Mechanochromic Luminescent Materials

Many TPE derivatives and TAEs have been found to possess the mechanochromic luminescent property [33]. For example, compound 38 is a simple-structured 

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Abstract We describe mechanochromic and thermochromic photoluminescent liquid crystals. In particular, mechanochromic photoluminescent liquid crystals found recently, which are new stimuli-responsive materials are reported. For example, photoluminescent liquid crystals having bulky dendritic moieties with long alkyl chains change their photoluminescent colors by mechanical stimuli associated with isothermal phase transitions. The photoluminescent properties of molecular assemblies depend on their assembled structures. Therefore, controlling the structures of molecular assemblies with external stimuli leads to the development of stimuli-responsive luminescent materials. Mechanochromic photoluminescent properties are also observed for a photoluminescent metallomesogen and a liquid-crystalline polymer. We also show thermochromic photoluminescent liquid crystals based on origo-(/ -phenylenevinylene) and anthracene moieties and a thermochromic photoluminescent metallocomplex. 

Many other piezochromic or mechanochromic organic materials are now known, some of which (23, 24, 25 and 26 ) are shown in Scheme 7. It is worth noting that the mode of applied stress can be distinguished by the different luminescent response. The yellow luminescence (2em = 556 nm) of a tetrathiazolylthiophene (27) crystal is blue-shifted to green (Agm = 490 nm) by anisotropic grinding but is red-shifted to orange (Agm = 609nm at 3.2 GPa) under isotropic compression, which is explained by decreased and increased contributions of excimer emission, respectively. 

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