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PolymersPolymers A large molecule consisting of repeating smaller structural units (called monmrt units)

Polymerization The sequence of repetitive reactions between a monomer unit and the growing

macromolecule or polymer chain

ie. C!"C

!# # # # $%C

!%C

!%&

n

a monomer unit polymerization polymer  

Categories of polymers' by tructural in*ing of +onomer ,nits

omopolymer -nly one type of monomer molecule is used to ma*e a polymer' with repeating units of

this one monomer 

Copolymer Polymer formed by the combination of ! or more different monomer molecules The

sequence arrangement of these units can vary in four different ways.

/) 0andom copolymer random sequence of different monomer units (A and 1)

%A%A%1%1%1%A%1%1%

!) Alternating copolymer alternating sequence of monomer units

%A%1%A%1%A%1%A%1%

2) 1loc* copolymer a sequence where there are repeating bloc*s of identical monomer units.

%A%A%A%A%1%1%1%1%A%A%A%A%1%1%1%1%

3) 4raft copolymer a chain which have side%chains from which to create e5tensions to

another polymer chain.CH2 CH CH2 CH

n

 polystyrene chain

side-chain extension

reaction

CH2 CH CH2 CH

n

O OCH3O OCH3

The ester cou ld further be functionalized

 by nucleophilic additon to the carbonyl

and expulsionof -OCH3

 groups

-perhaps by a polyamide chain

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Polymers are commonly named according to the chemical structure of the

monomer unit' and then the prefi5 poly is added.

CH2 CH

Cl

n

CH2 CH

CN

n

C

O

HO C

O

OH

C

O

C

O

O CH2 CH2 On

 plastic pop bottles

clothing

fibres poly(ethylene terephthalate)

(PT

terephthalic acid

used to ma!e a co-polymer

"ith P##$

(polymethylmethacrylate) inacrylic fibres for clothing poly(acrylonitrile)Orlon% $crilan

acrylonitrile

CH&'CH-C≡ 

emulsifying and thic!ening

agent

(non edible) in shampoos%

lubricant oils% antifreeze

 poly(ethyleneglycol)

(P)

(-CH&CH

&-O)-

ethylene glycol

HO-CH&CH

&-OH

inert% non-stic!caoting

used in carpets to ma!e

them stain resistant

-*-C+&C+

&-,

n-

 poly(tetrafluoroethylene)

(Teflon)

tetrafluoroethylene

C+&'C+

&

 plastic fittings and ales

tubing poly(inyl chloride)

(P.C)

inyl chloride

CH&'CH-Cl

 plastic bags% film

 nearly eerything

-*-CH&CH

&-,

n-

 polyethylene

ethylene

CH&'CH&

Commercial /sePolymer #onomer 

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Physical properties

The structure of the monomer will confer unique structural and physical characteristics

in the polymer at different temperatures.ome polymer chains can pac* or arrange6order themselves in a highly organized

manner' resulting in highly crystalline material. 7or e5ample linear polyethylene

 

ome polymer chains have branching on the chain and cannot order themselves in a

crystalline lattice and often said to be amorphous solids. 7or e5ample rubber

(polyisoprene)

+ost polymers are semi%crystalline' where some regions are highly ordered and

crystalline' while other regions are not and have amorphous properties.8ntermolecular forces that increase the melting point of a polymer are9

a) structural regularity in polymer chain

b) bond rigidity

c) close%pac*ing ability

d) strong inter%chain attractive forces (eg. %bonding)

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Polymer 0-oup Physical Poperty

C

O

C

O

O R On  

a terephthalate-based

 poyester

CH2 CH2  

solid

#elting point &123C

CH2 CH

CH3  not crystalline

CH2 CH CH2

CH3  not crystalline

CH2 C

CH3

CH3

CH2

 

solid

#elting point 4563C

C

O

C

O

O R On

H3C

CH3  CH2 CH2  

solid

#elting point 4763C

C

O

C

O

O R On

CH3  

CH2 CH2  

solid

#elting point 763C

CH2 CHn

C O

O

CH3   poly(methacrylate)

soft and rubbery

CH2 Cn

C O

O

CH3

CH3

  poly(methyl

methacrylate)

hard plastic

#elting point &663C

CH2 CHn

C O

OH   poly(acrylic acid)

solid

absorbs "ater

used in diapers

CH2 CHn

C O

NH2   polyacrylamide

soft plastic

used in ma!ing

soft contact lenses

:5amples

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Polymers

7ree radical Polymerization8nitiation  -usually by homolysis of an initiator molecule for example benzoyl peroxide.

