1. Polymers

2.  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 reactions o Draw diagrams to represent the formulae of monomers o State at least one use of each of the following types of polymers : (i) polyalkene (ii) polyamide (iii) polyester (iv) polysaccharide o 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.

4.  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.

5.  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.

6.  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.

7.  To name a polymer, the prefix ‘Poly’ is placed before the name of the monomer.  For example: Polypropene Polystyrene Polyethene

8.  Polyalkenes have properties of substances commonly named PLASTICS. Plastics are synthetic polymers. Name of PolymerUses PolythenePackaging, plastic bags, plastic wraps. PolyvinylchlorideRaincoats, plumbing fittings, water pipes, insulation of electric wires. PolypropenePlastic containers, food containers, coolers. TeflonNon-stick coatings for irons and pots. PerspexGlass substitute in aircraft windows, reflectors on vehicles and sign boards.

10.  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 NH 3 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.

11.  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

12.  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

13.  Polyamides  Polyesters  Polysaccharides

14.  Protein is a natural polyamide. The monomers which make up proteins are amino acids.

15.  Two amino acids join together to form a dipeptide. A ‘H’ from the amine ( NH 2 ) group of one of the amino acids and an ‘OH’ from the other amino acid condense to form water and join the two monomers.

16.  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.

17.  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

18.  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

20. Type of PolymerMonomerExampleUses Synthetic Polyamide Diacid Diamine NylonFibres for clothes, ropes, nets, fishing lines ProteinAmino AcidsKeratinFor growth and repairs of tissues, muscles, hair, nails and enzymes in living organisms PolyesterDiacid Dialcohol TeryleneFibres for clothing, boat sails and fishing lines PolysaccaridesMonosaccaridesStarchFood reserves in plants, food source of animals

21.  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.

22.  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.

23.  Polymers tend to have totally different physical and chemical properties from their monomers. PolymerMonomerChemical PropertiesPhysical Properties StarchGlucoseStarch 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. PolyetheneEtheneEthene decolorises bromine in the dark whilst polyethene has no effect on bromine Ethene is a gas at room temperature whilst polyethene is a solid.

24.  The Polymer Party –  http://www.youtube.com/watch?v=SgW gLioazSo