2. What are polymers, monomers and
Polymerizations?
What are polymer and polymerization types?
The addition-condensation system
The chain growth-step growth system
Nomenclature of polymers
Homopolymer vs. copolymer
Classification of polymers depending on their
structure
Thermosets vs. Thermopalstics
Introduction to Polymers 2
3. Polymers are macromolecules built up by the linking
together of large numbers of much smaller
molecules.
Introduction to Polymers 3
4. The small molecules which combine with each other
to form polymer molecules are termed monomers.
Introduction to Polymers 4
6. Let CH2-CH2 ≈ 1 inch
Introduction to Polymers 6
Ethylene Polyethylene
Consider only a 200
- mer, Mw ≈ 5600
This ends up with a chain of approximately 1/4 inch (6.4 mm)
in diameter and 1/2 mile (805 m) long.
Molecular weights of 1,000,000 are not uncommon for PE …!
8. The condensation takes place between two
polyfunctional molecules to produce one larger
polyfunctional molecule with the possible
elimination of a small molecule such as water. The
reaction continues until one of the reagents is used
up.
Introduction to Polymers 8
Polymer Structure
The addition-condensation system
9. Introduction to Polymers 9
Adipoyl chloride Hexamethylene diamine
Nylone 6/6
Polymer Structure
The addition-condensation system
10. Addition polymers are those formed from monomers
without the loss of a small molecule.
Introduction to Polymers 10
What are addition polymers?
Y Y
11. The major addition polymers are those formed by
polymerization of monomers containing carbon-
carbon double bond; such monomers are called
vinyl monomers or substituted ethylenes.
Introduction to Polymers 11
Polymer Structure
The addition-condensation system
12. Introduction to Polymers 12
Usually in this type of
polymerization, vinyl
monomers react with
themselves to form polymers
13. What about polyurethane, is it condensation or
addition polymer?
Introduction to Polymers 13
O
CO
CO
NH
ester amide
14. Condensation polymers (New definition)
Introduction to Polymers 14
Polymers whose repeating units are joined
together by functional units such as ester
(-OCO-), amide (-NHCO-), urethane (-OCONH-),
sulfide (-SO2-) and other linkages.
-R-Z-R-Z-R-Z-R-Z-R-Z-
R is aliphatic or aromatic grouping and Z is functional unit.
Polymer Structure
The addition-condensation system
15. There are two major differences between the two
mechanisms:
1. The nature of the species that can react with each
other.
2. The relationship between polymer molecular size and
polymerization conversion.
Introduction to Polymers 15
Polymerization Mechanism
The step-chain polymerization
16. The characteristic of chain polymer is that polymer
growth takes place by monomer reacting only
with the reactive centers. Monomer does not
react with monomer and the different-sized
species such as dimer, trimer, and n-mer do not
react with each other. Polymerization ceases
when the active centre destroyed by termination
reaction(s).
Introduction to Polymers 16
Chain polymerization
17. Introduction to Polymers 17
Chain polymerization – anionic polymerization of
styrene
But, the following is NOT possible
18. In step polymerization each polymer formed can
react further with monomer or other polymers.
Each dimer, trimer, etc. is just as reactive as
monomer. By this mechanism, the size of the
polymer molecules increases slowly.
Introduction to Polymers 18
Step polymerization
19. Introduction to Polymers 19
Step polymerization – the production of poly
(ethylene terephthalate) (PET)
20. Introduction to Polymers 20
Step polymerization – the production of poly
(ethylene terephthalate) (PET)
Next steps:
Or……..
22. Most simple and frequently used
It is applicable to polymers synthesized from a
single monomer as in addition and ring-opening
polymerizations.
How to name:
simple monomers: add monomer name to the
prefix poly without space or hyphen.
Introduction to Polymers 22
Nomenclature based on source
23. simple monomers
Introduction to Polymers 23
Nomenclature based on source
Ethylene Polyethylene
Acetaldehyde Polyacetaldehyde
24. Monomers have multiword name or abnormally long
name: parenthesis are placed around its name
following the prefix poly
Introduction to Polymers 24
Nomenclature based on source
3-methyl-1-pentene Poly (3-methyl-1-pentene)
Propylene oxide Poly(propylene oxide)
Clorotriflouroethylene Poly(clorotriflouroethylene)
25. Note: condensation polymers synthesized from single
reactants are named in a similar manner.
Introduction to Polymers 25
Nomenclature based on source
6-aminocaproic acid Poly(6-aminocaproic acid)
26. Homopolymers are polymers composed of only one
repeating unit in their molecules.
Introduction to Polymers 26
What are homopolymers?
What are copolymers?
Copolymers are polymers composed of two different
repeating units in their molecules.
Such as
Styrene
Acrylonitirle
Be careful !!!
27. Introduction to Polymers 27
Types of copolymer systems
Random copolymer -AABABBBABBAAAA-
Alternating copolymer -ABABABABABABAB-
Block copolymer -AAA-BBBBBB-AAAA-BB-
Graft copolymer
28. Linear polymers
Introduction to Polymers 28
What if polymerization conditions are changed or
different monomer is used, e.g. ethylene vs.
butadiene?
29. Branched polymers
Introduction to Polymers 29
What is the effect of branching on polymer
properties?
Crystallinity
Is it branched polymer?!!!
30. Cross-linked polymers
Introduction to Polymers 30
Using appropriate monomers
Chemical reactions
Polymer molecules are connected together at points
other than their ends
Crosslinked polymers do not dissolve but can be swelled
by liquids.
Light crosslinking improves elasticity properties
polymer is used as rubber
High degree of crosslinking gives high rigidity and
thermal stability (high melting point).
BOTH CROSSLINKED POLYMERS CANNOT BE RECYLED
OR REPOROCESSED
31. Cross-linked polymers
Examples
Introduction to Polymers 31
Show the polymer formed by the reaction of the following monomers.
Is the resulting polymer linear or branched/cross-linked?
Solution
32. Cross-linked polymers
Examples
Introduction to Polymers 32
Show the polymer formed by the reaction of the following monomers.
Is the resulting polymer linear or branched/cross-linked?
Solution
33. What are thermoset polymers?
Introduction to Polymers 33
Polymers that will not flow when heated. Thermosets
have cross-linked structure. Examples are phenolic
and epoxy resins.
What are thermoplastic polymers?
Polymers that soften, without chemical change, and take
new shapes by the application of heat and pressure
and harden when cooled. Thermoplastics have linear
and branched structures. Examples are PP, PVC and
Nylon
34. Introduction to Polymers 34
Plastics
Thermosets Thermoplastics
Amorphous Crystalline
Highly
cross-linked
Lightly
cross-linked
Classification of polymers – polymer structure
