Polymer Overview

Polymer Definition

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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

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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
Weight average Molecular Weight
Polydispersity

Thermal Transitions

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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
 


 
Glass transition temperature (Tg)
 
Crystalline transition temperature (Tc)
 
Melt Transition (Tm)
 
Decomposition temperature (Td)





 

 


 

 

Natural Polymers

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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
 




Polysaccharides (Natural Polyamides)
MW = 150,000 to > 1,000,000
examples: cellulose
 
 
 
Natural Rubber

 

MW = about 1,000,000
 
examples:
 
hevea braziliensis (cis) - rubber bands, auto tires.
 
palaquium oblongifolium (trans) - golf ball cover (gutta-percha)
 
 
 
 
 
 
 

Bowling Balls

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

Rubber Bands

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Ever wonder why a stretched rubber band returns to its original length when released?
 
 
Crosslinked rubber bands are one of the best illustrations of ENTROPY.

Polymer Chemistry

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Polymer Chemistry began with the modification of biopolymers.
1839 - Charles Goodyear: lightly crosslinked rubber - vulcanized
1851 - Nelson Goodyear: heavily crosslinked rubber - ebonite