N5 – Unit 3 - Chemistry in Society Polymers

Examples of plastics

Polythene [poly(ethene)] Polystyrene Perspex PVC Nylon Bakelite Formica Silicones

PVC [poly(vinyl chloride)]

Nylon

Bakelite

Formica

Silicones

Where do plastics come from? Crude oil –Fractional distillation –Cracking Alkenes

Uses related to properties Flexible Watertight Shatter-proof Light

Non-biodegradable Can’t be broken down by living things. “ Biopol ” is a recently developed biodegradable plastic.

Other problems with plastics Low density Durable Burn or smoulder to give off toxic fumes –Carbon monoxide –Hydrogen chloride –Hydrogen cyanide

Types of plastic Thermoplastic – Can be reshaped on heating Thermosetting plastic – Cannot be reshaped on heating

Chemistry of plastics Plastics are examples of polymers –These are long chain molecules made from smaller molecules joining together These smaller molecules are called monomers There are two types of polymer: –Addition polymer –Condensation polymer

Addition polymers

Like all polymers, these are made from monomers. For an addition polymer, these monomers always have a C=C These join together in a reaction called addition polymerisation. –view animationanimation

…… MONOMERSPOLYMERS ++ … …

MONOMERS POLYMERS … …

Naming polymers The name of the polymer is made by taking the name of the monomer, putting brackets around it, and adding “poly” in front –Poly(ethene) is made from ethene; –Poly(vinyl chloride) is made from vinyl chloride.

Naming practice Name the polymer made from: –Propene –Chloroethene Name the monomer used to make: –Poly(heptene) –Poly(phenylethene)

Drawing polymers, monomers and the repeating unit

C=C H C6H5C6H5 H H H C6H5C6H5 H H H C6H5C6H5 H H Poly(phenylethene)

Condensation polymers

What type of molecule is produced from an alkanol and alkanoic acid? –Esters Polyesters are made from similar molecules.

Polyesters

Monomers Must have two functional groups per molecule –For polyesters, they are a diol and a diacid

Condensation polymerisation The joining up of two molecules, producing water, is condensation. Because giant molecules are made, this is condensation polymerisation. Specifically with a diol and a diacid, a polyester is produced.

Polyamides Are produced when an amine group reacts with a carboxyl group.

Amides Formed when an amine reacts with an alkanoic acid. aminecarboxylic acid amide An AMIDE group

Polyamides Are condensation polymers. Formed when a diamine reacts with a diacid.

When condensation polymerisation takes place, the monomer molecules join to make the polymer molecule and water. Condensation polymers are made from monomers with two functional groups per molecule. Carboxyl group in acids Amino group Ester group -OH Hydroxyl group in alcohols R = the rest of the molecule

The Ester Linkage When a carboxylic acid and an alcohol react, a water molecule is removed, and an ester molecule is formed.

Polyesters Polyesters are examples of condensation polymers that contain many ester linkages.  formed from alcohols with two -OH groups, one at either end of the molecules and acids with two –COOH groups, one at either end of the molecule.

The polyester molecules can continue to grow in both directions. The acid and alcohol group join together. The acid group loses an –OH and the alcohol loses an –H to form water and a new bond forms between the monomer units.

Amines The amines belong to a homologous series based on the alkanes in which a hydrogen has been replaced with -NH 2. The functional group in the amine family is the amine or amino group ‑ NH 2.

Polyamides Polyamides are polymers formed from molecules with amine groups (-NH 2 ) and molecules with carboxyl groups (-COOH).

The carboxyl group and the amino group can join together with the loss of water. The (-CONH) link shown below is called an amide (or peptide) link and the polymer is called a polyamide.

Nylon Nylon is a polyamide that can be made from two different monomer units. One is a diacid; the other is a diamine.

Recently developed plastics Kevlar –Very strong Poly(ethenol) –Water soluble Biopol –Biodegradable

Kevlar

Poly(ethenol)