C11 Liquid Crystals (HL)

C11.1 Identify molecules that are likely to show liquid-crystal properties, and explain their liquid-crystal behavior on a molecular level.C11.2 Describe and explain in molecular terms the workings of a twisted nematic liquid crystalC11.3 Describe the liquid-crystal properties of Kevlar, and explain its strength and its solubility in concentrated sulfuric acid.

C11.1 Identify molecules that are likely to show liquid-crystal properties, and explain their liquid-

crystal behavior on a molecular level.

• Molecules that display liquid crystal behavior– biphenyl nitriles

• Nitrile groups make molecules polar

• Biphenyl groups have rigid rod shaped structures

• Long alkaline chains ensure molecule spacing

C11.2 Describe and explain in molecular terms the workings of a twisted nematic liquid crystal

• Twisted Nematic Liquid crystals are the basics of LCD Displays

• Composition of LCD Screen– Polarizing filter– Glass layer– electrodes– Liquid crystal layer– electrodes– Glass layer– Polarizing filter

• Helix Structure of liquid crystals

C11.3 Describe the liquid-crystal properties of Kevlar, and explain its strength and its solubility in

concentrated sulfuric acid.

• Kevlar is lyotropic liquid crystal• Within Kevlar Molecules are Hydrogen

Bonds• Kevlar molecules form strong ring like

structures• Kevlar has a rod-like shape• Kevlar molecules form extra hydrogen

bonds between molecules