the chemistry of polymers

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

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The Chemistry Of Polymers

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Page 1: The Chemistry Of Polymers

THE CHEMISTRYTHE CHEMISTRYOF POLYMERSOF POLYMERS

A guide for A level studentsA guide for A level students

KNOCKHARDY PUBLISHINGKNOCKHARDY PUBLISHING

Page 2: The Chemistry Of Polymers

INTRODUCTION

This Powerpoint show is one of several produced to help students understand selected topics at AS and A2 level Chemistry. It is based on the requirements of the AQA and OCR specifications but is suitable for other examination boards.

Individual students may use the material at home for revision purposes or it may be used for classroom teaching if an interactive white board is available.

Accompanying notes on this, and the full range of AS and A2 topics, are available from the KNOCKHARDY SCIENCE WEBSITE at...

www.knockhardy.org.uk/sci.htm

Navigation is achieved by...

either clicking on the grey arrows at the foot of each page

or using the left and right arrow keys on the keyboard

POLYMERSPOLYMERSKNOCKHARDY PUBLISHINGKNOCKHARDY PUBLISHING

Page 3: The Chemistry Of Polymers

CONTENTS

• Prior knowledge

• Types of polymerisation

• Addition polymerisation

• Polymerisation of propene

• Condensation polymerisation

• Peptides

• Check list

POLYMERSPOLYMERS

Page 4: The Chemistry Of 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

POLYMERSPOLYMERS

Page 5: The Chemistry Of Polymers

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

POLYMERISATIONPOLYMERISATION

Page 6: The Chemistry Of Polymers

• all the atoms in the monomer are used to form the polymer

• occurs with alkenes

• mechanism can be free radical or ionic

ADDITION POLYMERISATIONADDITION POLYMERISATION

Page 7: The Chemistry Of Polymers

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.

POLYMERISATION OF ALKENESPOLYMERISATION OF ALKENES

ADDITION POLYMERISATION

Page 8: The Chemistry Of Polymers

POLYMERISATION OF ALKENESPOLYMERISATION OF ALKENES

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

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

Page 9: The Chemistry Of Polymers

POLYMERISATION OF ALKENESPOLYMERISATION 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

Page 10: The Chemistry Of Polymers

POLYMERISATION OF ALKENESPOLYMERISATION OF ALKENES

ETHENE

EXAMPLES OF ADDITION POLYMERISATION

PROPENE

TETRAFLUOROETHENE

CHLOROETHENE

POLY(ETHENE)

POLY(PROPENE)

POLY(CHLOROETHENE)

POLYVINYLCHLORIDE PVC

POLY(TETRAFLUOROETHENE)

PTFE “Teflon”

Page 11: The Chemistry Of Polymers

POLYMERISATION OF ALKENESPOLYMERISATION OF ALKENES

SPOTTING THE MONOMER

Page 12: The Chemistry Of Polymers

POLYMERISATION OF ALKENESPOLYMERISATION OF ALKENES

SPOTTING THE MONOMER

Page 13: The Chemistry Of Polymers

POLYMERISATION OF PROPENE - ANIMATIONPOLYMERISATION OF PROPENE - ANIMATION

AN EXAMPLE OF ADDITION POLYMERISATION

ISOTACTICSYNDIOTACTICATACTIC

PROPENE MOLECULES DO NOT ALWAYS ADD IN A REGULAR WAY

Animation may not work in earlier versions of Powerpoint

THERE ARE THREE BASIC MODES OF ADDITION

Page 14: The Chemistry Of Polymers

POLY(PROPENE)POLY(PROPENE)

ISOTACTICCH3 groups on same side

- most desirable properties- highest melting point

SYNDIOTACTICCH3 groups alternate sided

ATACTICrandommost likely outcome

Page 15: The Chemistry Of Polymers

CONDENSATION POLYMERSCONDENSATION 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)peptidesstarch

Synthesis reactions between diprotic carboxylic acids and diols diprotic carboxylic acids and diamines amino acids

ESTER LINK AMIDE LINK

Page 16: The Chemistry Of Polymers

POLYESTERS - POLYESTERS - TERYLENETERYLENE

Reagents terephthalic acid HOOC-C6H4-COOHethane-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

Page 17: The Chemistry Of Polymers

POLYAMIDES - POLYAMIDES - NYLON-6,6NYLON-6,6

Reagents hexanedioic acid HOOC(CH2)4COOHhexane-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-6,6two 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

Page 18: The Chemistry Of Polymers

PEPTIDESPEPTIDES

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

Page 19: The Chemistry Of Polymers

PROTEINSPROTEINS

• 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

Page 20: The Chemistry Of Polymers

REVISION CHECKREVISION 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? CAN YOU DO ALL OF THESE? YES YES NONO

Page 21: The Chemistry Of Polymers

You need to go over the You need to go over the relevant topic(s) againrelevant topic(s) again

Click on the button toClick on the button toreturn to the menureturn to the menu

Page 22: The Chemistry Of Polymers

WELL DONE!WELL DONE!Try some past paper questionsTry some past paper questions

Page 23: The Chemistry Of Polymers

THE CHEMISTRYTHE CHEMISTRYOF POLYMERSOF POLYMERS

THE ENDTHE END

© 2003 JONATHAN HOPTON & KNOCKHARDY PUBLISHING© 2003 JONATHAN HOPTON & KNOCKHARDY PUBLISHING