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What is a polymer? A long molecule

made up from lots ofsmall moleculescalledmonomers

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naturally occurring polymers Polymers that exist in plants or animals Types of naturally occurring polymers

protein : muscles

carbohydrates : cellulose

natural rubber : latex

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synthetic polymers Polymers made in industry from chemicalsubstances Scientists are able to copy structures ofnatural polymers to produce syntheticpolymers trough scientific research

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synthetic polymers many of raw materials for synthetic polymers areobtain from

-> petroleum types of synthetic polymers

plastics

fibers

elastomers

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same monomer... Monomers all sametype (A) A + A + A + A-A-A-A-A- eg poly(ethene)polychloroethene PVC

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Different monomers... Monomers of twodifferent types A + B + A + B -A-B-A-B- Eg polyamides,Polyesters

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Polymerisation

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Addition Polymerisation A carbon carbon double bond is needed in themonomer A monomer is the small molecule that makes up

the polymer

C C

H

H

H

Hn

ethene

high pressure/trace O2catalyst C C

H

H

H

Hn

poly(ethene)

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Addition Polymerisation The polymer is the only product Involves the opening out of a double bond The conditions of the reaction can alter theproperties of the polymer Reaction proceeds by a free radical mechanism Oxygen often used as the initiator

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Addition polymerisation The board specifies that you know this additionpolymerisation reaction

C CH H

HC

H

C C C

H H

H H H

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Addition polymerisation Conditions are high pressure and an oxygeninitiator (to provide the initial free radical). Monomer = phenylethene Polymer = poly(phenylethene)

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Prediction the repeating unit This is easy, basically open out the doublebond.

C C

H

H

Cl

H

chloroethene

C C C C

H H H H

H HCl Cl

poly(chloroethene) aka

polyvinylchloride (pvc)

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Stereoisomerism in Additionpolymers. Ziegla and Natta in the 1950s cam up with a wayof controlling the repeating unit. They won a Joint Nobel prize for their work The polymerisation process can be controlled used a

tin/aluminium catalyst at 50C and 1.5atm

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Stereoisomerism in Additionpolymers.

Previous to this only one type of poly(ethene) couldbe made, called LDPE or low density poly(ethane). The chains formed a tangled mass. HDPE could now be produced. This has a much stiffer structure due to areas of

crytallinity where the polymer chains are muchmore ordered.

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Continues... HDPE has a much higher boiling point due to thesemore ordered regions. Generally used to make plastic bottles. Ziegler and Natta also discovered that they couldmake stereo regular polymers. Isotactic,syndiotactic and atactic.

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Condensation Polymers Involves 2 monomers that have different functionalgroups. They also involve the elimination of water oranother small molecule. Hence the term condensation polymer. Monomer A + Monomer B Polymer + smallmolecule (normally water). Common condensation polymers include polyesters(the ester linkage) and polyamides (the amidelinkage as in proteins).

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Polyesters The OCR example here is terylene, a polymer ofbenzene-1,4-dicarboxylic acid and ethane-1,2-diol. The ester linkage is formed between the monomers

C

O

O

the ester linkage

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Polyesters You need to be able to reproduce the formation ofterylene, and possibly predict the structures of otherpolyesters

HO C

O

C

O

OHn + HO CH2 CH2 OHn

heat with

an acid

catalyst

C

O

C

O

O CH2 CH2 O

poly(ethan-1,2-diyl benzene-1,4-dicarboxylate)

n

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Polyamides These involve the linkage of two monomers throughthe amide linkage as in proteins (e.g. silk)

C

O

N

H

the amide linkage

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Nylon 6,6 a polyamide

N (CH2)6 N

H

H

H

H C

O

OH(CH2)4HO

O

C

1,6-diaminohexane hexanedioic acid

N (CH2)6

H

N

H

C

O

(CH2)4 C

O

part of a nylon polymer chain

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Kevlar a polyamideNH2H2N C

O

HO

(CH2)4 C

O

OH

N N C (CH2)4 C

OO

H H

part of the kevlar polymer chain

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Uses of polyamides The main use of polyesters and polyamides is asfibres in clothing. Most clothing now has a degree of manufacturedfibres woven into the natural material (such as

cotton). This gives the material more desirablecharacteristics, such as stretchiness, and betterwashability. Dont forget that proteins are also polyamides, youmust know how the linkage works with naturalpolymers such as proteins.

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Thermoplastics (80%)

No cross links between chains. Weak attractive forces between chains broken

by warming. Change shape - can be remoulded. Weak forces reform in new shape when cold.

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Thermosets

Extensive cross-linking formed bycovalent bonds. Bonds prevent chains moving relative toeach other. What will the properties of this type ofplastic be like?

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Longer chains make strongerpolymers. Critical length neededbefore strength increases.

Hydrocarbon polymersaverage of 100 repeatingunits necessary but only40 for nylons. Tensile strength measuresthe forces needed to snap a

polymer. More tangles + moretouching!!!

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Properties of plastics Light strong malleable inert to chemical insulators of electricityand heat

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Properties of plastics Strong Inert to chemical attacks Easily molded or shaped and be colored Cheap Able to resist corrosion Special properties can be made according to specificneeds

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Environmentalpollution !!!

Most of the polymers are non-biogradeable Cannot be decomposed by bacteria / decomposer So caused disposal problem when polymernot decay

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Environmentalpollution !!!

Polymer containers not buried in the ground Become breeding ground for mosquitoes So caused diseases such as dengue

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Environmentalpollution !!! The non-biogradeable polymers thrown into rivers -> lakes -> seas Swallowed by aquatic animals Animals die due to chocking

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Environmentalpollution !!!

Open burning of polymers Released harmful, poisonous gases Cause air pollution Contributes to acid rain problem

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Ways to dispose syntheticpolymer properly PYROLISIS-burn without oxygen INCINERATION-gas is filtered INVENT A BIODEGRADEABLE SYNTHETICPOLYMER

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CATEGORY Code Example DENSITY

1 PETE Pop bottle

Peanut butter jar

Mylar

1.381.39

2 HDPE Milk jug

Shampoo bottle

0.950.97

3 V Pipes and fittings, pill bottles,

shower curtains, garden

hoses, tile, leather like

luggage and upholstery

1.151.35

4 LDPE Trash bags

Diaper liners

0.920.94

5 PP Indoor/outdoor carpeting,

kitchenware

0.900.91

6 PS Styrofoam

Pen casing

Clear plastic cups

1.051.07

7 OTHER Toothpaste and cosmetic containers

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Possible Questions!!! What is a monomer? Explain polymerization and its types? Examples of polymers? Classification of polymers. What are thermosets and thermoplastics? Explain the structural differences betweenthermosets and thermoplastics? What are the effects of heat and force onthermoplastics and thermosets? Differntiate thermosets and thermoplastics. Properties and limitations of plastics What are different additives? Classification of additvies and its properties List the polymers used in automobile.