(h) Synthetic polymers

4:45 understand how to draw the repeat unit of an addition polymer, including poly(ethene), poly(propene), poly(chloroethene) and (poly)tetrafluroethene

                              

 

 

                              

 

 

                              

 

 

                              

4:46 understand how to deduce the structure of a monomer from the repeat unit of an addition polymer and vice versa

To deduce the structure of the monomer from a repeat unit:

  1. Remove the extending single bonds
  2. Draw in a double bond

 

 

 

Here’s a more complicated example, going from the polymer to the structure of the monomer

4:48 (Triple only) know that condensation polymerisation, in which a dicarboxylic acid reacts with a diol, produces a polyester and water

Condensation polymers are formed by a condensation reaction.

These polymers are formed by the combination of two different monomers, such as a dicarboxylic acid and a diol.

When these particular monomers join in an alternating pattern they form a long polymer called a polyester. Where each monomer joins to the next, a separate molecule of water is also produced.

 

 

4:49 (Triple only) Understand how to write the structural and displayed formula of a polyester, showing the repeat unit, given the formulae of the monomers from which it is formed, including the reaction of ethanedioic acid and ethanediol:

Polyesters are polymers formed when two types of monomer join together alternately. Where each joins to the next a small molecule, such as water or hydrogen chloride, is lost. This is called a condensation polymerisation reaction.

 

One of the monomers is a diol, an alcohol with a -OH functional group at each end. An example is hexane-1,6-diol which has the structural formula CH₂OHCH₂CH₂CH₂CH₂CH₂OH and the displayed formula:

Since it is only the -OH functional groups which are important for polymerisation, this can we re-written with the central block of carbons represented as a block:

 

The other monomer is a dicarboxylic acid, a molecule with a -COOH functional group at each end. An example is hexane-1,6-dioic acid which has the structural formula HOOCCH₂CH₂CH₂CH₂COOH and the displayed formula:

Since it is only the -COOH functional groups which are important for polymerisation, this can we re-written with the central block of 4 carbons represented as a block:

 

These two different types of monomer (the diol and the dicarboxylic acid) can join to form a polymer with the loss of a water molecule at every bond. As above, this can be simplified by only looking at the functional groups and representing the other carbons as blocks, so the whole process looks like:

 

A simple example of this is the condensation polymerisation reaction between ethanedioic acid and ethandiol:

4:50 (Triple only) know that some polyesters, known as biopolyesters, are biodegradable

There are environmental issues with the disposal of condensation polymers, though because of their ester linkage the issues are not as severe as with addition polymers. Normally condensation polymers can take hundreds of years to break down, but chemists has developed biopolyesters which break down much more quickly.

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Section 1: Principles of chemistry

      a) States of matter

      b) Atoms

      c) Atomic structure

     d) Relative formula masses and molar volumes of gases

     e) Chemical formulae and chemical equations

     f) Ionic compounds

     g) Covalent substances

     h) Metallic crystals

     i) Electrolysis

 Section 2: Chemistry of the elements

     a) The Periodic Table

     b) Group 1 elements: lithium, sodium and potassium

     c) Group 7 elements: chlorine, bromine and iodine

     d) Oxygen and oxides

     e) Hydrogen and water

     f) Reactivity series

     g) Tests for ions and gases

Section 3: Organic chemistry

     a) Introduction

     b) Alkanes

     c) Alkenes

     d) Ethanol

Section 4: Physical chemistry

     a) Acids, alkalis and salts

     b) Energetics

     c) Rates of reaction

     d) Equilibria

Section 5: Chemistry in industry

     a) Extraction and uses of metals

     b) Crude oil

     c) Synthetic polymers

     d) The industrial manufacture of chemicals