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POLYMERS

An Introduction

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POLYMER SCIENCE

POLYMER CHEMISTRY

POLYMER PHYSICS

3.1.1 Polymers & Macromolecules

3.1.2 Polymer Synthess

3.1.3 Physcal Polymer Chemstry

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POLYMER SCIENCE

! Most polymer research may be categorized as

polymer science, a sub-discipline of materials science 

which includes researchers in chemistry (especially

organic chemistry), physics, and engineering. Polymer

science may be roughly divided into two

subdisciplines:

! Polymer chemistry or macromolecular chemistry,

concerned with the chemical synthesis and chemical

properties of polymers.

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Basic concepts in polymer chemistry

! Polymers and macromolecules

  In chemistry, the terms "polymer molecule" nd"mcromolecule" re used interchn!ely. #$%. Apolymer molecule hs hi!h moleculr mss ndis comprised o& mny smller, repetin! suunitsor monomers. Polymers my e &ound in nture,

such s the 'NA nd proteins &ound in li(in! cells,or creted in lortories or &ctories.Polymer molecules come in mny shpes ndsi)es. A polymer molecule my e lon! chin o& sin!le monomer repeted o(er nd o(er !inor comple* net+or continin! do)ens o&di-erent types o& monomers. he identity, (riety,nd rrn!ement o& monomers in polymermolecule -ect the chemicl nd physiclproperties o& the polymer molecule.

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/Smple o& polymers 0mcromolecules

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Polymer synthesis

An importnt re o& reserch in polymerchemistry is 1ndin! ne+ or etter +ys toprepre polymer molecule &rom stoc o&smller monomers.In most cses, polymers re prepred usin!principles o& or!nic chemistry. Polymer chemistsre especilly interested in techni2ues tht llo+them to precisely control the si)e nd structure o&the end product.Polymer chemists re lso in(esti!tin!polymeri)tion methods outside the scope o&

or!nic chemistry. One re o& interest in(ol(espreprin! polymers y imittin! the iolo!iclprocesses used to crete iopolymers such sproteins or cellulose. Other res o& study in(ol(eusin! plsm or electricity to inititepolymeri)tion rections.

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! Physical polymer chemistry is the study of howa polymer molecule's structure relates to thebehavior of the bulk substance.

! Physical polymer chemistry is closely related tothe eld of polymer physics and also overlapswith polymer research in materials science.

! Physical polymer chemists use analyticaltechniques such as light scattering andspectroscopy to characterize the size and

structure of polymers.Other areas of interest in physical polymerchemistry include the study of polymers insolution the mechanical properties of polymersand understanding phase transitions in polymersubstances. !here are also many researchers

using principles of theoretical chemistry tobetter understand the structure and propertiesof polymer molecules.

" spectroscopy#the science that deals with the useof the spectroscope and with spectrum analysis. 

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Polymer physics

  Concerned +ith the ul properties o& polymermterils nd en!ineerin! pplictions. he 1eld o&polymer science is !enerlly concerned +ithsynthetic polymers, such s plstics, or chemicltretment nd modi1ction o& nturl polymers.

! Polymer physics is the 1eld o& physics ssocited tothe study o& polymers, their 3uctutions,mechnicl properties, s +ell s theinetics o& rections in(ol(in! de!rdtion ndpolymeristion o& polymers nd monomers respecti(ely.

4hile it &ocuses on n spect o& the study o&condensed mtter physics , the 1eld o& polymer physicshs de(eloped s rnch o& sttisticl physics.Polymer physics nd polymer chemistry re prt o& the+ider 1eld o& polymer science.

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'isordered polymers re too comple* to edescried usin! deterministic method. 5o+e(ersttisticl pproches cn yield results nd reo&ten pertinent since lr!e polymers 6tht is to sy,polymers +hich contin lr!e numer o&monomers7 cn e descried e8ciently s systemst the thermodynmic limit.

 herml 3uctutions continuously -ect the shpe

o& polymers in li2uid solutions, nd modellin! theire-ect re2uires recourse to the principles o&sttisticl mechnics. As corollry temperturestron!ly -ects the physicl eh(ior o& polymersin solution.

 he sttisticl pproch to polymer physics issed on n nlo!y et+een polymer nd either ro+nin motion, or some other type o&rndom +l. he simplest possile polymer modelis presented y the idel chin, corresponds to

homo!eneous rndom +l.

