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.
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
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.
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 2.1 Billmeyer

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.

2)If we have terephthalic acid and ethylene glycol both
are difuctional
COOH
CH2-OH
COOCH2-CH2-OH
+
COOH
+ H2O
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).
The dimers can react with molecules of acid or alcohol
or dimer.
formation of difuctional.
Difunctional monomers
Trifunctional monomers
linear step polymerization.
branched polymer.
Example
 Tetephtalic acid react with glycerol
 HO CH2CH (OH) CH2OH
 The product is non linear.

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.
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.
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
POLYETHERS

Polyethers formed by dehydration of dioles.
HO-R-OH + HO-R-OH
(n-1)H2O
RA2 step polymerization
HO [ RO ]n H +
SILOXANE

Siloxane Prepared by hydrolysis of
dialkylsiloxanes e.g. dichlorodimethylsiloxene.
CH3
nCl-Si-Cl + (n+1) H2O
CH3
dichloro
CH3
HO [ Si-O ] H + 2nHCl
CH3
(poly dimethylsiloxane) (PDMS)
initially hydrolysis occurs

CH3
Cl-Si-Cl + 2H2O
CH3
CH3
HO-Si-OH +2HCl
CH3
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.
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

2) Polyureas
O
O
C - N - R1 - N = C + H2N - R2-NH2
O
O
[ C - NH-R1 - NH-C-NH-R2-NH ]n
Thank You
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