化學(xué)專業(yè)英語-Polymer課件

PolymerChemistryIntroductiontopolymersSynthesisStructureandpropertiesCharacterization1.Introductiontopolymers1.1Polymer

Polymersarelargemoleculesmadeupofsimplerepeatingunits.ThenameisderivedfromtheGreek

polymeaning“many”andmer

meaning“part”.Macromoleculeisatermsynonymouswithpolymer.1.3Classificationofpolymers

1.3.1Homopolymerandcopolymer

（均聚物和共聚物）

Ifonlyonetypeofmonomerisemployedtoformthepolymertheresultingmoleculeiscalledahomopolymer.Oftenpropertiesareobtainedbyusingdifferenttypesofmonomerspecies.Inthiscasethepolymeristermedacopolymer.

1.3.2Linear,branchedandnetworkpolymer（線形，支化，網(wǎng)狀高分子）LinearBranchedNetwork(crosslinked)1.3.3ThermoplasticandThermoset（熱塑和熱固塑料）

?

Whatis

thermosetting.?

?Whatisthermoplastic?

Thermoplasticpolymersarereadilymoldable

andcanbecastfromsolutiontogivefilms.1.3.4OtherClassifications

RubbersPlasticsFibersCoatingsAdhesives2.1Step-growthpolymerization

（逐步聚合）

Step-growthpolymerization,whichisoftenalsocalledcondensationpolymerization（縮聚）sinceitisalmostexclusivelyconcernedwithcondensationreactiontakingplacebetweenmultifunctionalmonomermolecules.2.1.1Condensationreaction

（縮合反應(yīng)）

Atypicalcondensationreactionisthereactionbetweenaceticacidandethylalcohol

Twoimportantpointstonotearethatasmallmolecule,water,isproducedbythereaction.Alsotheproductethylacetateisknownasanester.2.1.3Carothersequation（卡羅瑟斯方程） Carothers,whowasapioneerofstep-growthpolymerizationproposedthattherewasasimplerelationshipbetweenthenumberaveragedegreeofpolymerization,andtheextentofreaction,p.

Extentofreaction（反應(yīng)程度）,p

,attimetisdefinedastheprobabilitythatanyfunctionalgrouppresentinitiallyhasreacted

Thenumberaveragedegreeofpolymerization（數(shù)均聚合度）,，isgivenby2.1.4Linearstep-growthpolymerizationsystemEsterinterchangereactionSaltdehydrationRing-openingpolymerization2.1.5Non-linearstep-growth

polymerizationsystem

Ifatriolisreactedwithadiacid,abranched

ratherthanalinearchainwillform.Thebranchedchaincangoonbyfurthercondensationreactionstoformcomplexthree-dimensionalnetworkstructureswhichhavephysicalandmechanicalpropertieswhicharequitedifferentfromthoseoflinearpolymers.2.2Freeradicaladditionpolymerization（自由基加成聚合）

Additionpolymerizationisthesecondmaintypeofpolymerizationreaction.Ittakesplaceinthreedistinctsteps:initiation,propagationandtermination,andtheprincipalmechanismofpolymerformationisbyadditionofmonomermoleculestoagrowingchain.Therearesufficientdifferencesbetweenfreeradicalandionicinitiatedreactionsforthetwotypestobetreatedseparately.2.2.1FreeradicalinitiatorsFreeradicalmaybereadilyproducedbythethermaldecompositionofcertainperoxidesandazocompounds.Azocompoundswilldecomposebothwiththeapplicationofheatandbyphotolysis.Chemicalreactionssuchasredoxreactionsmaybeusedtoproduceradicalsandtheyareparticularlyusefulfortheinitiationofpolymerizationatlowtemperatureorforemulsionpolymerization.2.2.3Propagation

Chainpropagation

takesplacebytherapidadditionofmonomermoleculestothegrowingchain

andthiscanbewritten,ingeneral,ignoringtheradicalfragmentsas Theaveragelife-timeofthegrowingchainareextremelyshortandseveralthousandadditioncantakeplacewithinafewsecond.2.2.4Termination

disproportionation（歧化）chaintransfer（鏈轉(zhuǎn)移）2.3Ionicpolymerization

（離子聚合）

Ionicpolymerization

systemshavebeendevelopedbecausesomemonomerswhichcontaindoublebondscannotbepolymerizedusingfree-radicalinitiators.Alsoionicpolymerizationgenerallytakesplaceatlowtemperaturesandcanofferbettercontrolofstereoregularityandrelativemolecularmassdistribution.2.3.1Cationicpolymerization

（陽離子聚合）

Thistypeofpolymerizationtakesplacebytheadditionofmonomermoleculestoapositivelychargedgrowingchain,knownasacarboniumion.2.3.2Anionicpolymerization

（陰離子聚合）

Anionicpolymerizationinvolvesthesuccessiveadditionofmonomerswhichcontaindoublebondstoanegativelychargedspeciesknownasacarbanion.