 

P h  O 

O 

P h O 

O 

P h  O 

O 

P h  C O 2 2 

 homolysis 

heat 

β -bond clea!a"e 

Radical chain polymerization initiatin" species 

#enzoyl peroxide 

 phenyl -- Ph

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0adical Polymerization of vinyl +onomers9 

7or e5ample styrene.

Propagation steps9

CHH2C

8tyrene

$n

%here &$n& is formedby homolysis of a suitableinitiator moleculee.". &$n& ' Ph from decompositionof benozyl peroxide

H2C Ph$n

Ph

benzylic radical

$n

Ph

H2C Ph

$n

Ph Ph

H2C Phetc.

Ph

n

polystyrene

styrene

Note( the polymer is not homo"eneous)ith respect to molecular )ei"ht.  i.e. a mixture of polymers

)ith different number of units  in each chain is formed

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Chain termination9

In

Ph   Ph

n

In

PhPh

n

In

Ph   Ph

n

In

PhPh

n

0adical combination9

%atom transfer 9n

Ph Ph

H

Ph

HH

Ph

9n

n

n

PhPh

9n

H nn

9n

Ph Ph

HH :

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Chain transfer to polymer 

R

$nR R

$n

R R

H

H

R

R

R

R

R

H H

n

n

n

terminated polymer chain ne) radical site alon" a polymer moleculechain

n

m

#ranched chain

polymer formation

n

m

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8ntramolecular %Atom Transfer 

CH2 C

H2 C

CH2

CH2

CH2

H

H

"ro)in" chain of polyethy lene

CH2 C

H2 C

CH2

CH2

CH3H

ne) site f or polymer chain extension

CH2'CH2

CH2 CH

H2 C

CH2

H2C

CH3

CH2 CH2

n

*-carbonbranch

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+his process occurs fre,uently durin" free radical polymerization of polyethylene

#ranchin" pre!ents close-pacin" of the polymer chains and lo)ers the density of

the polymer called lo)-density polyethylene/

Hi"h density poly ethylene0 formed by other methods0 has little branchin" and has

substantial re"ions of crystallinity resultin" from close-pacin" of the polymer chains

Hi"h 1ensity Polyethylene o) 1ensity P

%hat effect does branchin" ha!e on the physical properties of a polymer pacin"0 density and meltin" point/

#ranchin" causes a decrease in meltin" point0 decreases density and maes the material more amorphous.

#ranchin" causes a decrease in the intermolecular forces bet)een the molecules. or example !e"etable oils

are unsaturated and contain cis double bonds. +he double bonds do not allo) the molecules to pac )ell

to"ether and thus the intermolecular forces bet)een the molecules are )ea. +o mae mar"arine !e"etable

oil is hydro"enated hydro"en is added to the double bonds/ to mae saturated fatty acids. 4ince the

molecules pac better to"ether the oil becomes a solid. +he oil is only partially hydro"enated because if the

oil becomes completely saturated it becomes hard and brittle. One problem )ith partial hydro"enation0 is thatthe catalyst isomerizes some of the unreacted cis double bonds to the unnatural trans arran"ement0 and there

is accumulatin" e!idence that 5trans6 fats are associated )ith an increased ris of cardio!ascular disease.

