1. Polymers
A macromolecule is an usually large molecule composed of hundreds of thousands of atoms.
Polymers consists of long chain like molecules called monomers.
Polymers may be classified according to the type of reaction by reaction by which they were formed.
Addition polymers
Condensation polymers

2. Types of Polymers Synthetic Natural Polythene Carbohydrates PVC
Proteins
Polystyrene
Rubber (natural
Nylons
Polyesters
Phenolic resins
Polyurethane
Rubber (synthetic)

3. Types of Polymers (Cont’d)
Addition Polymers
Condensation Polymers
Polyethene
Nylons
PVC
Polyester
Polypropene
Carbohydrates
Polystyrene
Proteins

4. Addition Polymers (Polythene)
When an unsaturated monomer is linked to form a saturated polymer by simply joining up the monomer, addition polymerisation takes place.
This type of polymerisation is generally accomplished by subjecting the monomers (alkenes) to heat and pressure in the presence of a suitable catalyst.
The sequence in the formation of poly(ethene) is shown below:

5. Polythene The low density polythene is soft and flexible.
It’s light enough to float on water and when made in sheets, it is transparent.
It is used to make bags for foods of all sorts, washing up liquid containers and sheets for water proofing and insulation.
One disadvantage of low density polythene however, is that 100°C, it softens so much that it becomes soft and floppy and loses it shapes.
High density polyethane does not lose its shape in hot water and can be used.

6. Addition Polymers
Polychloroethane
Polystyrene

7. Plastics Advantages: Do not corrode in air and water Does not rot
Used as thermal insulators
Lighter and also often cheaper than wood, stone or metals
Some of them are easily bent
Some of them are very strong
Can be moulded easily into almost any shape

8. Plastics (Cont’d) Disadvantages:
Difficult to dispose of. They do not rot away and when they are burnt they produce a thick, dense smoke and poisonous gases
They can be a serious fire hazard. Plastics may burn easily, especially in a fire that is already burning well. Molten plastic can inflict sever burns
They are sometimes not as aesthetic as wood, stone or metal
Because they are cheap, they are often used where wood, stone or metal would be better

9. Linkages Present in Polymers
Ester
Amide
Ether
Alkane

10. Condensation Polymersation
Is a method of joining monomers to form polymers in which all the atoms of the starting materials do not occur in the polymer(s) produced.
Condensation polymers do not have the same composition as the monomers from which they are made.
Two examples of simple condensation reactions are below:

11. Nylon
It is a plastic that can be made into thin fibres which may be woven into cloth, sometimes mixed with synthetic or natural materials.
One type of nylon may be made when solutions of hexanedoic acid and diaminohexane are mixed. This is a condensation polymerisation.
A molecule of water is removed from the 2 molecules and they join together. This is repeated thousands of times to form a polymer chain.

12. Carbohydrates
Are a group of naturally occurring compounds based on the formula Cx(H2O)y i.e they are hydrates of carbon.
The simple carbohydrates are the sugars: glucose and fructose and sucrose and maltose.
Polysaccharides are more complex carbohydrates. They are condensation polymers.
Carbohydrates have a characteristic structural arrangement of atoms within the molecule.

13. Carbohydrates (Cont’d)
Glucose and fructose are called reducing sugars.
Below is the chemical structure of sucrose.

14. Nylon (Cont’d)
This is called nylon 6.6 because the 2 monomer units each contain 6 carbon atoms.
X and Y represent the carbon chains of the monomers (n being any integer).

15. Proteins
Proteins are biological giant molecules which perform a variety of functions.
Examples of proteins are:
Enzymes
Albumin of egg, casein of milk, gluten of flour
Insulin and haemoglobin.
Keratin of wood, fibroin of silk, myosin and collagen of muscle.

16. Formation of Proteins All proteins are built from amino acids.
The amino acid contains 2 reactive functional groups: amino group and acid functional group.
Both these groups participate in condensation reactions leading to the formation of peptide or amide linkages.

17. Formation of Proteins (Cont’d)

18. Hydrolysis of Proteins
The linkages present in proteins may be broken by hydrolysis and the amino acids which form the protein are released.
Hydrolysis can occur by using acids, alkalis or enzymes present in the intestines which hydrolyse proteins to amino acids during digestion.
Chromatography may be used to identify amino acids released by hydrolysis.

19. Terylene Terylene is a polyester because it contains ester linkages.
The formation of terylene by condensation polymerisation is represented below:
X and Y represent the monomer except the functional group.

20. Polysaccharides
These are polymers formed from monosaccharide monomer units by condensation polymerisation.
Polysaccharides contain the -O- linkage. Starch and cellulose are polysaccharides.
On hydrolysis, the polymer breaks up and the monosaccharide is ultimately formed.
The synthesis of simple sugars, can only take place if the organisms contain chlorophyll and sunlight is present.

21. Polysaccharides (Cont’d)
Sucrose is composed of 2 simple sugars.
The release of energy from sucrose by biological systems involves a series of reactions, each of which is catalysed by a given enzyme.
The energy released from sucrose is stored in certin high energy bonds in special molecules until it is needed for a particular chemical reaction in the cell.
One such energy storage is ATP.
The first stage is the hydrolysis of sucrose by enzymes to form glucose and fructose.
This is called digestion and takes place in the digestive tract.

22. Polysaccharides (Cont’d)
The second stage takes place in the cell and involves the breakdown of glucose by a number of separate reactions.
Approx 50 different reactions are involved, each catalysed by a different enzyme.