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Conducting Polymers
Master in Nanoscience
Low dimensional system and nanostructures
January 2009
Yasmin Khairy Abd l !atah
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"#$L%N
%ntroduction
&hat is conducti'ity(
&hat ma)es amaterial conducti'e(
*ow can +lastic become conducti'e(
,o+ing +rocess-
.actors that a!!ect the conducti'ity-
A++lications-Conclusion-
/ibliogra+hy search-
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%ntroduction
Polymers or +lastics as they are also called1 are
)nown to ha'e good insulating +ro+erties-
Polymers are one o! the most used materials in the modernworld- $heir uses and a++lication range !rom containers to
clothing-$hey are used to coat metal wires to +re'ent electric shoc)s-
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Yet Alan J- *eeger Alan 3- Mac,iarmid and *ide)i 4hira)awa ha'e
changed this 'iew with their disco'ery that a +olymer +olyacetylene
can be made conducti'e almost li)e a metal-
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What is conductivity?
Conducti'ity can be de!ined sim+ly by "hms Law-
56 %7&here 7 is the resistance % the current and 5 the'oltage+resent in
the material- $he conducti'ity de+ends on the number o! chargecarriers number o! electrons1 in the material and their mobility-%n ametal it is assumed that all the outer electrons are !ree to carrycharge and the im+edance to !low o! charge is mainly due to theelectrons 8bum+ing8 in to each other-
%nsulators howe'er ha'e tightly bound electrons so that nearly no
electron !low occurs so they o!!er high resistance to charge !low-
4o !or conductance !ree electrons are needed-
http://www.chm.bris.ac.uk/webprojects2001/parrott/pages/resistance.htmhttp://www.chm.bris.ac.uk/webprojects2001/parrott/pages/voltage.htmhttp://www.chm.bris.ac.uk/webprojects2001/parrott/pages/voltage.htmhttp://www.chm.bris.ac.uk/webprojects2001/parrott/pages/resistance.htm7/25/2019 Conducting Polymers 4
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&hat ma)es the material conducti'e(
$hree sim+le carbon com+ounds are diamond gra+hite and+olyacetylene- $hey may be regarded as three two and onedimensional !orms o! carbon materials -
,iamond which contains only : bonds is an insulator
and its high symmetry gi'es it isotro+ic +ro+erties-
3ra+hite and acetylene both ha'e mobile ; electrons
and are when do+ed highly anisotro+ic metallic
conductors-
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*ow can +lastic become conducti'e(
Plastics arepolymers molecules that !orm long chains re+eating
themsel'es- %n becoming electrically conducti'e a +olymer has to
imitate a metal that is its electrons need to be !ree to mo'e and
not bound to the atoms- Polyacetyleneis the sim+lest +ossible
con
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$wo conditions to become
conducti'e=
>$he !irst condition !or this is that the +olymer consists o! alternating
single and double bonds called con
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2$he second condition is that the +lastic has to be disturbed either by remo'ing electrons !rom oidation1 or insertingthem into reduction1 the material- $he +rocess is )nown as
Doping.$here are two ty+es o! do+ing=
>oidation with halogen orp-do+ing1-
2 7eduction with al)ali metal called ndo+ing1-
( ) ( ) + ++ xNaCHxNaCH xnn
( ) ( ) + ++3
2
3ICHI
xCH
nn
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$he game o!!ers a sim+le model o! a do+ed +olymer- $he +iecescannot mo'e unless there is at least one em+ty 8hole8- %n the+olymer each +iece is an electron that
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,o+ing +rocess
$he halogen do+ing trans!orms +olyacetylene to a good conductor-
"idation with iodine causes the electrons to be
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$he iodine molecule attracts an electron !rom the
+olyacetylene chain and becomes %B- $he +olyacetylene
molecule now +ositi'ely charged is termed a radical cationorpolaron.
D $he lonely electron o! the double bond !rom which an
electron was remo'ed can mo'e easily- As aconseEuence the double bond successi'ely mo'es along
the molecule-D $he +ositi'e charge on the other hand is !ied by
electrostatic attraction to the iodide ion which does not
mo'e so readily-
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,"P%N3 ."7 /$$7
M"LC#L P7."7MANC
Doped polyacetylene is, e.g., comparable to good conductors
such as copper and silver, whereas in its original form it is a
semiconductor.
Conductivity of conductive polymers compared to those of other
materials, from quartz (insulator to copper (conductor. !olymers
may also have conductivities corresponding to those of
semiconductors.
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.actors that a!!ect the conducti'ity
>,enesity o! charge carriers-
2 $hier mobility-
B$he direction-F+resence o! do+ing materials
additi'es that !acilitate the +olymer
conducti'ity1G$em+erature-
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The conductivity of conductive polymers decreases with falling
temperature in contrast to the conductivities
of typical metals, e.g. silver, which increase with fallingtemperature.
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A++lications
Conducting +olymers ha'e many uses- $he most documented
are as !ollows=antistatic substances !or +hotogra+hic !ilm
Corrosion %nhibitors
Com+act Ca+acitors
Anti 4tatic Coating
lectromagnetic shielding !or com+uters84mart &indows8
A second generation o! conducting +olymers ha'e beende'elo+ed these ha'e industrial uses li)e=
$ransistors
Light mitting ,iodes L,s1
Lasers used in !lat tele'isions4olar cells
,isplays in mobile telephones and mini"formattelevision screens
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Photogra+hic .ilm
smart8 windows
4hield !or com+uter screen
against electromagnetic
8smart8 windows
radiation
Lightemitting diodes
4olar cell
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Conclusion
.or conductance !ree electrons are needed-
Con
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/ibliogra+hic 4earch
#. $hira%awa, &.'. ouis, ).*. +acDiarmid, C.. Chiang and ).'.
#eeger, ' Chem $oc Chem Comm (-// 0/
1. 2to, #. $hira%awa and $. 2%eda, '.!olym.$ci.,!olym.Chem. &d. -3
(-/4 --536
C.. Chiang, C.7. 8ischer, 9.W. !ar%, ).'. #eeger, #. $hira%awa, &.'.
ouis, $.C. *au and ).*. +acDiarmid , !hys. 7ev. etters : (-//
-6;C.. Chiang, +.). Druy, $.C. *au, ).'. #eeger, &.'. ouis, ).*.
+acDiarmid
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