Preparation of Cholesteryl Ester Liquid Crystals

One of the principal advantages of liquid crystals is their ability to map out thermal regions of different temperature. These cholesteric-nematic liquid crystals reversibly change color as the temperature changes. As long as the mixture is stored in a sealed container it can be prepared months in advance, although the sample may need to be remelted to mix.

Safety

Wear eye protection

Procedure

Step 1. Place 0.65 g cholesteryl oleyl carbonate, 0.25 g cholesteryl pelargonate, and 0.10 g cholesteryl benzoate in a vial.

Step 2. Melt the solid in a sample vial using a hair drier, heat gun, or oven.

Step 3. While the mixture is still liquid, divide into several vials.

Step 4. The product changes color as it cools. Different compositions change color over different temperature changes.

Step 5. Touching the vial changes the temperature and results in color changes.

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
• 0.01 g balance, vials, heat gun or hair dryer

	Cholesteryl oleyl carbonate	Cholesteryl pelargonate	Cholesteryl benzoate	Transition range, degrees C
Different compositions change color over different temperature ranges.	0.65g	0.25g	0.10g	17-23
	0.70g	0.10g	0.20g	20-25
	0.45g	0.45g	0.10g	26.5-30.5
	0.43g	0.47g	0.10g	29-32
	0.44g	0.46g	0.10g	30-33
	0.42g	0.48g	0.10g	31-34
The movies above use the composition in the top row of the table.	0.40g	0.50g	0.10g	32-35
	0.38g	0.52g	0.10g	33-36
	0.36g	0.54g	0.10g	34-37
	0.34g	0.56g	0.10g	35-38
	0.32g	0.58g	0.10g	36-39
	0.30g	0.60g	0.10g	37-40

 

YouTube Link:

http://www.youtube.com/watch?v=Q_Yem5v8JrI

Liquid Crystals Pages