Modern MaterialsModern Materials

BLB Chapter 12BLB Chapter 12

12.1 Liquid Crystals12.1 Liquid Crystals Solid Solid → liquid crystal → liquid→ liquid crystal → liquid Liquid crystals – exhibit properties of both liquids Liquid crystals – exhibit properties of both liquids

and crystalline solidsand crystalline solids Ordered arrangementOrdered arrangement Viscous liquid, non-solidViscous liquid, non-solid

Types of liquid crystal phases:Types of liquid crystal phases:

Examples of MoleculesExamples of Molecules

Long in comparison to widthLong in comparison to width Flat benzene rings aid in stackingFlat benzene rings aid in stacking End polar groups promote allignmentEnd polar groups promote allignment

Applications of Liquid CrystalsApplications of Liquid Crystals

Temperature monitorsTemperature monitors LCDsLCDs

12.2 Polymers12.2 Polymers

““many parts”many parts”Large, high molecular weight molecular Large, high molecular weight molecular

compoundscompoundsFormed by joining monomers together Formed by joining monomers together

through polymerizationthrough polymerizationExamples: plastic, DNA, proteins, starch, Examples: plastic, DNA, proteins, starch,

rubberrubber

Types of PolymerizationTypes of Polymerization1.1. Addition – monomers are added together Addition – monomers are added together

forming bonds between themforming bonds between them

2.2. Condensation Polymerization – monomers are Condensation Polymerization – monomers are joined with the elimination of a small molecule joined with the elimination of a small molecule such as watersuch as water

N

H

H H O C

O

+ N

H

C

O

H O H+

Production of proteins: (See p. 1013)

More about PolymersMore about Polymers

Types of plasticTypes of plasticThermoplasticThermoplasticThermosetThermosetElastomerElastomer

CrystallinityCrystallinityBranchingBranchingCross-linkingCross-linking

Natural rubber

Vulcanized rubber(Goodyear, 1839)