Introduction to polymers

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Sara Jabbari Farouji

What is a polymer?

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Polymer: refers to molecules consisting of many repeat units (monomers)

Hermann Staudinger !Noble Prize 1953

Macromolecular hypothesis (1920): polymers are molecules made of covalently bonded elementary units called monomers.

Some common polymers

3Polyvinyl chloride

PolyethylenePolystyrene

Polypropylene

Vinyl monomers

Homopolymers and heteropolymers

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Types of polymeric substances

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Liquid-like

Polymer melt

Polymer solution

Solid-like

glassy

Semicrystalline

Amorphous

Network

Liquid crystalline

Examples of polymers in life

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Origin of flexibility in polymers

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Polyethylene

Torsion angle

!Variations of torsion angle is the main source of flexibility

Fully trans polymer

Polymers as random walk

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• Ideal chain models: no interactions between monomers that are far apart along the chain even if they are spatially close to each other.

Polymer configuration & conformation

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Configuration: Conformation:

Structure of repeat units is fixed by the chemical bonds between adjacent atoms

Isomer: Different structures which have identical chemical formulae

3D arrangement of monomers in space defined by sequence of bonds & torsion angles

Can’t be changed without breaking

the bonds !Can be altered through rotation about single bonds.

It depends 1) flexibility of the chain 2) interactions between the monomers on

the chain 3) interactions with surroundings

Characteristic features of a polymer

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• End-to-End distance

• Gyration tensor and radius of gyration

• Hydrodynamic radius

• Form factor (structure factor of a single chain)

References

• Polymer Physics (Chemistry), Rubinstein & Colby

• Scaling Concepts in Polymer Physics, P.G. De Gennes

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Newman projections PE

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