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!  he study o& iolo!icl polymers, theirstructure, &unction, nd method o& synthesis is

!enerlly the pur(ie+ o& iolo!y, iochemistry,nd iophysics.

!  hese disciplines shre some o& theterminolo!y &milir to polymer science,especilly +hen descriin! the synthesis o&iopolymers such s 'NA or polyscchrides.

! 5o+e(er, us!e di-erences persist, such sthe prctice o& usin! the term mcromolecule to descrie lr!e non/polymer molecules nd

comple*es o& multiple moleculr components,such s hemo!loin. Sustnces +ith distinctiolo!icl &unction re rrely descried in theterminolo!y o& polymer science. 9or e*mple, protein is rrely re&erred to s copolymer.

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"e#nton

PolymerPolymer literlly mens :mny prts.;

A polymeric solid mteril my econsidered to e one tht contins

mny chemiclly onded prts or units+hich themsel(es re onded to!etherto &orm solid.

Polymers comprise lr!e clss o&naturalnatural nd syntheticsynthetic mterils +ith(riety o& properties nd purposes.

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$atural polymers$atural polymers re &ound inmny &orms such s horns o&

nimls, tortoise shell, shellc 6&romthe lac eetle7, rosin 6&rom pinetrees7, nd tr &rom distilltion o&

or!nic mteril.

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Ty$es o# Polymers

 +o industrilly importnt polymericmterils re ruersruers nd plsticsplstics.

As en!ineerin! mterils, it is

pproprite to di(ide them into the&ollo+in! three cte!ories<

$.$. ElstomersElstomers

=.=.  hermoplstic Polymers hermoplstic Polymers

>.>.  hermosettin! Polymers hermosettin! Polymers

4here 6$7 re ruers nd 6=7 nd 6>7 re plstics4here 6$7 re ruers nd 6=7 nd 6>7 re plstics

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%lastomers

%lastomers%lastomers or ruers cn eelsticlly de&ormed lr!e mount

+hen &orce is pplied to them ndcn return to their ori!inl shpe+hen the &orce is relesed.

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&BB%&, A Nturl Polymer

One o& the most use&ul nturl polymers +sruer, otined &rom the sp o& the hevea tree.

It hs only limited use s it ecme rittle inthe cold nd melted +hen +rmed.

 he de(elopment o& vulcanizationvulcanization lter inthe nineteenth century impro(ed the durilityo& the nturl polymer ruer, si!ni&yin! the1rst populri)ed semi/synthetic polymer. heproperties +ere chn!ed min! the ruermore 3e*ile nd temperture stle.

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 he 1rst +holly synthetic polymer,

B()%*+!%B()%*+!%, +s introduced in $?@?.

Its ori!inl use +s to me illirdlls.

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Plastics

PlasticsPlastics re lr!e nd (ried !roupo& synthetic mterils +hich re

processed y &ormin! or moldin! intoshpe.

Plstics cn e di(ided into t+o clsses,

thermoplasticsthermoplastics nd thermosettingthermosetting

plasticsplastics dependin! on ho+ they restructurlly nd chemiclly onded.

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 hermoplstics (s. hermosets

!  hermoplstics

/little cross linin!

/ductile

/so&ten +hen heted

/polyethylene,

polypropylene,polycronte,polystyrene

!  hermosets

/lr!e cross linin!

/hrd nd rittle

/do not so&ten +ithhetin!

/(ulcni)ed ruer,epo*ies, polyesterresin, phenolic resin

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Reason %hy Polymers are Im$ortant

! Plstics cn e &ormed y moldin! intointricte prt shpes, usully +ith no&urther processin! re2uired

! Cost competiti(e +ith metls! enerlly re2uire less ener!y to

produce thn metl

! Certin plstics re trnslucentBtrnsprent +hich mes themcompetiti(e +ith !lss in somepplictions

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Polymers s En!ineerin!Mterils

! Ad(nt!es! Lo+ density relti(e to metls nd cermics

! ood stren!th/to/+ei!ht rtios &or certin polymers

! 5i!h corrosion resistnce

! Lo+ electricl nd therml conducti(ity

! Limittions

! Lo+ stren!th relti(e to metl nd cermics

! Lo+ modulus o& elsticity

! Ser(ice tempertures re limited to only &e+hundred de!rees

! iscoelstic properties, +hich cn e distinctlimittion in lod erin! pplictions

! Some polymers de!rde +hen suDected to

sunli!ht nd other &orms o& rdition

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!  he technolo!y to mss produce polymers+s not de(eloped until 4orld 4r II, +henthere +s need to de(elop synthetic ruer&or tires nd other +rtime pplictions ndnylon &or prchutes.

