Thermotropic LC’s – A Reminder

Lyotropic Liquid Crystals

• Molecules usually amphiphilic – hydrophobic and hydrophilic parts.

• How will these behave around water?

Hydrophilic head

Hydrophobic tail

Interaction With Water

• Orientational order induced by addition of solvent.

• Hydrophilic heads of the molecules are attracted to the water.

• What will the hydrophobic tails be attracted to?• What shapes may form?

One option…

• The exact shape formed will depend on the concentration and temperature.

Lyotropic Liquid Crystal Phases

Lyotropic LC’s in Nature

• Common in biological systems e.g. cell membranes.

How About Bubbles

• Soap bubbles are made of surfactants (amphiphilic) and water.

• How do the water and surfactants arrange themselves in a bubble?

What About Colour?

• Light can reflect on the inner or the outer bubble surface.

• Reflected light can interact constructively or destructively.

http://www.webexhibits.org/causesofcolor/15E.html

More on Colour

• The observed colour depends on thickness.• Where is the soap mixture the thinnest?