This document discusses polymers, including their classification, characteristics, properties, strengths, and applications. It begins with an introduction to polymers being long chains of repeating monomer units. It then covers the main topics of types of polymers like polyethene and nylon, how they are classified based on composition and reaction, their characteristics like low density and good moldability. Properties depend on chain length and structure. Strength increases with longer chains and higher crystallinity. Finally, applications of polymers in areas like packaging, textiles, construction, medicine and pharmaceuticals are outlined.

1. POLYMERS and their PROPERTIES
►Introduction
►Basic Topics:
 Types of Polymers
 Classification of Polymers
 Characteristics of Polymers
 Properties of Polymers
 Strength of Polymers
►Applications of Polymers

2. Introduction
► Polymers are long chain giant organic molecules are
assembled from many smaller molecules called
monomers. Polymers consist of many repeating
monomer units in long chains. A polymer is analogous
to a necklace made from many small beads
(monomers).
► Another common name for many synthetic polymers is
plastic which comes from the Greek word "plastikos",
suitable for molding or shaping. Many objects in daily
use from packing, wrapping, and building materials
include half of all polymers synthesized.

3. Basic Topics:
 Types of Polymers
 Classification of Polymers
 Characteristics of Polymers
 Properties of Polymers
 Strength of Polymers

4. Types of Polymers
► Polythene
The first commercially produced polymer is also the simplest and most
common: polythene. Its systematic name is poly(ethene) meaning it is a
polymer made from the monomer, ethene. Ethene is a small molecule
containing two carbon atoms linked by a double bond and four hydrogen
atoms, two bonded to each carbon.
► Free Electrons
When ethene is subjected to high temperature and pressure, or reacted in the
presence of a catalyst, one of the bonds in the double bond is broken. Each of
the carbon atoms then has a free electron which can form a covalent bond by
pairing with another free electron. If other ethene molecules are present, the
double bond in one of them can break, and the free electron on one of the
carbons can combine with another on the original molecule. As this continues,
a long chain of carbon atoms, bonded to one another by single covalent bonds
forms. Each carbon atom has two hydrogen atoms bonded to it.

5. ► Poly(propene)
Other polymers can be made in this way. Poly(propene) is very
similar to poly(ethene). It is made from propene which has three
carbon atoms, two of which are joined by a double bond. When it
reacts to become a polymer (polymerises), the long chain is
similar to poly(ethene) except that every other carbon atom has a
methyl (CH3-) group attached to it.
► Varied Uses
The properties of this type of polymer depend on the regularity of
the arrangement of the chains. If they are lined up in a regular
way, they are strong, hard materials. If they are more irregular, or
there are more side-chains on the molecules, they are more
flexible.

6. ► Amide Linkages
One of the most common molecules in biochemistry is a type of polymer
called protein. These are made up from monomers known as amino acids and
they are joined by an amide linkage. These linkages are made by a carboxylic
acid group (-COOH) reacting with an amine group (-NH2) forming the
linkage (-NHCO-) and eliminating water. This linkage is the basis of another
type of synthetic polymers, the Nylons.
► Nylon
Whereas proteins use monomers with both a carboxylic acid and an amine in
the same molecule. Nylons are made using two types of monomer. These are
dicarboxylic acids and diamines. The first nylon synthesised used one
monomer with a chain of four carbons with a carboxylic acid group on each
end and another monomer with a six carbon chain with an amine group on
each end. This produced a polymer with repeating units of six carbons joined
with amide linkages, but alternately reversed. This polymer is Nylon-6.6.
Nylons are mainly used as fibres for clothing and also other hard parts in light
engineering.

7. ► Polyurethane
A further important group of polymers are polyurethanes. These
are very similar to nylons, but are formed by reacting alcohols
with isocyanates and have an amide linkage with an additional
oxygen atom in the chain. These polymers are softer and more
elastic than nylons and are used as a substitute for rubber and in
elastic and Lycra.
► Polyesters
The final types of polymer we will deal with in this article are the
polyesters. The ester linkage is a carboxylic acid group where the
hydrogen has been replaced by the carbon of another organic
group. Polyesters are widely used as fibres for clothes and also
for many drinks bottles. They are also used to make thin films for
applications such as video tape.

8. Classification of Polymers
►Homopolymers - consist of chains with identical
bonding linkages to each monomer unit. This
usually implies that the polymer is made from all
identical monomer molecules.
These may be represented as : -[A-A-A-A-A-A]-
►Copolymers - consist of chains with two or more
linkages usually implying two or more different
types of monomer units.
These may be represented as : -[A-B-A-B-A-B]-

9. Polymers are further classified by the
reaction mode of polymerization, these
include:
►Addition Polymers - the monomer molecules
bond to each other without the loss of any other
atoms. Alkene monomers are the biggest groups
of polymers in this class.
►Condensation Polymers - usually two different
monomer combine with the loss of a small
molecule, usually water. Polyesters and
polyamides (nylon) are in this class of polymers.
Polyurethane Foam in graphic.