re,uent chain terminations by this mechanism decrease the a!era"e molecular )ei"ht of the polymer

obtained in this )ay

or some monomers e.". propylene/ this process occurs so fre,uently that polymers of useful chain len"th

cannot be made by free radical polymerization

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4ome !inyl polymers

H&C C+

&

inylidine fluoride

used in piezoelectric materialaudio spea!ers and microphones

styrene

used in plastics% stryofoamand isolation

 

5-inylpyridine

ion exchange resins

O

O

methyl methacrylate

 plastics% plexiglas

O

O

t -;OC styrene

 photoresists for microelectronics

O

HO

acrylic acid

thic!eners adhesiessporting goods

O

O

CH&

CH&

OH

hydroxy ethyl methacrylate(H#$)

soft contactlenses

O

O (CH&)1

O C

cyano-biphenyl mesogenic monomer 

side chain li

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8nterpenetrating polymer 

+here are many compounds that ha!e been de!eloped containin" more than

one polymerizable !inyl "roup. 8s you can expect )ith t)o reacti!e sites on onemonomer at some point crosslinin" )ill occur. $nterpenetratin" polymer

net)ors or $PNs are combinations of t)o or more polymers in net)or form. 8t

least one of the polymers is synthesized and9or crosslined in the presence of

another. 8s such0 $PNs share some of the ad!anta"es of both polymer blends

and net)or polymers. One of the earliest commercial $PNs used in the

automoti!e industry consists of polypropylene and ethylene-propylene-dieneterpolymer :P1;/. Potential applications include tou"hened plastics0 ion-

exchan"e resins0 pressure sensiti!e adhesi!es0 soft contact lenses0 preparation

of no!el membrane systems and sound- and !ibration-dampin" material.

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:

CH CH&

CH CH&

CH CH&

: heat

$9;

P$ net"or! styrene diinylbenzene P$-P8 9P

CH CH&C O

OCH&CH

3

:CH CH&C O

OCH&CH

3

O(CH&CH&OCH&CH&O )&

ethyl acrylate tetraethylene glycol dimethacrylate

$9;

heat

P$ net"or! 

 

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HC CH2

CH CH2

CH CH2

9n

CH

Ph

CH2CH

Ph

CH2

CH

Ph

CH2CH

Ph

CH2

HC CH2 $n

C

Ph

CH2 CH

Ph

CH2CH

Ph

CH2CH2 CH2

CHCH2

C

Ph

CH2 CH

Ph

CH2CH

Ph

CH2CH CH2

CHCH2HC

Ph

CH2 CH

Ph

CH2CH

Ph

CH2

HCPh

CH2 CHPh

CH2CHPh

CH2n

n

n

n

n

n

Cross linin"( 

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Catalysts for Cationic Polymerization

e.g. boron trifluoride

 

  # 

 

 

  O H 

H 

e)is acid electron deficient/ 

e)is base electron rich/ 

  # 

 

 

O 

H 

H 

this complex can no) act asa protic acidi.e. proton donor/ 

#

O

H

H

H2C

CH3

CH3

#

O

H

H3C

CH3

CH3

$nitiation

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H3C

CH3

CH3

H2C

CH3

CH3

H3C

H3C

H3C

CH2

CH3

CH3

H2C

CH3

CH3

etc.

Propa"ation

Chain Termination

CH2

CH3

CH3

CH2

CH3

CH3

FB

F

F

O

H

+CH2

CH3

CH3

CH2

CH2

CH3

FB

F

F

O

H

H

+

terminated chain

Proton transfer to catalyst

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H2C

CH3

CH3

CH2

CH3

CH3

CH2

CH3

CH3

CH2

CH3

CH3

CH2

CH2

CH3

H3C

CH3

CH3

terminated chain

Chain transfer to monomer 

Chain transfer to monomer results in short polymer chains approx. molecular )ei"ht ' 20=== -3===/ )hen the

polymerization is carried out at room temperature

4uch polymers find some use as additi!es to lubricatin" oils but are not useful as plastics or rubber 

;uch lon"er chain polymers can be produced by usin" lo) temperature ->=o C/.

