Molecular Crystals and Liquid Crystals, Vol.594, No.1, 112-121, 2014
Mechanochromic Photoluminescent Liquid Crystals Containing 5,5'-Bis(2-phenylethynyl)-2,2'-bithiophene
5,5 '-Bis(2-phenylethynyl)-2,2 '-bithiophene derivative 1 containing dendritic moieties linked through amide groups was synthesized. Compound 1 exhibits a rectangular columnar phase on slow cooling from the isotropic liquid. In contrast, a cubic phase is formed as a metastable liquid-crystalline phase by rapid cooling of the isotropic melt. Mechanical shearing induces a cubic-columnar phase transition, accompanied by the change of a photoluminescent color from yellow-green to green. The infrared spectra of 1 suggest that the mechanical stimuli can induce the partial dissociation of the hydrogen bond. This may lead to more disordering of the pi-stacks of chromophores.