!  ody, polymers re commonly used inthousnds o& products s plstics, elstomers,

cotin!s, dhesi(es, s +ell s structurlcomponents &or products rn!in! &romchildrens toys to ircr&t.

!  hey me up F@G o& the or!nic chemicl

industry, since most o& them re sed oncron, +ith products produced tppro*imtely $H@ ! o& polymers per personnnully in S.

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Industry

!  ody there re primrily si* commoditypolymers in use, nmely polyethylene,polypropylene, poly(inyl chloride,polyethylene terephthlte, polystyrene nd polycronte. hese me upnerly ?FG o& ll polymers nd plsticsencountered in dily li&e.

! Ech o& these polymers hs its o+nchrcteristic modes o& de!rdtion ndresistnces to het, li!ht nd chemicls.

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Polyethylene

! Polyethylene 6IPAC nmepolyethene7 is thermoplstic commodity he(ily used inconsumer products.

! O(er J@ million tons o& the mterilre produced +orld+ide e(ery yer.

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Polypropylene

! Polypropylene or polypropene 6PP7 is thermoplstic polymer,mde y the chemicl industry 

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pplictions

! used in +ide (riety o& pplictions,includin! &ood pc!in!, ropes, te*tiles,plstic prts nd reusle continers o&

(rious types, lortory e2uipment,loudspeers, utomoti(e components,nd polymer nnotes. Additionlly it isused commonly in Ne+ Kelnd nd ythe S Militry s herml nder+er.

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Poly(inyl chloride

! Polyvinyl chloride, 6IPAC

 Polychloroethene7 commonlyre(ited P,-, is +idely usedthermoplstic polymer.

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pplictions

!  here re mny uses &or PC. As hrdplstic, it is used s (inyl sidin!,m!netic stripe crds, +indo+ pro1les,

!rmophone records 6+hich is the sourceo& the nme &or (inyl records7, pipe,plumin! nd conduit 1*tures. hemteril is o&ten used in

Plstic Pressure Pipe Systems &or pipelines in the +ter nd se+er industries ecuseo& its ine*pensi(e nture nd 3e*iility

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Polyethylene terephthlte

! Polyethylene terephthalate 6P%!, P%!% or the osolete PEP orPE/P7 is thermoplstic polymer resin o& the polyester &mily

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pplictions

! used in synthetic 1ers e(er!e,&ood nd other li2uid continersthermo&ormin! pplictions nd

en!ineerin! resins o&ten incomintion +ith !lss 1er. It is oneo& the most importnt r+ mterils

used in mn/mde 1ers.

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Polystyrene

! Polystyrene is polymer mde &romthe monomer styrene, li2uidhydrocron tht is commercilly

mnu&ctured &rom petroleum y thechemicl industry. At roomtemperture, polystyrene is normlly

solid thermoplstic, ut cn e meltedt hi!her temperture &or moldin! ore*trusion, then re/solidi1ed.

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Polycronte

! Polycarbonates re prticulr!roup o& thermoplstic polymers. hey re esily +ored, molded, ndthermo&ormed

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pplictions

! Plstics re (ery +idely used in themodern Chemicl industry.

!  heir interestin! &etures6temperture resistnce, impctresistnce nd opticl properties7position them et+eencommodity plstics nd en!ineerin! 

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Crcin! o& polymers

! Crcin! is the process y +hich polymer is di(ided into itssucomponents or monomers. heresultin! sucomponents re more(iscous thn the ori!inl polymer.

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Polymer egradation

! Chn!e in properties o& polymer

! Polymer sed product under the

in3uence o& one or more en(ironmentl&ctors

! It is o&ten due to the hydrolysis o& theonds connectin! the polymer chin,

+hich in turn leds to decrese in themoleculr mss o& the polymer.

