Rotaxane-Based Mechanophores Enable Polymers with Mechanically Switchable White Photoluminescence

Abstract

Three mechanoresponsive polyurethane elastomers whose blue, green, and orange photoluminescence can be reversibly turned on by mechanical force were prepared and combined to create a blend that exhibits deformation-induced white photoluminescence. The three polyurethanes contain rotaxane-based supramolecular mechanoluminophores based on π-extended pyrene, anthracene, or 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4 H -pyran (DCM) luminophores, respectively, and 1,4,5,8-naphthalenetetracarboxylic diimide as an electronically matched quencher. Each polymer shows instantly reversible, strain-dependent switching of its photoluminescence intensity when stretched and relaxed, as deformation leads to a spatial separation of the luminophore and quencher. The present study shows that the photoluminescence color can easily be tailored by variation of the luminophore and also by combining several mechanophores in one material and demonstrates that adaptability is a key advantage of supramolecular approaches to create mechanoresponsive polymers.

Mechanochromic Luminescence from Crystals Consisting of Intermolecular Hydrogen‐Bonded Sheets

“…Vibrionic structure was observed in the emission spectrum of 1 in DMF with two peaks at 482 and 511 nm and a shoulder at 550 nm (Figure b). These spectral features are typical for 9,10‐bis(phenylethynyl)anthracene derivatives . Therefore, compound 1 molecularly disperses in DMF solution.…”

“…These spectral features are typical for 9,10-bis(phenylethynyl)anthracene derivatives. [14,26,[62][63][64][65] Therefore, compound 1 molecularly dispersesi nD MF solution. The photoluminescent quantum efficiency( PLQY) of the DMF solution was 0.96.…”

Pyrene Functionalized Mechanochromic Elastomer with Switchable White Fluorescence

“…The UV-polymerizations were initiated by 2-hydroxyethyl-2-methylpropiophenone (HMP) under a UV lamp (UV-340, 100 W) with wavelength ranging from 295 to 365 nm. 1 H NMR spectra were recorded on 600 MHz (Bruker ARX300) and 13 C NMR spectra were recorded on Bruker 100 MHz spectrometer at room temperature with CDCl 3 as the solvents and tetramethylsilane (TMS) as the internal standard. Differential scanning calorimetry (DSC) measurements were carried out on TA Instruments DSC Q2000.…”

Multi‐Color Photoluminescence Based on Mechanically and Thermally Induced Liquid‐Crystalline Phase Transitions of a Hydrogen‐Bonded Benzodithiophene Derivative

“…However, the mechanoresponsive liquid crystals showing reversible high contrast mechanofluorochromism and multi‐color emissions from a single fluorophore without additives have not been reported. In addition, quantitative evaluation of the stress inducing the chromism remains a key challenge, although the tensile test has been carried out for mechanochromic polymers . The present study fills that void by providing a hexacatenar π‐conjugated LC molecule capable of forming distinct metastable mesophases.…”