Classificationofcopolymers

Thereareseveralwaysinwhichmonomerscanbearrangedinthemacromolecules.RandomcopolymersAlternatingcopolymersBlockcopolymersGraftcopolymersRandomcopolymers（無規(guī)共聚物）

-A-B-A-A-B-A-B-B-B-A-A-B-

TrulyrandomcopolymersareonlyfoundunderspecificpolymerizationconditionsAlternatingcopolymers（交替共聚物）

-A-B-A-B-A-B-A-B-A-B-A-B-A-B-

Thistypeofcopolymersisformedduringcondensationpolymerizationwhentwodifferenttypesofmonomersuchasdiacidanddiolareused.Blockcopolymers（嵌段共聚物）

-A-A-A-A-A-B-B-B-B-B-A-A-A-A-A-

Sometimestheblockcopolymerismadeupofjusttwoorthreelongblocksofeachtypeofunitgivingamaterialwithinterestingandunusualproperties.Graftcopolymers（接枝共聚物） -A-A-A-A-A-A-A-A-A-A-A-A-A-A-A-A-BBBBBBBB

Ingeneralitisfoundthatblockandgraftcopolymershavepropertiesofboththehomopolymerswhereasalternatingandrandomcopolymerspossesspropertiessomewherebetweenthoseofthetwohomopolymers.3StructuresandProperties

3.1Molarmass（摩爾質(zhì)量）

Molarmass(M)ofthepolymeristhe‘themassofonemoleofthepolymer’andsohasunitsofgmol-1orkgmol-1.Anormalpolymersamplecontainsmoleculeswithavarietyoflengthsanditisonlypossibletoquoteanaveragevalueofmolarmass.Oftentheterm‘molecularweight(分子量)’isstillusedinsteadofmolarmass. (1)Thenumberaveragemolarmass（數(shù)均摩爾質(zhì)量）,isdefinedas‘thesumoftheproductofthemolarmassofeachfractionmultipliedbyitsmolefraction’i.e. whereXiisthemolefractionofmoleculesoflengthi,theratioofthenumberofmoleculesoflengthitothetotalnumberofmolecules.

(2)Theweightaveragemolarmass(重均摩爾質(zhì)量）,

isdefinedas‘thesumoftheproductofthemolarmassofeachfractionmultipliedbyitsweightfraction’ i.e. wherewiistheweightfractionofmoleculesoflengthi,theratioofthemassofmoleculesoflengthitothetotalmassofallmolecules.

3.1.1MeasureofaveragemolarmassEndgroupanalysis（端基分析法）Cryoscopyandebulliometry（冰點(diǎn)和沸點(diǎn)測定法）Osmometry（滲透壓法）Lightscattering（光散射法）Ultracentrifugation（超速離心法）Viscometry（粘度法）Viscosity（粘度）1.Relativeviscosity(相對粘度，viscosityratio) Inthisexpression,and0refertosolutionandsolventviscosity,respectively,inpoiseunitswhichareproportionaltothecorrespondingflowtimes,tandt0,throughtheviscometercapillary.

Relativeviscosityisdimensionless.

2.Specificviscosity（增比粘度）

Specificviscosityisalsodimensionless. 3.Reducedviscosity(比濃粘度，viscositynumber)

4.Inherentviscosity(比濃對數(shù)粘度，logarithmicviscositynumber)5.Intrinsicviscosity(特征粘度，limitingviscositynumber)

Concentration,C,intheaboveexpressionsisingramsper100mlofsolvent;thereforereduced,inherent,andintrinsicviscositieshaveunitsofdeciliterspergram.Mark-Houwinkequation whereKandareconstantswhichdependonthenatureofpolymerandthesolvent.IntrinsicviscosityisrelatedtomolarmassaccordingtoMark-Houwinkequation.ThemolarmassobtainedbytheMark-Houwinkrelationshipisreferredtoastheviscosityaveragemolarmass.

