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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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