-the acti!ation ener"y for chain transfer to monomer reactions is hi"her than that for chain propa"ation?

therefore0 lo)erin" the temperature slo)s do)n the chain terminatin" step more so than the propa"ation step

+hese lon"er chain polymers are still too soft and pliable for use as rubber because the polymer chains mo!e

fairly easily relati!e to one another 

+he polymers can be made tou"her and more ri"id by decreasin" the ability of polymer chains to mo!erelati!e to one another by formin" co!alent bond bet)een polymer chains

+he polymer chain crosslinin" of rubber is called !ulcanization. $n order to create polymer crosslins0

potentially reacti!e sites for co!alent bond formation ha!e to be introduced alon" the polymer chain. +his is

done by addin" a small amount approx. @- AB/ of a second monomer often isoprene/ )hen polymerization

is carried out. +he resultant co-polymer has !inyl alene/ "roups at some positions alon" the polymer chains

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$n older !ulcanization processes0 the co-polymer )as simply heated

)ith elemental sulfur to form sulfide or poly sulfide crosslins0

ho)e!er this reaction is usually !ery slo).

Current !ulcanization processes use so-called !ulcanization

accelerators

+he mechanism of the acceleration process is not )ell understood

 8 reasonable speculation is that the accelerator may react )ith elemental

sulfur faster than does the copolymer to form a reacti!e sulfur containin"

species )hich is soluble in the polymer and )hich then carries out thecrosslinin"

ree radical addition of sulfur radicals the !inyl side chains of the co-

polymer is probably in!ol!ed.

4

N4H

mercaptobenzothiazole;#+/

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C H2

CH3

CH3

C H2

CH3

CH3

CH3

H2

C

C H2

CH3

CH3

n

C H2

CH3

CH3

C H2

CH3

CH3

CH3

H2

C

C H2

CH3

CH3

m

4

heat

C H2

CH3

CH3

C H2

CH3

CH3

CH3

CH2

H2

C

C H2

CH3

CH3

n

C H2

CH3

CH3

C H2

CH3

CH 3

CH3

CH2

H2

C

C H2

CH3

CH3

m

4x

x ' @ sulfide or thioether crosslin/

x @ polysulfide crosslin/

4

N

4 H

mercaptobenzothiazole

;#+/

4

N

4 4x

H

a hypothetical intermediate

acelerated !ulcanization

7ulcanization

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Condensation Polymerization

9noles the condensation of t"o different bifunctional monomers% resulting in the

elimination of a small stable molecule (H&O% HCl% 0OH)= 9t essentially inoles a

nucleophilic acyl substitution by one nucleophilic monomer on the electrophilic monomer=

Examples:

4) Poly(amide) 8ynthesis% e=g= ylon 1%1

C

O

HO CH2/* C

O

OH

hexanedioic acid

(adipic acid)

: (CH&)1H2N NH2

4%1-hexanediamine

n n (CH&)1HN NH C

O

CH2/* C

O

n

: &n H&O

 ylon 1%1

aporiz

"hich dr 

the react

1 carbons in diamine1 carbons in the acid

 

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CH2/DHN NH C

O

CH2/* C

O

CH2/DH2N NH2 HO C

O

CH2/* C

O

OH

HO C

O

CH2/* C

O

CH2/DHN NH2

CH2/DHN NH2

HO C

O

CH2/* C

O

O

H

H

HO C

O

CH2/* C

O

OH CH2/DH2N NH2

CH2/DH2N NH2

HO C

O

CH2/* C

O

OH

:

:

: H&O

n

amide lin!age

;echanism

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R2O O C

O

R@ C

O

R2HO HO C

O

R@ C

O

OH

HO C

O

R@ C

O

R2O

R2HO OH

HO C

O

R@ C

O

O

H

H

HO C

O

R@ C

O

OH R2HO OH

R2HO OH

HO C

O

R@ C

O

OH

:

: H&O :

n

ether lin!age

OH

OH

&) Polyester 8ynthesis e=g= P > polyethylene aphthalate

#echanism?

