PolymersPolymersHairHair

FurFur

FingernailsFingernails

SilkSilk

CottonCotton

Polyamides(nylons)Polyamides(nylons)

PolyesterPolyester

PolyethylenePolyethylene

PVAPVA

PVCPVC

DacronDacron

LycraLycraWhat are they all?

PolymersPolymers

The word polymerThe word polymer literally literally means "many parts.” means "many parts.”

repeating structural units repeating structural units called monomers.called monomers.

There are both naturally There are both naturally occurring and synthetic occurring and synthetic polymers.polymers.

MerMerMer – Mer –

The repeating unit in a polymer chainThe repeating unit in a polymer chain

Monomer –Monomer – A single mer unit (n=1)A single mer unit (n=1)

Polymer –Polymer –   Many mer-units along a chain (n=10Many mer-units along a chain (n=1033 or more) or more)

Degree of Polymerization –Degree of Polymerization –

The average number of mer-units in a The average number of mer-units in a chain. chain.

There are both naturally There are both naturally occurring and synthetic occurring and synthetic

polymers.polymers.

Naturally Naturally occurring occurring polymerspolymers

proteinsproteinsStarchesStarches cellulose cellulose (plants)(plants)Rubber/latex.Rubber/latex.RNA/DNARNA/DNAcarbohydratescarbohydrates

SyntheticSyntheticPolyethylenePolyethylenePolyvinyl chloridePolyvinyl chloridePolystyrenePolystyrene

Plastics are Plastics are synthetic synthetic polymerspolymers

Synthetic Synthetic polymers remain polymers remain in the environment in the environment for a LONG TIMEfor a LONG TIME

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Different Polymer Different Polymer StructuresStructures

Important Important VocabularyVocabulary

PlastomerPlastomer – bendable polymers – bendable polymers

ElastomersElastomers – Elastic polymers – Elastic polymers

Brittle – Not flexible. Will break, not Brittle – Not flexible. Will break, not bendbend

PolymersPolymersA polymer is a long chain of molecules A polymer is a long chain of molecules that look something like strands of that look something like strands of cooked spaghetti. cooked spaghetti.

If the polymer chains slide past each If the polymer chains slide past each other easily, then the substance acts other easily, then the substance acts like a liquid, because the molecules like a liquid, because the molecules flow.flow.

If the molecules hook together at a If the molecules hook together at a few places along the strand, then the few places along the strand, then the substance behaves like a rubbery substance behaves like a rubbery solid.solid.

Linear Polymer Linear Polymer Structure Structure

Polymers that are bonded Polymers that are bonded in straight lines, form long in straight lines, form long chains or cross-linked chains or cross-linked structures.structures.

Generally high Melting PointGenerally high Melting Pointthermoplasticsthermoplastics

High Density High Density

Strength Depends Strength Depends on Directionon Direction

Tape Experiment Tape Experiment

1.1. Tear tape acrossTear tape across

2.2. Tear tape lengthwiseTear tape lengthwise

Do they tear the same? Why? Do they tear the same? Why?

Branched Branched Structure Structure Monomers branch off a polymer Monomers branch off a polymer

structurestructure

Low Density because they Low Density because they occupy more space occupy more space

Why do Low Density polymers have Why do Low Density polymers have more branches? more branches?

Fewer branches allow the carbon Fewer branches allow the carbon backbones to get close togetherbackbones to get close together

More Branches =More Branches = Fewer Fewer Branches = Branches =

less mass in spaceless mass in space more more mass in spacemass in space

Cross-Linked Cross-Linked Polymer Polymer

Linear polymers are linked Linear polymers are linked together together

Either covalent or hydrogen Either covalent or hydrogen bondsbonds

Hard, brittle, not flexible Hard, brittle, not flexible More cross-links = increase More cross-links = increase strength and stiffnessstrength and stiffness

Entanglement Entanglement When polymer chain (or chains) When polymer chain (or chains)

get tangled get tangled Think of a tangled ball of Think of a tangled ball of stringstringCold pile of spaghetti Cold pile of spaghetti

More entangled = stronger and More entangled = stronger and less flexible less flexible

Review Review To increase To increase StrengthStrength

Increase # of cross-linksIncrease # of cross-linksLots of entanglementsLots of entanglements

To increase To increase DensityDensity Decrease # of branched Decrease # of branched Make linear structures, not branchedMake linear structures, not branched

To increase To increase Flexibility Flexibility Decrease # of branched Decrease # of branched Make linear structures, not branchedMake linear structures, not branchedIncrease temperature Increase temperature

What is going on?What is going on?CROSS – LINKING CROSS – LINKING

Borax is helping PVAs ionically bond Borax is helping PVAs ionically bond togethertogether

Test your Test your knowledgeknowledge

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