! Chn!es my e undesirle or desirle

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Cont

!'e!rdtion o& polymers to &ormsmller molecules my proceed<

/ y rndom scission

/ y speci1c scission! 'e!rdtion process cn e use&ul

to pre(ent en(ironmentl pollution

/ Polylctic cid nd Poly!lycolic,cidused &or iomedicl ppliction

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 he chrcteri)tion o& polymerre2uires se(erl prmeters +hich need toe speci1ed. his is ecuse polymerctully consists o& sttisticl distriution

o& chins o& (ryin! len!ths, nd echchin consists o& monometer residues+hich -ect its properties.

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A (riety o& l techni2ues re used todetermine the properties o& polymers.

 echni2ues such s 

wide angle /#ray scattering,smll n!le /ry sctterin!, nd smll n!le neutron sctterin! re used todetermine the crystlline structure o&

polymers.  el permetion chromto!rphyis used to determine the numer (er!emoleculr +ei!ht, +ei!ht (er!emoleculr +ei!ht, nd polydispersity.

 

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9IR, Rmn nd NMR cn e used todetermine composition. herml properties

such s the !lss trnsition temperturend meltin! point cn e determined y di-erentil scnnin! clorimetry nd 

dynmic mechnicl nlysis. Pyrolysis&ollo+ed y nlysis o& the &r!ments is onemore techni2ue &or determinin! thepossile structure o& the polymer.

0 h l i l

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0orphologicalProperties

-rystallinity!  he stte +here in periodic nd

repetin! tomic rrn!ement ischie(ed y moleculr chinli!nment or ordered tomic rry.

! It my e*ist in polymeric mterils.! Its tomic rrn!ements +ill e more

comple* &or polymers.

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! 4hen pplied to polymers, the termcrystlline hs some+ht

mi!uousBuncler us!e.! Its crystls structure my e speci1ed in

terms o& unit cells +hich re 2uite

comple*.! In ddition to ein! entirely morphous

polymers my lso e*hiit (ryin!de!rees o& crystllinity.

(morphous h(in! non/crystl linestructure.

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! Interdispersed B ury dissol(ed +ithin

morphous res.

Polymers sin!le crystls my e !ro+n&rom dilute solutions s thin pltelets

nd h(in! chin/&olded structures.Mny semi/crystlline polymers &ormspherulites ech spherulites consists

o& collection o& rion/lie chin/&olded 6lmellr7 crystllites thtrdite out+rd &rom its center.

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ul PropertiesBMechniclProperties

 he ul properties o& polymer

re those most o&ten o& end/useinterest. hese re the propertiestht dictte ho+ polymer

ctully eh(es on mcroscopic scle.

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 ensile Stren!th 6ltimteStren!th7

 he ensile Stren!th o& mteril2unti1es ho+ much stress themteril +ill endure e&ore &ilin!.

EAMPLE<

  ruer nd +ith hi!her tensilestren!th +ill hold !reter +ei!he&ore snppin!.

In !enerl, tensile stren!th increses+ith polymer chin len!th.

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Mechnicl Chrcteristics o&Polymers

5i!hly sensiti(e<

! $. to the rte o& de&ormtion 6strin

rte7! =. emperture

! >. Chemicl Nture o& the

en(ironment 6presence o& +ter,o*y!en, or!nic sol(ent etc.7

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 Youn! Modulus o& Elsticity

 he prmeter 2unti1es the elsticityo& the polymers.

 he rtio o& stress 6stress it isinstntneous lod pplied to specimen di(ided y cross sectionlre e&ore ny de&ormtion7 to strin+hen de&ormtion is totlly elstic. Itis lso mesure o& the sti-ness o& mteril.

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 rnsport Properties

'i-usi(ity relte to ho+ rpidly moleculesmo(e throu!h the polymer mtri*.

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 he term meltin! point +hen ppliedto polymers su!!ests not solidli2uid phse trnsition ut

trnsition &rom CRYSALLINE ORSEMI/CRYSALLINE P5ASE to SOLI'AMORP5OS P5ASE. It is lso no+ns crystlline meltin! temperture.

Pure Com$onent Phase eha'or 

"##us'ty relate to ho( ra$)ly molecules

mo'e throu*h the $olymer matr+.