HO CH2 CH2 OH

C

O

HO

C

O

OHn : n

High temp and pressure

acid buffer pH 5-2

C

O

O

C

O

O CH2 CH2

n

: &n H&O

 aphthalene dicarboxylate

ethylene glycol

 poly(ethylenenaphthalate)

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3) Polycarbonate% or specifically polycarbonate of bisphenol $% is a clear plastic used to ma!e

shatterproof "indo"s and light"eight eyeglass lenses= eneral lectric sells it as @exan=

HO C

CH3

CH3

OH

;isphenol $

n : n O C

O

O aOH

O C

CH3

CH3

O C

O

n

: &n HO

or 

HO C

CH3

CH3

OH

;isphenol $

n : n C

O

ClCl

O C

CH3

CH3

O C

O

n

: &n HCl aOH

diphenyl carbonate

 phosgene 

HO OH C

O

Cl Cl

RHO O CO

ClCl

H

:

-HClRHO O C

OCl

RHO OH

RHO O C

O

O R OH

H

:Cl

-HClRHO O C

O

O R OH

C

O

Cl Cl

etc

0 

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Addition reactions

4) Poly(urethane) 8ynthesis

Polyurethanes are the most "ell !no"n polymers used to ma!e foams li!e foam cushions= Polyurethanes can also

 be used as in paints% synthetic fibers% and they can also be used as adhesies=

 otice that in the mechanism not only monomers react% but also dimers% trimers% and so on= This ma!es it a step

gro"th polymerization= $lso% because no small molecule by-products are produced% it is called an addition

 polymerization

N CH2 N C OCO

a di-isocyanate

n HO CH2 CH2 OH

ethylene glycol

: n

H3O:

catlyst

N CH2 N CC

H

O O

O

H

CH2 CH2 O

nurethane

lin!age

9n this reaction there

is not a loss of a smallmolecule

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CO N CH2 N C O HOOH

:

0 

0  N C OH

:

0  N C O H:

HO R2 0  N C

OH

O

H

R:

0  N C

OH

O R2

H

:0  N C

OH

O R2

H

:0  N C

O

O R2

H

etc

urethane lin!age

0 &

-H:

catalyst

:

;echanism

8ometimes% instead of using a small diol li!e ethylene glycol% a polyglycol% one "ith a molecular "eight of

about &666 can be used= This produces a polymer "ithin a polymer and polyurethane that loo!s something li!e

this?

8pandex N CH2 N CC

H

O O

O

H

CH2 CH2 O

n

soft rubbery bloc! hard rigid bloc! 

 x

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N CH2 N C OCO

a di-isocyanate

n H2N CH2 CH2 NH2

ethylene diamine

: n

N CH2 N CC

H

O O

N

H

CH2 CH2 O

n

urealin!age

H

Polyurea

8f a diamine is used instead of a diol in this reaction a polyurea is made

CO N CH2 N C O H& NH2:

0 

0  N C OH

:

0  N C O H

:

H&  R2 0  N C

OH

N

H

R

:

0  N C

OH

N R2

H:

0  N C

OH

N R2

H

:0  N C

O

N R2

H

etc

urea lin!age

0 &

-H:

catalyst

:

H

H

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C

O

H2N NH2C

O

H H

:H:

C

O

H H

H:

C

O

H

HH

N

C

H H

O

NH2:

C

OH

HH

N

C

H

O

NH2

H:

