Polymers Polymers

C.X.C objectives Students should be able to : Define polymers Distinguish between addition and condensation as reactions in

the formation of polymers Name examples of polymers formed by: (i) addition reactions (ii)condensation reactionso Draw diagrams to represent the formulae of monomerso State at least one use of each of the following types of polymers :

(i) polyalkene (ii) polyamide (iii) polyester (iv) polysaccharideo Show how the monomers are linked in the structure of a polymer o Demonstrate the differences in properties between a monomer

and the polymer it forms.

Mind Map

Polymers Obj 1. Students should be able to define polymers :

What is a polymer ?

Polymers are macromolecules formed by linking together thousands of small molecules called monomers, usually in chains. Polymers are formed by polymerisation.

Some polymers occur naturally whereas some are man-made (synthetic). Synthetic polymers are referred to as Plastics but will be further discussed later in this module.

Polymerisation Obj. 2. Distinguish between addition and condensation as

reactions in the formation of polymers.

Polymerisation is the process whereby a polymer is formed from monomers. This can happen in two ways.

Addition Polymerisation

Condensation Polymerisation

Occurs when unsaturated monomers are linked to form a saturated polymer.

Occurs when monomers join with the elimination of a small molecule e.g. water from between each unit.

Addition Polymerisation An addition polymer is constructed of one type

of monomer. This is an unsaturated molecule (usually an alkene C C )

Addition polymers are referred to as Polyalkenes.

The polymer is formed when the double bond breaks and the units join together .

Only one type of product is formed.

Naming Polymers To name a polymer, the prefix ‘Poly’ is

placed before the name of the monomer.

For example: Polypropene Polystyrene Polyethene

Addition Polymers Polyalkenes have properties of substances commonly

named PLASTICS. Plastics are synthetic polymers.

Name of Polymer UsesPolythene Packaging, plastic bags, plastic

wraps.Polyvinylchloride Raincoats, plumbing fittings,

water pipes, insulation of electric wires.

Polypropene Plastic containers, food containers, coolers.

Teflon Non-stick coatings for irons and pots.

Perspex Glass substitute in aircraft windows, reflectors on vehicles and sign boards.

Condensation Polymerisation

Condensation polymerisation describes a process whereby the polymer is formed when monomer units join together with the elimination of a small molecule, usually BUT NOT ALWAYS water. (HCl or NH3 could be eliminated as well.)

In order for monomers to form condensation polymers, the monomer must have two active sites ( point at which the monomers join).

Two products are formed as a result of this type of polymerisation.

It is important to note that a condensation polymer can have monomers of one or two types.

Condensation Polymerisation There are two types of condensation

polymerisation.

Natural Condensation polymers e.g protein and

starch

Synthetic or man-made

condensation polymers e.g.

nylon and terylene

Types of linkage Condensation polymers can be divided into groups based

on the type of linkage between the monomer units.

Polyamides – Amide Linkage Polyesters- Ester Linkage C O

Polysaccarides- Saccaride Linkage O

Types of condensation polymers

Polyamides

Polyesters

Polysaccharides

Polyamides Protein is a natural polyamide. The

monomers which make up proteins are amino acids.

Polyamides cont’d : Two amino acids join together to form a dipeptide. A ‘H’

from the amine ( NH2) group of one of the amino acids and an ‘OH’ from the other amino acid condense to form water and join the two monomers.

Polyamides cont’d:

Nylon is an example of a synthetic polymer. Nylon is special in that it is formed by two different monomers, a diacid and a diamine.

Polyesters Polyesters are synthetic fibres, such as terylene,

made as imitations of natural materials like wool and cotton.

Polyester structure consist of many monomers joined together by ester bonds.

The monomers in polyester are : diacid + dialcohol

Polysaccarides

Polysaccarides are natural polymers such as starch and cellulose. The monomers are monosaccarides e.g. fructose or glucose (simple reducing sugars)

Two glucose units join together by the elimination of water to produce a disaccaride (sucrose) and many glucose units join together to form the polysaccaride- starch.

Starch- [ O X O X O ] n

Polysaccarides

Uses of condensation Polymers Type of Polymer

Monomer Example Uses

Synthetic Polyamide

Diacid Diamine

Nylon Fibres for clothes, ropes, nets, fishing lines

Protein Amino Acids Keratin For growth and repairs of tissues, muscles, hair, nails and enzymes in living organisms

Polyester DiacidDialcohol

Terylene Fibres for clothing, boat sails and fishing lines

Polysaccarides Monosaccarides Starch Food reserves in plants, food source of animals

Hydrolysis Hydrolysis of Polymers-

The word ‘hydrolysis’ means to split up by the addition of water. Hydro- water, lysis-to break up/separate.

Polymers which undergo hydrolysis are broken up into their respective monomers when water is added.

Hydrolysis Carbohydrates and Proteins can be

hydrolysed in two ways.

1) In the body during digestion by enzymes.

2) In the lab, by boiling with dilute Hydrochloric acid or sulphuric acid.

Properties of Monomers and Polymers Polymers tend to have totally different physical and chemical

properties from their monomers.

Polymer Monomer

Chemical Properties Physical Properties

Starch Glucose Starch turns iodine blue/black.Glucose does not.Glucose forms a brick-red precipitate with Benedict’s solution. Starch has no effect on this solution

Starch is insoluble in water. Glucose is soluble in water.

Polyethene Ethene Ethene decolorises bromine in the dark whilst polyethene has no effect on bromine

Ethene is a gas at room temperature whilst polyethene is a solid.

Videos The Polymer Party –

http://www.youtube.com/watch?v=SgWgLioazSo