  Meltin! point 

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Boiling Point

e*. Amon! synthetic polymers, crystllinemeltin! is only discussed +ith re!rds to

thermoplstics, s thermosettin!polymers +ill decompose t hi!htemperture rther thn melt.

   he oilin! point o& polymersustnce is ne(er de1ned due tothe &ct tht polymers +illdecompose e&ore rechin!theoreticl oilin! tempertures.

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1lass !ransition !emperature

 he temperture t +hich, uponcoolin!, non/crystlline cermics or

polymer trns&orms &rom supercooled li2uid to ri!idBin3e*ile !lss.

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POLYMER SOLION E5AIOR

In !enerl, polymeric mi*tures re &r lessmiscile thn mi*tures o& smll moleculemterils. his e-ect is result o& the &cttht the dri(in! &orce &or mi*in! is usullyentropic, not ener!etic.

In other +ords, MISCILE MAERIALSusully &orm solution not ecuse theirinterction ut ecuse o& n increse in

entropy nd hence &ree ener!y ssocited+ith incresin! the mount o& (olume(ille to ech component. hisincrese in entropy scles +ith the numero& prticles 6or moles7 ein! mi*ed.

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C5EMICAL PROPERIES O9POLYMERS

The attract'e #orces ,et(een chans $lay alar*e $art n )etermnn* a $olymer-s $ro$ertes.ecause $olymer chans are so lon* these

nterchan #orces are am$l#e) #ar ,eyon) theattractons ,et(een con'entonal molecules."##erent s)e *rou$s o the $olymer can len) the$olymer to onc ,on)n* or hy)ro*en ,on)n*,et(een ts o(n chans. These stron*er #orces

ty$cally result n h*her tensle stren*th an)meltn* $ont.

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!he intermolecular forces in polymerscan be a2ected by dipoles in the monomerunits. Polymers containing amide orcarbonyl groups can form hydrogen bondsbetween ad3acent chains4 the partiallypositively charged hydrogen atoms in $#5groups of one chain are strongly attractedto the partially negatively charged o6ygenatoms in -7O groups on another. !hestrong hydrogen bonds for e6ample resultin the high tensile strength and meltingpoint of polymers containing urethane orurea linkages. Polyester have dipole#dipolebonding between the o6ygen atoms in -7Ogroups and the hydrogen bonding so apolyester8s melting point and strength are

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Ethene ho(e'er has no $ermanent )$ole.

The attract'e #orces ,et(een $olyethylene chans arse#rom (ea/ 0an )er %aals #orces.

Molecules can ,e thou*ht o# as ,en* surroun)e) ,y a

clou) o# ne*at'e electrons.

 s t(o $olymer chans a$$roach ther electron clou)sre$el one another. Ths has the e##ect o# lo(ern* the

electron )ensty on one s)e o# a $olymer chan creatn*

a sl*ht $ost'e )$ole on ths s)e. Ths char*e s

enou*h to actually attract the secon) $olymer chan.

0an )er %aals #orces are ute (ea/ ho(e'er so

$olyethene can ha'e a lo(er meltn* tem$erature

com$are) to other $olymers.

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 he hree Primry Methods

o& Polymer Synthesis

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! Polymers re synthesi)ed y threeprimry methods< or!nic synthesis in lortory or &ctory, iolo!icl

synthesis in li(in! cells ndor!nisms, or y chemiclmodi1ction o& nturlly occurrin!

polymers.

Or!nic s nthesis

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Or!nic synthesis

! In $?@, Leo eelnd creted the 1rstcompletely synthetic polymer, clled elite,y rectin! phenol nd &ormldehyde tprecisely controlled temperture nd pressure.

! Suse2uent +or y 4llce Crothers in the$?=@s demonstrted tht polymers could esynthesi)ed rtionlly &rom their constituentmonomers.

! Most commercilly importnt polymers todyre entirely synthetic nd produced in hi!h(olume, on ppropritely scled or!nicsynthetic techni2ues.

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! Lortory synthetic methods re!enerlly di(ided into t+o cte!ories,

condenstion polymeri)tion ndddition polymeri)tion. 5o+e(er,some ne+er methods such s plsm

polymeri)tion do not 1t netly intoeither cte!ory.