C

O

H2N NH2

-H&OC

N

C

H

O

NH2NC

O

H2N

H

H

H

:

etc

3) /rea-+ormaldehyde (a polyurea plastic)

n C

O

H2N NH2

ureaformaldehyde

C

O

H H

 pH 5-7: n

N N N NCH2

O

H H H

O

H n 

#echanism

;elamine - ormaldehyde resinsformaldehyde

C

O

H H

: nN N

N NH2

NH2

H2N

n pH 5-7

N N

N N

N

HNH

NN

N

HN

H

NN

NN

N

H

H

n

n

n

cross-lin!ed polyurea

melamine

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Phenol-ormaldehyde Resins E #aelite used for heat and electrical

coatin"s

formaldehyde

C

O

H H

OH

n : n

 pH 5-7

OH OH

HO

HO

HO

OH

 phenol

a crossed polyol

;echanism

H

O

H

H

H

O

H

H

H

O

H

H

HO

H

H

H

-H

HO

H

H

H

O

H

H

HH

-H2O

HH

OH

OH

OH OH

OH OH

HOHO HO

OH

H

H

HO HO

OH OH

etc

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Nucleophilic 4ubstitution Reactions formin" polyethers

A/ :poxy Resins Hi"hly cross-lined polyethers made from epoxide

monomers

O ClHO

CH3

CH3

OH

O

CH3

CH3

O

OCl O Cl

epichlorohydrin

bisphenol-8

NaOH

A= - @== o  C

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OH2CHC

O

H2CCl

CH3

CH3

O CH2 CH

O

CH2 Cl

OH2CHC

O

H2C

CH3

CH3

O CH2 CH

O

CH2

0 

HC

O

H2C CH2

CH3

CH3

O O O R

CH3

CH3

O O CH2 CH CH2

O

O R

etc

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:poxy "lues often consist of t)o components )hich the user mixes Fust

before the desired &"luin" & process. One component is the polymer sho)n

abo!e. +he other component is often ethylene diamine. :thylene diamine

reacts )ith the epoxide &end& "roups of the epoxy resin sho)n abo!e to

effect rin" openin" to form amino alcohols. :ach amino "roup can react )itht)o epoxide "roups so that the resultant system is a net)or of cross-lined

polymers )hich ha!e !ery stron" adhesion properties. +he process of

formin" this net)or of cross-lins is called &curin" &.

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O

CH3

CH3

O

OH

n

OO

CH3

CH3

O

O

H2N

NH2

O

CH3

CH3

O

OH

n

OH

O

CH3

CH3

O

OH

N

N

N

N

O

CH3H3C

O

OH

OH

O

H3CCH3

O

OH

O

H3C CH3

O

HO

HO

O

CH3

H3C

O

HO

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rom the )eb site( Plastic polymers(

http(99))).rsc.or"9lap9educatio9eic92==39hi""insGmay=3.htm

Prior to the @>=Is all synthetic polymers )ere insulated

ConFu"ated polyacetylene )as one of the first conductin" polymers

#ut hard to )or )ith E insoluble E unstable0 sensiti!e to oxy"en.

Polythiophene and polyohenyle!inylene E less sensiti!e to oxy"en

 -- more stable E lon" chain bacbones could be attached to the polymers

to mae them more soluble in non-polar sol!ents.

%hy are they conductin"J ar"e number of delocalized π bondin"

electrons allo)s mo!ement alon" seletal structure.

Conducting Polymers

Conductin" polymers $CPs/ ha!e attracted much attention because of their potential applications in

or"anic li"ht emittin" diodes O:1s/0 printed circuits0 chemical sensors0 electronic s)itches0

rechar"eable batteries0 electrolytic capacitors0 smart )indo)s0 :;$ shieldin" and electrostatic char"edissipation :41/ coatin"s. $n spite of the thousands of papers published and patents filed in this field0

the number of commercial applications of $CPs is still small. Poor lon" term stability and lac of

reasonable processin" methods ha!e been the maFor sho)stoppers to the commercialization of $CPs.

+18Ks research on $CPs has focussed on impro!in" the sol!ent processability of conductin" polymers

)ith pro!en stability0 includin" poly30*-ethylenedioxythiophene/ P:1O+/ and polypyrrole.

