Preparation of Cholesteryl Ester Liquid Crystals

Procedure based on G. H. Brown and J. J. Wolken, Liquid Crystals and Biological Systems, Academic Press, NY, 1979, pp. 165-167 and W. Elser and R. D. Ennulat, Adv. Liq. Cryst. 2, 73 (1976).

These cholesteric-nematic liquid crystals reversibly change color as the temperature changes. One of the principal advantages of liquid crystals is their ability to map out thermal regions of different temperature. Cholesteric liquid crystals can degrade when exposed to moisture or air, but as long as they are stored in a sealed container the mixture can be prepared months in advance.

Procedure

Wear eye protection

Place 0.65 g cholesteryl oleyl carbonate, 0.25 g cholesteryl pelargonate, and 0.10 g cholesteryl benzoate in a vial.

Melt the solid in a sample vial using a hair drier or heat gun.

While the mixture is still liquid, divide into several vials.

The product changes color as it cools. Different compositions change color over different temperature changes.

Touching the vial changes the temperature and results in color changes.

Preparation of a cholesteryl ester liquid crystal thermometer.

Materials
Use these materials with normal chemical precautions. Solids should not be inhaled and contact with skin, eyes, or clothing should be avoided. Wash thoroughly after handling.

Cholesteryl oleyl carbonate, Aldrich 15,115-7
Cholesteryl pelargonate (Cholesteryl nonanoate), Aldrich C7,880-1
Cholesteryl benzoate, Aldrich C7,580-2

Different compositions change color over different temperature ranges. The movies above use the composition in the top row of the table.

Cholesteryl oleyl carbonate Cholesteryl pelargonate Cholesteryl benzoate Transition range, degrees C 0.65 g 0.25 g 0.10 g 17-23 0.70 g 0.10 g 0.20 g 20-25 0.45 g 0.45 g 0.10 g 26.5-30.5 0.43 g 0.47 g 0.10 g 29-32 0.44 g 0.46 g 0.10 g 30-33 0.42 g 0.48 g 0.10 g 31-34 0.40 g 0.50 g 0.10 g 32-35 0.38 g 0.52 g 0.10 g 33-36 0.36 g 0.54 g 0.10 g 34-37 0.34 g 0.56 g 0.10 g 35-38 0.32 g 0.58 g 0.10 g 36-39 0.30 g 0.60 g 0.10 g 37-40

---