3.1.2MolarmassdistributionUltracentrifugation（超速離心法）Fractionalprecipitation（沉淀分級法）Fractionalsolution（溶解分級法）Gelpermeationchromatography（凝膠滲透色譜法）Thinlayerchromatography（薄層色譜法）3.2StereochemistryIn1963,ZieglarandNattawontheNobelPrizeinChemistryfortheirdiscoveriesthatledtothedevelopmentofstereoregularpolymers.3.2.1StructuralisomerismBranchingOrientations

head-to-tail head-to-head3.2.2Configurationalisomerism Forpolymerspreparedfrommonomersoftype,therearetwopossiblestereoregulararrangements-oneinwhicheachcarbonbearingtheRgrouphasthesameconfiguration,andoneinwhichalternatecarbonsbearingtheRgrouphavethesameconfiguration.Nattaproposedthetermsisotactic（全規(guī)）fortheformerandsyndiotactic（間規(guī)）forthelatter.Acompletelyrandomdistributioniscalledatactic（無規(guī)）.3.3Crystallinity（晶態(tài)）Whenapolymerhasahighlystereoregularstructurewithlittleornochainbranchingorwhenitcontainshighlypolargroupsthatgiverisetostrongdipole-dipoleinteractions,itcanexistincrystallineform.Fringedmicellemodel(纓狀膠束模型)Foldedchainlamellamodel(折疊鏈結(jié)構(gòu)模型)Switchboardmodel(插線板模型)Crystallinemeltingpoint（晶體熔點(diǎn)）,Tm

Forcrystallinepolymers,thetemperatureatwhichcrystallinitydisappearsisfrequentlyused.Thisiscalledcrystallinemeltingpoint,anditismostconvenientlymeasuredbyobservingthedisappearanceofcrystallinebirefringenceunderapolarizingmicroscope.Meltingpointofpolymersisalsoreferredtoasfirst-ordertransitiontemperature.3.4Glasstransitiontemperature（玻璃化溫度）,Tg

Allpolymers,attemperaturesbelowacertainlevel,exhibitpropertiescharacteristicofabrittlesolidorglass.Asthetemperatureisraised,apointisreachedwherethepropertiesofthepolymerchangetothoseofarubber.Thistemperatureiscalledtheglasstransitiontemperature,Tg.Itdiffersfromthemeltingpoint,wherethepolymerchangesfromthesolidtotheliquidstate;rather,itmarksthetemperatureatwhichmajorsegmentsofthepolymerchainsgainsometranslationalfreedom.Inotherwords,thepolymerisnolongerheldinarigidstatewithmotionrestrictedtovirbrationalmovementsofindividualatoms,butsectionsofpolymerchainsbegintomove.Inadditiontostiffness,polymersexhibitmarkedchangesinotherproperties,suchasrefractiveindex,thermalconductivity,andspecificvolumeattheglasstransitiontemperature.Infact,onecanmeasureTgbyplottingspecificvolumeagainsttemperatureandnotingthetemperatureatwhichthereisachangeinslope.Moreconveniently,canbemeasuredbydifferentialthermalanalysis. BecausethechangesthatoccuratTgarenotsomuchinphysicalstate,aswithTm,butratherinthermodynamicproperties,theglasstransitiontemperatureisalsoreferredtoasthesecond-ordertransitiontemperature.3.5Flameresistant

Manypolymers–forexample,poly(vinylchloride)andotherhalogen-containingpolymers–arenotflammable.Others,suchaspolyurethanes,burnpoorlyorstopburningwhenthesourceofflameisremoved.Thelattertypearesaidtobe“self-extinguishing”.Whilethemechanismofburningisnotwellunderstood,itisknownthatcertainelements,whenincorporatedintopolymerseitherasfillersorasanintegralpartofthepolymerstructure,retardorpreventburning.Thedegreeofpreventiondepends,ofcourse,onconcentration.Amongthevariouselementsthathavebeentested,halogen,phosphorus,andantimonyhavebeenreceivedmostattention.3.6ThermalstabilityWhenorganicsubstancesareheatedtoveryhightemperature,theyhaveatendencytoformaromaticcompounds.Itfollows,then,thataromaticpolymersshouldberesistanttohightemperature.Awidevarietyofpolymershavingrepeatingaromaticunitshavebeendevelopedinrecentyearswithmuchoftheimpetuscomingfromtheneedoftheaerospaceindustriesforhigh-performancematerialsthatwillwithstandextremesoftemperature.Inadditiontothermalandoxidativestability,aromaticpolymersfrequentlydisplaymuchbetterresistancetoionizingradiationthandononaromaticpolymers.3.7ChemicalresistanceOneoftheproblemsthatoilcompaniesfacewith:petroleumstoragetanksisrustingawayofmetalbottombymoisturefromunderneath.Remedy:bysprayinginsideonthetankbottomamixtureofunsaturatedpolyesterinstyreneandchoppedglassfibersforreinforcing.

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