10. Classification based upon the physical
property related to heating:
►Thermoplastics - plastics that soften when
heated and become firm again when cooled. This
is the more popular type of plastic because the
heating and cooling may be repeated.
►Thermosets - plastics that soften when heated
and can be molded, but harden permanently.
They will decompose when reheated. An
example is Bakelite, which is used in toasters,
handles for pots and pans, dishes, electrical
outlets and billiard balls.

11. Characteristics of Polymers
► Low Density.
► Low coefficient of friction.
► Good corrosion resistance.
► Good mould ability.
► Excellent surface finish can be obtained.
► Can be produced with close dimensional tolerances.
► Economical.
► Poor tensile strength.
► Low mechanical properties.
► Poor temperature resistance.
► Can be produced transparent or in different colors.

12. Properties of Polymers
The physical properties of a polymer, such as its strength
and flexibility depend on:
► Chain length - in general, the longer the chains the
stronger the polymer;
► Side groups - polar side groups give stronger attraction
between polymer chains, making the polymer stronger;
► Branching - straight, un branched chains can pack
together more closely than highly branched chains,
giving polymers that are more crystalline and therefore
stronger;
► Cross-linking - if polymer chains are linked together
extensively by covalent bonds, the polymer is harder
and more difficult to melt.

13. Strength of Polymers
In general, the longer the polymer chain, the stronger the
polymer. There are two reasons for this:
► longer chains are more tangled
► there are more intermolecular forces between the chains
because there are more points of contact. These forces,
however, are quite weak for polyethene.
► Areas in a polymer where the chains are closely packed in
a regular way are said to be crystalline. The percentage
of crystallinity in a polymer is very important in
determining its properties. The more crystalline the
polymer, the stronger and less flexible it becomes.

14. ► When a polymer is stretched (cold-drawn), a neck forms. In
the neck the polymer chains line up producing a more
crystalline region. Cold-drawing leads to an increase in
strength.
► The first polyethene which was made contained many
chains which were branched. This resulted in a relatively
disorganised structure of low strength and density. This was
called low density polyethene (ldpe).
► In the crystalline form, the methyl groups all have the same
orientation along the chain. This is called the isotactic
form. In the amorphous form, the methyl groups are
randomly orientated. This is called the atactic form.
► Polymers with a regular structure are said to be
stereoregular.

15. Applications of Polymers:
► Polymeric materials are used in and on soil to improve
aeration, provide mulch, and promote plant growth and
health.
Medicine
► Many biomaterials, especially heart valve replacements
and blood vessels, are made of polymers like Dacron,
Teflon and polyurethane.
Consumer Science
► Plastic containers of all shapes and sizes are light weight
and economically less expensive than the more traditional
containers. Clothing, floor coverings, garbage disposal
bags, and packaging are other polymer applications.

16. Industry
►Automobile parts, windshields for fighter planes,
pipes, tanks, packing materials, insulation, wood
substitutes, adhesives, matrix for composites, and
elastomers are all polymer applications used in the
industrial market.
Sports
►Playground equipment, various balls, golf clubs,
swimming pools, and protective helmets are often
produced from polymers.

17. Polymers in the Pharmaceutical
Applications
►blood substitutes (polymersomes), drug
delivery and therapeutic systems, in the
synthesis of macromolecular prodrugs and
in the technology of prolonged release drug
formulations

18. Polymers with the pharmacological effects and
polymeric blood substitutes
►DIVEMA, copolymer of divinyl ether-maleic
anhydride: antitumoral and antiviral
properties
►Methylcellulose: swelling, relaxation and
sliding agents as not absorbed through GIT
►copolymer of ethylene and propylene
glycols: Laxative
►non-ionic, surface active polymer: not
penetrate through GIT so use for hydration
of stercorous mass, reduce friction

19. Polymers with the pharmacological effects and
polymeric blood substitutes
►linear polymer of uronic acids - alginic acid:
antacid
►Polyvinylpyrrolidone: anti-diarrhoeal
►Corticotrophins: Rheumatoid and asthma
► peptide antibiotics

20. ► therapeutic agent
could be
incorporate into
polymer chain,
might be end-
capped or may form
a pendant group of
the macromolecular
chain
Macromolecular prodrugs

21. Polymers in the technology of prolonged
release drug formulations
►absorption of the therapeutic agent using
prolonged release drug forms can be
reduced by coating, incorporation,
complexation or bonding on the ionites
►biodegradable and non-biodegradable

22. Polymers in the therapeutic systems
technology