matriculation chemistry polymers.pdf

8/12/2019 Matriculation Chemistry Polymers.pdf

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FJ/Chemistry Unit, KMPk/Mac 2006 1

CHAPTER 21

POLYMERS


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21.1 : Introduction

Polymer- is a macro molecule that is made up of many small repeating units

called monomers linked together by covalent bond.

- polymer can be represented by their repeating unit in the longchain.

Monomer- is a basic molecular units that can joined to many others to form a

polymer.

n --n

polymermonomer

polymer!repeating unit"

nn ---------


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#omopolymer

- a polymer formed from only one types monomer units.

- $%ample :

n --n

ethene!ethylene"

polyethene!polyethylene"

n --n


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&opolymer

- a polymer formed from t'o or more different monomers.

- $%ample:

1(1-dichloroethene 1-chloroethene )aran*

nn + n, --,-

n &&l2+ n &l --&&l2--&l-n


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21.2 : )tructures of Polymers

21.2.1 : inear Polymers

inear polymer is a polymer consist of monomers that arelinked in straight and long continuous chain.

inear or straight-chain polymer can be folded back upon

themselves in a random fashion.inear polymer is recycleable because it is soft and can bereformed 'hen heated.

n---------monomers link togetherin a straight chain

folded linear polymer

in a random fashion


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21.2.2 : &ross-linked Polymers

&ross-linked polymer contains branches that connect linear polymer chain( as sho'n

in the figures belo'.

&ross-linked polymer is harder !rigid" and more elastic polymer compared to linearpolymer.

It also cannot be remelted or remolded again.

he e/uation belo' sho's the chemical reaction for the rubber vulcani0ation

process.

ong polymer chain cross-linked by branched

-------------

-------------

1 1


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In a vulcani0ation process( long chain of polyisoprene are cross-linked by sulphuratoms.

fter vulcani0ation rubber becomes more stable over 'ide ranges of temperature

and far more durable than natural rubber.

-& -- +

-& --

sulphur

-& --& --

)

-& --& --

)


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21. : ypes of Polymers

21..1 : 3atural Polymers

3atural polymers are polymers that synthesi0ed in natureor naturally occurring polymers.

i. ProteinsProtein are the most abundant organic molecules in animalssuch as en0ymes( hormones( hemoglobin and many otherthings.

It is a natural polymer built from amino acids linked by

amide bonds.

#3-&-&

4#

5 n


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ii. &arbohydrates

&arbohydrates such as starch is also a polymer.

i. )tarch !amylose"

ii. )tarch !amylopectin"

- contains 6-!1(7"-glycosidic and 6-!1(8"-glycosidic linkages.

4 4

4# #

44 4## #

#

##

# #

4#

4#

4#

#

#

#

n-!1(7"-glycosidic linkages


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iii. 3atural 5ubber

3atural rubber is a polymer of 2-methyl-1(-butadiena( also kno'n as

isoprene.

nother name for natural rubber is cis-1(7-polyisoprene.

ll the double bond in natural rubber are cis- configuration.

3atural rubber is soft( not strong or elastic and sticky( that makes it lessuseful.

In order to make it more useful rubber has to undergo a vulcani0ation process.

n &- --&9-

n

isoprene cis-polyisoprene


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21..2 : )ynthetic Polymers

)ynthetic polymers are polymers that are prepared in industries frommonomers that have gone through polymeri0ation process.

Polymeri0ationis a process that combines monomers to form polymers.

)ynthetic polymers can be classified base on their method of preparation! polymeri0ation process ".

21..2.1 : ddition Polymeri0ationddition polymeri0ation is the addition reaction in 'hich unsaturatedmonomers are joined together by covalent bonds to form a polymer'ithout elimination of a small molecule.

Polymers obtained by addition polymeri0ation are called addition polymers.


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herefore( addition polymer al'ays involves thepolymeri0ation of monomers 'hich have double bond'ithin

the monomers.Pero%ide is used as initiator in addition polymeri0ation.

i. ormation of polyethene

ii. ormation of polyvinyl chloride

n ---5445

! "n

n#& -#&--5445 ! "n

&l &l

ethene polyethene

chloroethene polychloroethene!polyvinyl chloride or P;&"


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iii. ormation of polystyrene

iv. ormation of polyisopropene

phenylethene!styrene"

Polyphenylethene!polystyrene"

isoprene polyisoprene

n#& -#&--5445 ! "n

n &- --&9-

n


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21..2.2 : &ondensation Polymeri0ation

&ondensation polymeri0ation is a process that combines the monomers'ith elimination of a small molecule such as 'ater( methanol( hydrogenchloride or ammonia to form a polymer.

he polymers obtained from condensation polymeri0ation are calledcondensation polymers.

he monomers involves in this polymeri0ation must have at least t'oidentical or different functional group in the molecule.


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!". Polyamides

i. ormation of 3ylon 8(8

ii. ormation of 3ylon 8

he%ane-1(8-diamine

3ylon 8(8

44

n#23-!"8-3#2 + n#4-&-!"7-&-4#

-3-!"8-3-&-!"7-&- + n#24

4 4# #

! "n

he%ane-1(8-dioic acid

! "nn#23-!">-&-4#

4 4

-3#-!">-&- + n#24

3ylon 88-aminohe%anoic


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iii. ormation of ?evlar

!,". Polyester

he repeating functional groups in this polymer chain are ester.

he most familiar polyester is polyethylene terephthalate kno'n as @acron anderylene.

1(7-diaminoben0ene

?evlar

terephthalic acid

n #-3- -3-# + n &l-&- -&-&l

4 4##

3- -3-&- -&

# # 44

n+ n #&l


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he polymer is formed by the reaction of ethylene glycol'ith methyl ester or terephtalic acid.

In this process( a molecule of methanol is split out foreach ne' ester group formed.

i. ormation of @acron

@acron orpoly!ethylene terephthalate" metanol

4 4n-&- -&-4 + n#4--4#

-4--4-&- -&- + n#

4 4! "n

1(2-ethanediol!ethylene glycol"

dimethyl terephthalate


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ii. ormation of erylene

erylene

ethane-1(2-diol ben0ene-1(7-dicarbo%ylic acid

'ater

44

n#4--4# + n #4-&- -&-4#

-4--4-&- -&- + n#24

4 4

! "n


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21.7 : Ases of )ynthetic Polymers

3o. Polymer Ases

1 Polyethene plastics( drinking bottles( toys

2 Polyvinyl chloride piping( floor tiles( clothing( toys(

'ire covering Polystyrene containers( thermal insulation-ice buckets

7 3ylon 8 e%tile

> 3ylon 8(8 )'eater

8 ?evlar ,ullet proof vestB @acron abric

C erylene iber-optic material

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