1
Polymer Materials
Lecture 3: Polymerimzation - 1 Li Oi Lun Helena
School of Mater. Sci. Eng.
Pusan National University
Polymers are large molecules made up of Monomers The synthetic process is Polymerization.
E.g. H C
2 CH2 CH2 CH2
O CH2 CH2 O
Monomer
Polymerization
Polymer
n
Monomer
Polymerization
Polymer
n
Naming of polymer: Poly + monomer name
E.g. Monomer = ethylene, Polymer = polyethylene Monomer = ethylene oxide,
Polymer = polyethylene oxide
Addition (free radical) polymerization
Requires active radicals to start the process
Opening a double bond, eg. Vinyl monomer
1. Initiation – create reactive species by
formation of free radical (unpaired electron) 2. Propagation – Chain grows by addition of
other monomer units
3. Termination – radicals eliminated when they
meet
Growing of polystyrene
4
(a) Active radicals are close to each other
(b) Combination:
become one large chain
OR
(c) Disproportionation:
a hydrogen atom and creation of a double bond
= two different chains
Termination of chain
Examples of Radical Polymerization
H H
H
H H
H CN H
H
H O MeO
H H
H
O Me O
CH2CH
CH2CH CN
CH2CH O OMe C
CH2CH O C O Me
n
n
n
n
Poly(styrene)
Poly(acrylonitrile)
Poly(vinylacetate) Poly(methylacrylate) Monomer
n n
n
n
7
Condensation polymerization
Condensation polymerization: the polymer grows from monomers by giving out a small molecule such as water , carbon dioxide, methanol and etc.
Each monomers in a condensation polymer must have at least two functional groups.
Monomers
• An amine with two groups (diamine).
• An acid with two groups (diacid).
amino carboxyl
The molecules react to form an amide link:
What is given out?
C N
O H
Condensation for amide
Nylon-6,6
Cl Cl
O O
4 H2N NH2
4
Adipoyl chloride 1,6-Diaminohexane
Cl N
H N
H H
O O
4 4
NaOH
HO N
H N
H H O O
4 4
n
6 carbon diacid
6 carbon diamine Nylon-6,6 Diamine, NaOH, in H2O
Adipoyl chloride in hexane
Nylon 6,6
+ nHCl
An ester is formed when an reacts with a acid.
The monomers used to make a polyester are:
• An alcohol with two groups (diol).
• An acid with two groups (diacid).
alcohol carboxylic
hydroxyl carboxyl
What is given out?
Condensation polymerization: Polyethylene terephthalate (PET)
2 alcohol groups = glycol
(ethane-1,2-diol)
Single monomer for
condensation polymerization
12
A monoer with 2 functional groups
13
Condensation polymers
https://www2.chemistry.msu.edu/faculty/reusch/virttxtjml/polymers.htm
Solved problem
Draw the polymer structure for monomers and decide if it is addition polymerization or
condensation polymerization
(a) (b)
14
Solution
(a) condensation (removing H2O) (b) addition
Monomer with tri-functional groups
Monomer with three functional groups E.g. Glycerin (3 –OH groups)
Tends to make nework
(or cross-linked polymers)
15 Thermoset
16
