1. A guide for A level students KNOCKHARDY PUBLISHING
THE CHEMISTRY
OF POLYMERS
A guide for A level students
KNOCKHARDY PUBLISHING

2. KNOCKHARDY PUBLISHING
POLYMERS
INTRODUCTION
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3. POLYMERS CONTENTS Prior knowledge Types of polymerisation
Addition polymerisation
Polymerisation of propene
Condensation polymerisation
Peptides
Check list

4. Before you start it would be helpful to…
POLYMERS
Before you start it would be helpful to…
know the functional groups found in organic chemistry
know the arrangement of bonds around carbon atoms
recall and explain electrophilic addition reactions of alkenes

5. There are two basic types
POLYMERISATION
General A process in which small molecules called monomers join
together into large molecules consisting of repeating units.
There are two basic types
ADDITION all the atoms in the monomer are used to form the polymer
CONDENSATION monomers join up the with expulsion of small molecules
not all the original atoms are present in the polymer

6. ADDITION POLYMERISATION
• all the atoms in the monomer are used to form the polymer
• occurs with alkenes
• mechanism can be free radical or ionic

7. POLYMERISATION OF ALKENES ADDITION POLYMERISATION
Preparation
Many are prepared by a free radical process involving high pressure, high temperature and a catalyst. The catalyst is usually a substance (e.g. an organic peroxide) which readily breaks up to form radicals whichinitiate a chain reaction.
Another famous type of catalyst is a Ziegler-Natta catalyst (named after the scientists who developed it). Such catalysts are based on the compound TiCl4.
Properties
Physical varied by changing the reaction conditions (pressure, temperature etc).
Chemical have chemical properties based on the functional groups in their structure.
poly(ethene) is typical; it is fairly inert as it is basically a very large alkane.
This means it is resistant to chemical attack and non-biodegradable.

8. POLYMERISATION OF ALKENES ADDITION POLYMERISATION
Process • during polymerisation, an alkene undergoes an addition reaction with itself
• all the atoms in the original alkenes are used to form the polymer
• long hydrocarbon chains are formed
the equation shows the original monomer and the repeating unit in the polymer
ethene poly(ethene)
MONOMER POLYMER
n represents a large number

9. POLYMERISATION OF ALKENES ADDITION POLYMERISATION
the equation shows the original monomer and the repeating unit in the polymer
ethene poly(ethene)
MONOMER POLYMER
n represents a large number

10. POLYMERISATION OF ALKENES EXAMPLES OF ADDITION POLYMERISATION
ETHENE
POLY(ETHENE)
PROPENE
POLY(PROPENE)
CHLOROETHENE
POLY(CHLOROETHENE)
POLYVINYLCHLORIDE PVC
TETRAFLUOROETHENE
POLY(TETRAFLUOROETHENE)
PTFE “Teflon”

11. POLYMERISATION OF ALKENES
SPOTTING THE MONOMER

12. POLYMERISATION OF ALKENES
SPOTTING THE MONOMER

13. POLYMERISATION OF PROPENE - ANIMATION
AN EXAMPLE OF ADDITION POLYMERISATION
PROPENE MOLECULES DO NOT ALWAYS ADD IN A REGULAR WAY
THERE ARE THREE BASIC MODES OF ADDITION
ISOTACTIC
SYNDIOTACTIC
ATACTIC
Animation may not work in earlier versions of Powerpoint

14. POLY(PROPENE) ISOTACTIC SYNDIOTACTIC ATACTIC CH3 groups on same side
- most desirable properties
- highest melting point
SYNDIOTACTIC
CH3 groups alternate sided
ATACTIC
random
most likely outcome

15. CONDENSATION POLYMERS
• monomers join up the with expulsion of small molecules
• not all the original atoms are present in the polymer
Examples polyamides (nylon)
polyesters (terylene)
peptides
starch
Synthesis reactions between diprotic carboxylic acids and diols
diprotic carboxylic acids and diamines
amino acids
ESTER LINK
AMIDE LINK

16. POLYESTERS - TERYLENE Reagents terephthalic acid HOOC-C6H4-COOH
ethane-1,2-diol HOCH2CH2OH
Equation n HOCH2CH2OH + n HOOC-C6H4-COOH ——> -[OCH2CH2OOC(C6H4)CO] n n H2O
Product poly(ethylene terephthalate) ‘Terylene’, ‘Dacron’
Repeat unit — [-OCH2CH2OOC(C6H4)CO-] n —
Eliminated water
Reaction esterification
Properties contain an ester link
can be broken down by hydrolysis
the C-O bond breaks
behaves as an ester
biodegradable
Uses fabrics

17. POLYAMIDES - NYLON-6,6 Reagents hexanedioic acid HOOC(CH2)4COOH
hexane-1,6-diamine H2N(CH2)6NH2
Equation n HOOC(CH2)4COOH + n H2N(CH2)6NH2 ——> -[NH(CH2)6NHOC(CH2)4CO] n- + n H2O
Product Nylon-6,6 two repeating units, each with 6 carbon atoms
Repeat unit —[-NH(CH2)6NHOC(CH2)4CO-]n—
Eliminated water
Mechanism addition-elimination
Properties contain a peptide (or amide) link
can be broken down by hydrolysis
the C-N bond breaks
behave as amides
biodegradable
can be spun into fibres for strength
Uses fibres and ropes

18. Amino acids join together via an amide or peptide link
PEPTIDES
Reagents amino acids
Equation H2NCCH2COOH H2NC(CH3)COOH ——> H2NCCH2CONHHC(CH3)COOH + H2O
Product peptide (the above shows the formation of a dipeptide)
Eliminated water
Mechanism addition-elimination
Amino acids join together via an amide or peptide link
2 amino acids joined dipeptide
3 amino acids joined tripeptide
many amino acids joined polypeptide
a dipeptide

19. PROTEINS
• polypeptides with large relative molecular masses (>10000)
• chains can be lined up with each other
• the C=O and N-H bonds are polar due to a difference in electronegativity
• hydrogen bonding exists between chains
dotted lines represent hydrogen bonding

20. What should you be able to do?
REVISION CHECK
What should you be able to do?
Recall the two main types of polymerisation
Explain and understand how alkenes undergo addition polymerisation
Work out the repeating unit in addition polymers
Recall and understand the different types of structures of poly(propene)
Recall the properties of some common polymers
Recall that polyesters and polyamides are formed by condensation polymerisation
Recall the properties and uses of some condensation polymers
Work out the repeating unit in condensation polymers
Recall that peptides are examples of condensation polymers
CAN YOU DO ALL OF THESE? YES NO

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22. Try some past paper questions
WELL DONE!
Try some past paper questions

23. © 2003 JONATHAN HOPTON & KNOCKHARDY PUBLISHING
THE CHEMISTRY
OF POLYMERS
THE END
© 2003 JONATHAN HOPTON & KNOCKHARDY PUBLISHING