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PolymersLarry Scheffler
Version 1.0
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Defnitions
Polymer:a long chain molecule made
up of many small identical units.
Monomer:the smallest repeating unit of
a polymer (propene in polypropylene).
.
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IUPAC Defnition A polymer is a substance composed of
molecules characterized by the multiple
repetition of one or more species of
atoms or groups of atoms (constitutional
repeating units) lined to each other inamounts sufficient to pro!ide a set of
properties that do not !ary maredly
"ith the addition of one or a fe" of theconstitutional repeating units.#
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Common Polymers
$olymers are common in nature. %ood&
rubber& cotton& sil& proteins& enzymes&
and cellulose are all e'amples of polymers
A "ide !ariety of synthetic polymers ha!e
been produced& largely from petroleum
based ra" materials. hese include
polyurethane& teflon& polyethylene&polystyrene& and nylon.
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Common Polymers
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Polymer Recycling Codes
ommon household polymers
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Polymers
he number code indicates the polymer type
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Polymers
ypes of synthetic and natural polymers.
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Addition Polymers
Addition polymerization* a reaction in "hichunsaturated monomers combine "ith each other to forma polymer
+'ample* etrafluoroethene can be polymerized to form
polytetrafluoroethene& commonly no"n as eflon
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Addition Polymers
Some common addition polymers
,any plastics areaddition polymersmade from
hydrocarbonsources.
he hydrocarbonmust beunsaturated in orderto polymerize
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Addition Polymers
$oly!inyl chloride
$oly!inyl chloride or
$V is "ide used
for pipes and other
structural materials Vinyl chloride is also
no"n as
chloroethene
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Condensation Polymers
ondensation polymers form from
condensation reactions.
-n a condensation polymer a smaller
molecule such as "ater is eliminated
-n order to form a condensation polymer
the monomer must ha!e t"o functional
groups
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Example o a CondensationPolymer
ylon // is a condensation polymer
-t is also a copolymer since it is made from
t"o different monomers
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Example o a CondensationPolymer 2
acron is also a condensation polymer
-t is also a copolymer since it is made from t"o
different monomers
Ethylene Glycol (1,2ethanediol) para Terephthalic acid
Dacron is an example o a polyester
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Co-polymers
o polymers are made from than onemonomer
,any natural polymers are copolymers.
2or e'ample& proteins are condensationpolymers formed by 3oining as many as 40
different amino acids
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Polymer Structure
Molec!lar Mass:5 $olymers are high molecular mass structures
5 +'tremely large molecular "eights are to be found in
polymers "ith !ery long chains.
Molec!lar "hape:5 $olymer chain molecules are usually straight chains
5 hese chains may bend& coil and in& leading to
e'tensi!e intert"ining and entanglement of neighboring
chain molecules.
5 hese random coils and molecular entanglements are
responsible for many of the important characteristics of
polymers.
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!e Polymer StructureDetermines its C!aracteristics
he physical properties of a polymer& such as its strengthand fle'ibility depend on:
#hain len$th -n general& the longer the chains thestronger the polymer6
"ide $ro!ps $olar side groups gi!e stronger attractionbet"een polymer chains& maing the polymer stronger6 %ranchin$ Straight& unbranched chains can pac
together more closely than highly branched chains. hesepolymers are more crystalline and therefore stronger6
#ross&lin'in$ -f polymer chains are lined togethere'tensi!ely by co!alent bonds& the polymer is harder andmore difficult to melt.
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Structure" #inear Polymers
5Linear $olymers ha!e monomerunits that are 3oined together end toend in single fle'ible chain.
5Linear polymers ha!e e'tensi!e !ander %aals attractions bet"een thechains.
5+'amples* polyethylene& poly!inylchloride& polystyrene& and nylon
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Structure" $ranc!ed Polymers
5 7ranched $olymers ha!e side or branchchains are connected to the main ones.
5 he branches& considered to be the part
of the mainchain molecules& result fromside reactions that occur during thesynthesis of the polymer.
5 he pacing efficiency is reduced "ith
the formation of side branches& "hichresults in a lo"ering of the polymerdensity
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Structure" Cross-#in%ed Polymers
5Ad3acent linear chains are 3oined one toanother at !arious positions by co!alentbonds.
5 he process of cross lining is achie!ed eitherduring synthesis or by a nonre!ersiblechemical reaction that is usually carried out atan ele!ated temperature.
5 his cross lining is accomplished by additi!eatoms or molecules that are co!alently bonded
to the chains.5 ,any of the rubber elastic materials are cross
lined. -n case of rubbers& it is called!ulcanization
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Structure" &et'or% Polymers
5 et"or $olymers ha!e trifunctionalmonomer units&
5 8a!ing three acti!e co!alent bonds allo"
these polymers to form threedimensionalnet"ors instead of the linear chainframe"or
5 et"or polymers ha!e distincti!emechanical and thermal properties.
5 +'amples include epo'ies and otheradhesi!es.
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Polymer Properties
Stretch
Linear Polymer
The chains can be stretched, which causes
them to flow past each other. When released,the polymer will not return to its original form.
Stretch
Cross-Linked Polymer
The cross-links hold the chains together.When released, the polymer will return to it'soriginal form.
Relax
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Polymer Microstructure$olyolefins "ith side chains ha!e stereocenters on e!ery other
carbonCH3
n
CH3 CH3 CH3 CH3 CH3 CH3CH3
With so many stereocenters, the stereochemistry can be complex.
There are three main stereochemical classifications for polymers.Atactic:random orientation
Isotactic:All stereocenters have same orientation
Syndiotactic:Alternating stereochemistry
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Microstructure andProperties
acticity affects the physical properties5Atactic polymers "ill generally be amorphous& soft&
fle'ible materials5 -sotactic and syndiotactic polymers "ill be more
crystalline& thus harder and less fle'ible.
$olypropylene ($$) is a good e'ample5Atactic polypropylene is a lo" melting& gooey material
5 -soatactic polypropylene is is high melting (19/:)&crystalline& tough material that is industrially useful5 Syndiotactic polypropylene is has similar properties&
but is !ery clear. -t is harder to synthesize