts exhibit blue emission after activation [5][6][7][8] and a bathochromic shift of the emission band can be achieved by extension of π-conjugation of the anthracene moiety. 9 1,2-Dioxetane, which is a chemiluminescent mechanophore, exhibits blue emission upon activation.…”