Strain glass analogue in a bent-core liquid crystal exhibiting the dark conglomerate phase

Abstract

Vitrified states formed from the dark conglomerate liquid crystal (DCLC) phase, by two members of a homologous series made of bent-core molecules derived from 2,7-dihydroxynaphthalene under different cooling procedures, have been characterised using a variety of experimental techniques, such as optical microscopy, differential scanning calorimetry, X-ray diffraction, electro-optics, dielectric spectroscopy and atomic force microscopy. The experimental results show that though the vitrified state formed on gradual cooling of the sample from the DC phase has some glassy features, it is fragile and undergoes crystallisation over time. On the other hand, direct quenching of the DC phase to room temperature results in stronger glass formation. We propose that the vitrified state obtained on progressive cooling of the DC phase may have some analogy to strain glass and that the DC phase itself may be rather like unfrozen strain glass.