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Organic-Processable PEDOT:

Materials that combine electronicconductivity with optical clarity aresought for the fabrication of flat paneldisplays and other electronic devices.PEDOT has excellent transparency in thevisible region, good electricalconductivity, and environmental

stability. nfortunately PEDOT, li!e mostconducting polymers, is infusible andinsoluble and therefore difficult toprocess in a thin"film form or in othershapes. #ac! of processability has beena ma$or impediment to the commercialacceptance of this polymer. % water dispersion of PEDOT doped withpoly&styrenesulfonate' &P((' is available from ).*. (tarc! under the trade name of

+aytron

 

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http966quar*.physics.uwo.ca6;smittler6ilvia

nctionalisation.htm

Potential use in medicine' computing and telecommunication >

molecular switches

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angmuir Trough

Amphiphilic +olecules (oap)

connection between hydrophilic and

hydrophobic liquids

Compression organizes monolayer 

+onolayer can be transferred onto a solid

support

hydrophobic

hydrophilic

hydrophilic

bilayers can also be made

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-ne of the focuses of our research is the development of novel molecular

electronic devices. That is' devices made from a hybridization of conventional

semiconductor fabrication methods and self%assembling synthetic molecules

which have unique and useful electronic characteristics. ?e presently utilize a

brea* @unction method for ma*ing two terminal electrical contact to single

molecule. ?e also have a method for ma*ing electrical contact to both sides of a

molecular A+ (self%Assembled +onolayer)9 the nanopore. ,sing these

measurement tools we have identified molecules which wor* well as insulators'

conductors' diodes' two%terminal switches and random access memory cells.

+olecular witch

http966www.eng.yale.edu6reedlab6research6device6moldevices.htmlBoverview

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The conduction path in a

conventional microelectronics

transistor 

is turned on using an applied

voltage at the gate electrode.

imilarly' the conduction path

through a molecular switch is

turned on by an applied voltage.

The applied voltage is believed to

cause a conformational shift

which' in concert with the

charging of the molecule' opens

the conduction pathway.

http966www.eng.yale.edu6reedlab6research6device6moldevices.htmlBoverview

+olecular witch

(

!

-!

C

-

C2

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:lectroactive Polymers as Artificial +uscles % A Primer (D. E. Cohen) 

http(99))).polysep.ucla.edu9ResearchB2=8d!ances9:8P9electroacti!eGpol

:lectroacti!e polymers :8Ps/ are touted as the basis for future artificial muscles. :8Ps can bedeformed repetiti!ely by applyin" external !olta"e across the :8P0 and they can ,uicly reco!er theirori"inal confi"uration upon re!ersin" the polarity of the applied !olta"e. +o explore the potential useof :8PIs as artificial muscles0 a brief e!aluation is presented of an ionic-based :8P composite as acandidate artificial muscle material. +he electromechanical properties of the :8P under dry and moistconditions are presented alon" )ith the :8PIs performance under load conditions. 84 sho)n throu"ha series of simple tests0 the :8P has a hi"h load bearin" capacity to mass ratio0 short response time0

and nearly linear deformation response )ith respect to applied !olta"e 

http://www.polysep.ucla.edu/Research%20Advances/EAP/electroactive_polymers_as_artifi.htmhttp://www.polysep.ucla.edu/Research%20Advances/EAP/electroactive_polymers_as_artifi.htm

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$llustration of an :8P-po)ered forceps. a/ forceps open? b/ forceps closes upon polarity re!ersal?

c/ and d/ lift action.

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Lpon the application of an electrical field across a moist :8P0 )hich is held bet)een metal electrodes

attached across a partial section of an :8P strip0 bendin" of the :8P is induced. Positi!e counterions mo!e to)ards the ne"ati!e electrode cathode/0 )hile ne"ati!e ions that are fixed or immobile/to the polymer e.". 4O

3/ experience an attracti!e force from the positi!e electrode anode/. 8t the

same time0 )ater molecules in the :8P matrix diffuse to)ards the re"ion of hi"h positi!e ionconcentration near the ne"ati!e electrode/ to e,ualize the char"e distribution. 8s a result0 the re"ionnear the anode s)ells and the re"ion near the cathode de-s)ells0 leadin" to stresses )hich cause the:8P strip to bend to)ards the positi!e anode.