Blue-Shifting Mechanofluorochromic Luminescent Behavior of Polymer Composite Films Using Gelable Mechanoresponsive Compound

Abstract

Mechanochromic luminescent dyes change their luminescence color upon exposure to external mechanical stimuli. In this study, we synthesized a liquid crystalline mechanochromic luminescent dye containing a terminal cholesterol molecule. The dissolution of the dye in 1,4-dioxane resulted in the formation of a gel. The luminescence of the xerogel obtained from the dioxane solution changed from green to blue upon grinding, indicating mechanochromic luminescence behavior. The anisotropic patterning of short-wavelength-shifted luminescence color change by directional handwriting on surface layer of liquid crystal was successfully demonstrated. Furthermore, blue-shifting mechanoresponsive polymer composite surface was fabricated by using the luminophore.

Multichromic Behavior of Liquid Crystalline Composite Polymeric Films

“…The color did not change when the cathode and anode were switched. Compared to the data reported in a previous paper [18], the maximum absorption wavelength is shorter than that of non-quaternized oligothiophene. Therefore, the luminophores may have been decomposed, as well as cleavage of the π-conjugated structure by the reduction potential, resulting in an irreversible electrical response.…”

“…These electronic structures were similar to those of the protonated cyanostyrobazole derivatives; cholesterol was predicted to be present in a bent conformation at right angles from the conjugated moiety. This is because, in the previous structure, cholesterol was linked to the quaternized cyanostyrobazole via a bromoacetate ester, whereas in the present structure, cholesterol was linked as a benzoate ester, and the linearity was reduced [18].…”

“…The formation of molecular pairs leads to the formation of bifunctional cholesterol at the ends of the complexes, which are expected to form gels when linked one-dimensionally via intermolecular interactions [4,17]. In addition, we reported that the spin-coated film formed from the sol state exhibits a friability response, and that, by utilizing its liquid crystalline nature, it exhibits polarized luminescence when oriented parallel to the friability direction, enabling the recognition of the friability direction [18].…”