As researchers heated this sample of a liquid crystal called PCH past 70 °C, the molecules changed from a liquid crystalline phase, in which they assembled into a series of ordered helices, to a so-called isotropic liquid phase that has little molecular order. The twist in each helix is imparted by a small amount of the chiral molecule pregnenolone. As the helices effectively melted and unraveled in the increasingly high temperatures, the liquid changed its shape and appearance as seen here. Vance Williams’s group at Simon Fraser University used optical microscopy (at 10× magnification) and cross-polarized light conditions to study this sample of chiral liquid crystals, which can be used in thermometers and even mood rings. Because the pregnenolone molecules are chiral and enantiomerically pure, cross-polarized light creates a range of colors when it shines through the sample.
Credit: Vance Williams
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