Question

This is a post lab question for my organic chemistry 1 lab course and I just cannot seem to find the answer

Our lab is preparation and observation of a temperature- dependent liquid crystal display. We melted cholesteryl pelargonate and cholesteryl oleyl carbonate together between two microscope slides and observed the blue/irridescence color that appeared.

post lab question i need help with:

if your liquid crystal mixture is iridescent at about 15 degrees Celcius, how would you change the method so that iridescence is observed at about 25 degrees celcius?

Answer 1

To change the iridescence to be observed at 25 degrees celsius, you need to change the composition of the mixture of the compounds taken to make the LCD. You need to take them 1:1, which means equal quantities of both the compounds to see the same at 25 oC. The reason is that both the molecules are of different sizes. So, when you change the quantities, you are ultimately changing number of molecuules of each. So, you have changed the packing of the molecules, which will reflect light at different temperature.