Questions
Quick questions
You should be able to answer these questions without too much difficulty after studying this TLP. If not, then you should go through it again!
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Which of the following molecules is likely to form a liquid crystalline phase?
Deeper questions
The following questions require some thought and reaching the answer may require you to think beyond the contents of this TLP.
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The bright colours found on some insect wings are due to the existence of a thin membrane containing a chiral nematic liquid crystal on their surfaces. Keeping in mind that the light will be reflected by their wings rather than transmitted through them, how do these colours occur?
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In the introduction to this TLP lyotropic liquid crystals were mentioned. Unlike thermotropic species, their properties and mesophases are mainly affected by their concentration in solution, as well as other solutes & solvents present.
Molecules that form lyotropic liquid crystals can usually be thought of as a long-chain molecule with a polar head attached to a non-polar hydrocarbon chain.
What kind of structures do you think these liquid crystals would form when mixed with water? How would this differ if they were mixed with a solvent such as hexane?
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The disclinations shown below all result in a schlieren brush visible under polarised light microscopy. For each disclination, select the brush that would be seen [Yes for Brush A or No for Brush B] (assume the two polarisers are aligned vertically and horizontally)):
Brush A Brush B