Liquid Crystals

Question 1

Define liquid crystals

Answer 1

Molecules which exhibit moderately strong intermolecular forces

Question 2

Describe the intermolecular forces of liquid crystals

Answer 2

Molecules attracted by intermolecular forces => strong to give: resistance to flow (increased n) and resistance to SA increase (increased y)

Question 3

What affects surface tension in liquid crystals?

Answer 3

y increases with strength of attractive intermolecular forces

Question 4

What affects viscosity in liquid crystals?

Answer 4

n increases with cohesive intermolecular forces

Question 5

Three phases of liquid crystals

Answer 5

• Phases :

1) Nematic - lack layered arrangement, retain parallel alignment
2) Smetic - molecules align in layers
3) Cholosteric - lie in sheets with changing angles between the sheets (chiral nematic)

Question 6

Describe temperature effects on liquid crystals

Answer 6

• Temperature dependence on phase - changes orientation , changes wavelength of reflected light
Increased opacity with degree order