1. CLASSIFICATION OF POLYMERIZATION REACTIONS
For polymerization it is required that the monomer molecule is capable of being linked to two (or more) other molecules of monomer by chemical reaction (functionality). 
Functionality of two or higher is needed.
Classification of polymerization are based on comparison of the molecular formed of a polymer with that of the monomer from which it was formed.

2. CONDENSATION POLYMERIZATION
Those which yield polymers with R.U. having less atoms than present in the monomers from which they formed (elimination of a small molecule).
Example
Polyester is a typical condensation reaction between bifunctional monomers with elimination of water.
X HO-R1-OH + X HOCO-R2-COOH
HO [ R1-OCO-R2-COO ]x H + (2X-1) H2O

3. ADDITION POLYMERIZATION
Those which yield polymers with repeat units having identical molecular formula to those of monomers from which the one formed.
 Example
 Polystyrene.
X CH2 = CH CH2-CH-CH2-CH---, etc.

4. The addition reaction mechanisms are result from chain reactions involving some sort of active center. 
Because condensation reaction mechanisms are usually formed by the step wise intermolecular condensation of reactive groups.
And because some condensation process reacted in addition manner a new term is used to defined this process (step reaction or condensation polymer).
See table Billmeyer

5. Step Polymerization Linear Step Polymerization
Step polymerization involves successive reaction between pairs of maturely-reactive functional groups.
Functionality is a critical importance in this reaction
Example
1)Condensation reaction of carboxylic acid groups with hydroxyl groups both acetic acid and ethyl alcohol are monofunctional compounds which yield ethyl acetate with elimination of water
CH3COOH +CH3CH2OH CH3COOCH2CH3 + H2O
From this polymer chain can not form.

6. 2)If we have terephthalic acid and ethylene glycol both are difuctional
COOH CH2-OH COOCH2-CH2-OH
H2O
COOH CH2-OH COOH
The product is an ester which have one carboxylic acid end group and one hydroxyl end-group (i.e. it is also difunctional).

7. Tetephtalic acid react with glycerol HO CH2CH (OH) CH2OH
The dimers can react with molecules of acid or alcohol or dimer formation of difuctional.
Difunctional monomers linear step polymerization.
Trifunctional monomers branched polymer.
Example
Tetephtalic acid react with glycerol
HO CH2CH (OH) CH2OH 
The product is non linear.

8. POLYCONDENSATOIN
Step polymerization that involve reaction in which small molecules are eliminated are termed polycondensation.
Example
(1) the formation of linear polyesters 
n HOOC-R1 - COOH + nHO-R2- OH
H [ OOC-R1-COOR2 ]n OH + (2n-1) H2O
Where R1 and R2 general groups.
It can be represented as R1A2 + R2B2
where:
A & B are mutually reactive groups.

9. Polyesters may also prepared from single monomer which contain both types of functional group. Example w-hydroxyl carboxylic acids.   HOOC-R-OH   This is ARB step polymerization Advantage exact stoiciometric equivalent of the two functional groups is granted.

10. POLYAMIDES
Polyamides are prepared by polycondensation of amine groups.
Example
nH2N-R1-NH2 + nHOOC-R2-COOH
H [ NH-R1NHOC-R2-CO ]n OH + (2n-1) H2O

11. POLYETHERS Polyethers formed by dehydration of dioles.
HO-R-OH + HO-R-OH HO [ RO ]n H +
(n-1)H2O
RA2 step polymerization

12. SILOXANE
Siloxane Prepared by hydrolysis of dichloro dialkylsiloxanes e.g. dichlorodimethylsiloxene.  
CH CH3
nCl-Si-Cl + (n+1) H2O HO [ Si-O ] H   + 2nHCl
CH CH3
(poly dimethylsiloxane) (PDMS)
initially hydrolysis occurs
CH CH3
Cl-Si-Cl H2O HO-Si-OH +2HCl 
after that 
we can have both RA2 + RB2 polymerized
(CH3)2 SiCl2 react with (CH3)2 Si(OH)2 or
(CH3)2 Si(OH2) can condense by itself (RA2) polymer.

13. POLYADDITION
Step polymerization in which the monomers react together without the elimination of other molecules.
Example
1) Polyurethanes by the RA2 + RB2 reaction of diisocyanate with diols.
O = C = N = R1 - N = C = O + HO - R2 - OH
O O 
[ C - NH-R1 - NH-C - OR2-O ]n

14. 2) Polyureas O O C - N - R1 - N = C + H2N - R2-NH2 O O
[ C - NH-R1 - NH-C-NH-R2-NH ]n

15. Thank You
See You Next Lecture