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Polymer Overview

Polymer Definition:Open player

Just what is a polymer?

Polymers (gr. poly - many, meros - parts), large molecules with Molecular Weights that are high enough to allow for chain entanglements. Typically Molecular Weight is greater than 5000 g/mole.


Molecular Weight Open player

Surprisingly, the chains may differ from one another in their molecular weight!

Biopolymers most have a descrete MW. Synthertic Polymers all have MW Distributions.

Number average Molecular Weight Picture (162x79, 562 bytes)
Weight average Molecular Weight Picture (286x89, 1001 bytes)
Polydispersity Picture (83x69, 296 bytes)

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Thermal Transitions Listen about Thermal Transitions

Are polymers mostly amorphous, crystalline, or in-between? Also, what is the glass transition temperature?

the Tg of a Rubber band is below RT the Tg of polystyrene is above RT
Thermal Transitions

Glass transition temperature (Tg)

Crystalline transition temperature (Tc)

Melt Transition (Tm)

Decomposition temperature (Td)

Natural Polymers Listen about Natural Polymers

Polymers aren't just synthetic materials, they are also made and used extensively in nature.

Common BioPolymers:

Proteins (Natural Polyamides)

MW = 10,000 to > 1,000,000

examples: wool, silk, us
Chemical structure of a protein
Polysaccharides (Natural Polyamides)

MW = 150,000 to > 1,000,000

examples: cellulose
chemical structure of a Polysaccharide

Natural Rubber

MW = about 1,000,000

examples:

hevea braziliensis (cis) - rubber bands, auto tires.

palaquium oblongifolium (trans) - golf ball cover (gutta-percha)

cis polyisoprene - rubber bands

trans polyisoprene - golf ball cover


Bowling Balls Listen about Bowling Balls

While you can't see the individual atoms, you might be able to see a molecule. Find out why.



Rubber Bands Rubber Bands

Ever wonder why a stretched rubber band returns to its original length when released?

Picture (322x127, 9Kb)

Crosslinked rubber bands are one of the best illustrations of ENTROPY.


Polymer CHEMISTRY Listen about Polymer Chemistry

Polymer CHEMISTRY began with the modification of biopolymers.

1839 - Charles Goodyear: lightly crosslinked rubber - vulcanized

1851 - Nelson Goodyear: heavily crosslinked rubber - ebonite


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© POLYED National Information Center for Polymer Education
University of Wisconsin-Stevens Point
Department of Chemistry
Stevens Point, WI 54481
715-346-3703

 

 

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