Crystallization-induced mechanofluorescence for visualization of polymer crystallization

Abstract

The growth of lamellar crystals has been studied in particular for spherulites in polymeric materials. Even though such spherulitic structures and their growth are of crucial importance for the mechanical and optical properties of the resulting polymeric materials, several issues regarding the residual stress remain unresolved in the wider context of crystal growth. To gain further insight into micro-mechanical forces during the crystallization process of lamellar crystals in polymeric materials, herein, we introduce tetraarylsuccinonitrile (TASN), which generates relatively stable radicals with yellow fluorescence upon homolytic cleavage at the central C–C bond in response to mechanical stress, into crystalline polymers. The obtained crystalline polymers with TASN at the center of the polymer chain allow not only to visualize the stress arising from micro-mechanical forces during polymer crystallization via fluorescence microscopy but also to evaluate the micro-mechanical forces upon growing polymer lamellar crystals by electron paramagnetic resonance, which is able to detect the radicals generated during polymer crystallization.

Bowls, vases and goblets—the microcrockery of polymer and nanocomposite morphology revealed by two-photon optical tomography

“…In materials science it has been utilized in studies of polymer blends and block copolymers 29 – 31 , relying on the difference in solubility or binding of the dye in the chemically different domains. We are aware of only one, indeed a very interesting recent use of this technique in a thin-film homopolymer, where a mechanically cleavable group was incorporated into the chains to give fluorescent radicals, thus marking stress points in the crystallizing material 32 . To observe true 3D morphology in bulk homopolymers here we create contrast in two different ways: (a) by first producing a uniform blend of polymer and fluorophore and then allowing partial exclusion of the fluorophore from the growing spherulites, which results in the dye being concentrated at spherulite boundaries; (b) by immersing the already crystallized polymer in a solution of a fluorescent dye and relying on the dye’s preferential diffusion and deposition along spherulite boundaries.…”

Mechanochemiluminescent Hydrogels for Real-Time Visualization of Chemical Bond Scission

“…reactions with spectroscopic signals are advanced in illuminating the fracture mechanics of tough soft materials with high resolution. Typical mechanophores and the corresponding visualized outputs include mechanically induced color change (such as spiropyran, 13 diarylbibenzofuranone, 14 and more), induction or fading of fluorescence (such as rhodamine, 15 anthracene dimers 16 ), and mechanochemiluminescence (bis(adamantyl)-1,2-dioxetane, Ad 17 ).…”

Molecular copper iodide clusters: a distinguishing family of mechanochromic luminescent compounds

“…[1][2][3][4][5][6][7] Regarding their potential applications, one of the most attractive feature of these stimuli-responsive materials is the straightforward detection of the emission changes by simple non-invasive spectroscopic means or even with the naked eye. [8][9][10][11] Even though the number of reported compounds exhibiting luminescence mechanochromism has greatly increased over the past decade, in-depth studies analysing the underlying mechanisms remain relatively rare. However, such studies are of crucial importance not only from a fundamental point of view but also to guide further development of these stimuliresponsive materials with optimized properties.…”