Dye-containing polymers: methods for preparation of mechanochromic materials

Abstract

The detection of mechanical stress in polymeric materials through optical variations has attracted considerable interest over the past ten years. In this tutorial review, the current state of knowledge concerning the preparation of polymers with mechanochromic features is summarized. Two types of procedures are illustrated and thoroughly discussed along with their respective structure-property relationships: the first resides in the physical dispersion of the dye in the form of supramolecular aggregates in a preformed polymer matrix; the second involves the covalent insertion of chromophoric units into the macromolecule backbone or side chains. Herein we review the simplicity of the preparative routes available, and their influence over the properties of the resulting dye-polymer systems, by focussing on the most illustrative examples described in the literature. Special reference is made to stimuli-responsiveness as a mechanical means towards innovative smart and intelligent materials.

Absorption and Emission Spectra of a Flexible Dye in Solution: A Computational Time-Dependent Approach

“…Organic dyes 1 have recently attracted a growing attention, thanks to their wide range of applications, that covers different fields in both materials [2][3][4][5][6][7][8][9][10][11] and life sciences. [12][13][14][15] In particular, the high selectivity and specificity of some fluorescent molecules in detecting particular molecular targets and/or in modulating the responses to different external stimuli are often exploited to investigate the structural and dynamic properties of a wide variety of complex systems like, e.g., polymeric materials, DNA structures, protein conformations or lipid aggregates.…”

“…the polymer and the dye) can be tuned by mechanical stress, in order to properly control both the absorption and emission responses. 8,9,11 Spectroscopic techniques are becoming the methods of choice for deeper investigations of the photophysical properties of composite materials. [16][17][18] Unfortunately, often experimental measures alone are not sufficient to unravel the subtle interplay of several effects in determining the overall result.…”

Structural, dynamic and photophysical properties of a fluorescent dye incorporated in an amorphous hydrophobic polymer bundle

“…Complementary information about dye spinning and tumbling are also retrieved by calculating the reorientation of the abovementioned axes. Indeed, re-orientational times are expressed as (10) where and are the first and second rank Legendre polynomial of the function…”

“…The incorporation of photo-responsive chromophores into polymer matrices enables the creation of receptive compounds, sometimes referred to as "smart" polymers, [6][7][8][9][10][11] which could change their optical or electronic characteristics upon light irradiation. The integrated molecules could be dispersed inside the polymer matrices 12 or covalently bound to the chains of the polymers, 13,14 thus determining specific responses, such as changes in size, shape and polarity, 15 of the composite materials to the external stimuli.…”

Mechanochemistry in Polymers with Supramolecular Mechanophores

“…[27] Thus, it is possible to influence the photophysical properties of polymer-based materials by altering the aggregation state of embedded π-conjugated chromophores through the application of mechanical forces. [28][29][30][31] One of the first attempts to strategically use the mechanically induced disassembly of aggregated chromophores in a polymer matrix involved a family of fluorescent dyes which form (static) excimers in their aggregated states. [32] Such complexes between two identical photoluminescent (PL) molecules, one in an electronically excited and one in its ground state, were discovered by Förster and Kasper sixty years ago.…”