Contrast and discuss the difference between amorphous and ...

[tuffie]

Contrast and discuss the difference between amorphous and crystalline regions in a polymer.
 
  What will be an ideal response?

Question 2

Why must average molecular weights be used for polymers rather than exact molecular weights based upon the molecular formula as is done for small molecules?
 
  What will be an ideal response?

Question 3

What is the difference between a number average and a weight average molecular weight?
 
  What will be an ideal response?

[prumorgan]

Answer to Question 1

In crystalline regions the polymer chains are tightly packed which results in a high density. The polymers in these crystalline regions have relatively strong intermolecular bonds which increase the stability of the polymer and increase most mechanical and physical properties. Amorphous regions are zones within the polymer structure where no crystallinity exists. Even highly crystalline polymers usually have some amorphous regions. The physical and mechanical properties for largely amorphous polymers are lower than analogous crystalline polymers.

Answer to Question 2

Small molecules have exact formulas which always apply. In polymers, the chains can be of varying length and so a general formula must be used. This general

formula represents the number of monomer units by an unknown

Answer to Question 3

The number average is dominated by the actual number of molecules and gives equal value to both large and small molecules. The weight average molecular weight gives greater value to the large, heavy molecules.