! Synthetic polymeri)tion rectionsmy e crried out +ith or +ithout ctlyst.

iolo!icl synthesis

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iolo!icl synthesis

Nturl polymers nd iopolymers &ormed in li(in!cells my e synthesi)ed y en)yme/meditedprocesses, such s the &ormtion o& 'NA ctly)edy 'NA polymerse. he synthesis o& proteinsin(ol(es multiple en)yme/medited processes to

trnscrie !enetic in&ormtion &rom the 'NA ndsuse2uently trnslte tht in&ormtion tosynthesi)e the speci1ed protein. he protein mye modi1ed &urther &ollo+in! trnsltion in order

to pro(ide pproprite structure nd &unction.

Modi1ction o& nturl

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Modi1ction o& nturlpolymersB Chemicl

Modi1ction! Mny commercilly importnt polymers

re synthesi)ed y chemicl

modi1ction o& nturlly occurrin!polymers. Prominent e*mples includethe rection o& nitric cid nd cellulose to &orm nitrocellulose nd the &ormtion

o& (ulcni)ed ruer y hetin! nturlruer in the presence o& sul&ur.

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  Polymer Structure nd

Properties

 ypes o& polymer QpropertiesQ cn e

rodly di(ided into se(erl cte!oriessed upon scle. At the nno/micro sclere properties tht directly descrie thechin itsel&. hese cn e thou!ht o& s

polymer structure. At n intermeditemesoscopic le(el re properties thtdescrie the morpholo!y o& the polymermtri* in spce. At the mcroscopic le(el

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  :tructure

!he structural properties of a polymer relateto the physical arrangement of monomersalong the backbone of the chain. :tructurehas a strong in9uence on the otherproperties of a polymer. ;or e6ample a linear

chain polymer may be soluble or insoluble inwater depending on whether it is composedof polar monomers <such as ethylene o6ide=or nonpolar monomers <such as styrene=. On

the other hand two samples of naturalrubber may e6hibit di2erent durability eventhough their molecules comprise the samemonomers. Polymer scientists havedeveloped terminology to precisely describe

both the nature of the monomers as well as

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0onomer identity

!he identity of the monomers comprising thepolymer is generally the rst and mostimportant attribute of a polymer. Polymernomenclature is generally based upon the

type of monomers comprising the polymer.Polymers that contain only a single type ofmonomer are known as homopolymers whilepolymers containing a mi6ture of monomersare known as copolymers. Poly<styrene= for

e6ample is composed only of styrene

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!acticity in polymers with chiralcenters

 his property descries the relti(estereochemistry o& chirl centers in

nei!horin! structurl units +ithin

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! Polymer ul properties my e stron!ly dependent on

the si)e o& the polymer chin. Lie ny molecule, polymer moleculeQs si)e my e descried in terms o&moleculr +ei!ht or mss. In polymers, ho+e(er, themoleculr mss my e e*pressed in terms o& de!ree o&polymeri)tion, essentilly the numer o& monomerunits +hich comprise the polymer. 9or syntheticpolymers, the moleculr +ei!ht is e*pressed sttisticllyto descrie the distriution o& moleculr +ei!hts in thesmple. his is ecuse o& the &ct tht lmost llindustril processes produce distriution o& polymerchin si)es. E*mples o& such sttistics include thenumer (er!e moleculr +ei!ht nd +ei!ht (er!emoleculr +ei!ht. he rtio o& these t+o (lues is the

polydispersity inde*, commonly used to e*press the"+idth" o& the moleculr +ei!ht.

!  he spce occupied y polymer molecule is !enerllye*pressed in terms o& rdius o& !yrtion or e*cluded(olume.

Chain size

0 t i

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  0onomer arrangement incopolymers

Monomers +ithin copolymer my e or!ni)edlon! the cone in (riety o& +ys.(lternating copolymers possess re!ulrlylterntin! monomer residues

Periodic copolymers h(e monomer residuetypes rrn!ed in repetin! se2uence&andom copolymers h(e rndom se2uence o&monomer residue types

:tatistical copolymers h(e monomer residuesrrn!ed ccordin! to no+n sttisticl ruleBlock copolymers h(e t+o or more homopolymersuunits lined y co(lent onds. loccopolymers +ith t+o or three distinct locs reclled diloc co ol mers nd triloc co ol mers

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!acticity in polymers

 his property descries the relti(e

stereochemistry in nei!horin!structurl units +ithin mcromolecule.