DoITPoMS

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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!

  1. Which of the following molecules is likely to form a liquid crystalline phase?

    a

    b

    c

    d

Deeper questions

The following questions require some thought and reaching the answer may require you to think beyond the contents of this TLP.

  1. 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?

  2. 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?

  3. 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 ABrush B
    schlierenschlieren

    Yes No a

    Yes No b

    Yes No c

    Yes No d


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