Polymer Overview

Polymer Definition

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

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

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

 
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

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

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