高分子材料工程专业英语翻译(DOC)

高分子材料工程专业英语翻译Unit1Whatarepolymers?Whatarepolymers?Foronething,theyarecomplexandgiantmoleculesandaredifferentfromlowmolecularweightcompoundslike,say,commonsalt.Tocontrastthedifference,themolecularweightofcommonsaltisonly58.5,whilethatofapolymercanbeashighasseveralhundredthousand,evenmorethanthousandthousands.Thesebigmoleculesor‘macro-molecules’aremadeupofmuchsmallermolecules,canbeofoneormorechemicalcompounds.。Toillustrate,imaginethatasetofringshasthesamesizeandismadeofthesamematerial.Whenthesethingsareinterlinked,thechainformedcanbeconsideredasrepresentingapolymerfrommoleculesofthesamecompound.，可以把形成的链看成是具有同种化合物组成的高聚物。Alternatively,individualringscouldbeofdifferentsizesandmaterials,andinterlinkedtorepresentapolymerfrommoleculesofdifferentcompounds.另一方面，环可以大小不同、材料不同,相连接后形成具有不同化合物组成的聚Thisinterlinkingofmanyunitshasgiventhepolymeritsname,polymeaning‘many’andmermeaning‘part’(inGreek).节、基体”(希腊语中)。Asanexample,agaseouscompoundcalledbutadiene,withamolecularweightof54,combinesnearly4000timesandgivesapolymerknownaspolybutadiene(asyntheticrubber)withabout200000molecularweight.的聚丁二烯(合成橡胶)高聚物。Thelowmolecularweightcompoundsfromwhichthepolymersformareknownasepictureissimplyasfollows形成高聚物的低分子化合物称为单体。下面简单地描述一下形成过程：丁二烯＋丁二烯＋…＋丁二烯——→聚丁二烯(4000次)Onecanthusseehowasubstance(monomer)withassmallamoleculeweightas54growtobecomeagiantmolecule(polymer)of(54×4000≈)200000molecularweight.分子(高聚物)。Itisessentiallythe“giantness”ofthesizeofthepolymermoleculethatmakesitsbehavior(differentfromthatofacommonlyknownchemicalcompoundsuchasbenzene.)实质上正是由于聚合物的巨大分子尺寸才使其性能不同于像苯这样的一般化合物(的性能)Solidbenzene,forinstance,meltstobecomeliquidbenzeneat5.5℃and,onfurtherheatingboilsintogaseousbenzene.Asagainstthiswell-definedbehaviorofasimplechemicalcompound,apolymerlikepolyethylenedoesnotmeltsharplyatoneparticulartemperatureintocleanliquid.融成纯净的液体。Instead,itbecomesincreasinglysofterand,ultimately,turnsintoaveryviscous,tackymoltenmass.Furtherheatingofthishot,viscous,moltenpolymerdoesconvertitintovariousgasesbutitisnolongerpolyethylene.(Fig.1.1).合物熔融体进一步加热，它会转变成不同气体，但它不再是聚乙烯(如图1.1)Anotherstrikingdifferencewithrespecttothebehaviorofapolymerandthatofalowmolecularweightcompoundconcernsthedissolutionprocess.聚合物行为和低分子量化合物另一不同的行为为溶解过程。Letustake,forexample,sodiumchlorideandadditslowlytofixedquantityofwater.Thesalt,whichrepresentsalowmolecularweightcompound,dissolvesinwateruptoapoint(calledsaturationpoint)but,thereafter,anyfurtherquantityaddeddoesnotgointosolutionbutsettlesatthebottomandjustremainsthereassolid.解直到某一点(叫饱和点)，但进一步添加,盐不进入溶液中却沉到底部而保持原有Theviscosityofthesaturatedsaltsolutionisnotverymuchdifferentfromthatofwater.Butifwetakeapolymerinstead,say,polyvinylalcohol,andaddittoafixedquantityofwater,thepolymerdoesnotgointosolutionimmediately.饱和盐溶液的粘度与水的粘度接近.但是，如果我们用聚合物，如聚乙烯醇添加到定量水中，聚合物不是马上进入到溶液中。Theglobulesofpolyvinylalcoholfirstabsorbwater,swellandgetdistortedinshapeandafteralongtimegointosolution.聚乙烯醇颗粒首先吸水溶胀，发生变形，经过很长时间后，(聚乙烯醇分子)进入Also,wecanaddaverylargequantityofthepolymertothesamequantityofwaterwithoutthesaturationpointeverbeingreached.们可以将大量的聚合物加入到同样量的水中，不存在饱和点。Asmoreandmorequantityofpolymerisaddedtowater,thetimetakenforthedissolutionofthepolymerobviouslyincreasesandthemixultimatelyassumesasoft,dough-likeconsistency.像面团一样粘稠的混合物。Anotherpeculiarityisthat,inwater,polyvinylalcoholneverretainsitsoriginalpowderynature[astheexcesssodiumchloridedoes][inasaturatedsaltsolution].另一个特点是，在水中聚乙烯醇不会像过量的氯化钠在饱和盐溶液中那样能保末状态。Inconclusion,wecansaythat(1)thelongtimetakenbypolyvinylalcoholfordissolution,(2)theabsenceofasaturationpoint,and(3)theincreaseintheviscosityareallcharacteristicsofatypicalpolymerbeingdissolvedinasolventandthesecharacteristicsareattributedmainlytothelargemolecularsizeofthepolymer.总之，我们可以讲(1)聚乙烯醇的溶解需要很长时间，(2)不存在饱和点，(3)粘度的增加是聚合物溶于溶液中的典型特性，这些特性主要归因于聚合物大分子的尺ThebehaviorofalowmolecularweightcompoundandthatofapolymerondissolutionareillustratedinFig.1.2.rizationManyolefinicandvinylunsaturatedcompoundsareabletoformchain-likemacromoleculesthrougheliminationofthedoublebond,aphenomenonfirstrecognizedbyStaudinger.Diolefinspolymerizeinthesamemanner,however,onlyoneofthetwodoublebondsiseliminated.Staudinger首先发现许多烯烃和不饱和烯烃通过打开双键可以形成链式大分子。二烯烃以同样的方式聚合，但仅消除两个双键中的一个。Suchreactionsoccurthroughtheinitialadditionofamonomermoleculetoaninitiatorradicaloraninitiatorion,bywhichtheactivestateistransferredfromtheinitiatortotheaddedmonomer.些反应活性中心由引发剂转移到被加成的单体上。Inthesamewaybymeansofachainreaction,onemonomermoleculeaftertheotherisadded(2000~20000monomerspersecond)untiltheactivestateisterminatedthroughadifferenttypeofreaction.单体分子通过链式反应以同样的方式一个接一个地加上(每秒2000~20000个单体)直到活性中心通过不同的反应方式终止。Thepolymerizationisachainreactionintwoways:becauseofthereactionkineticandbecauseasareactionproductoneobtainsachainmolecule.Thelengthofthechainmoleculeisproportionaltothekineticchainlength.OnecansummarizetheprocessasfollowRisequaltotheinitiatorradical):链式反应可以概括为以下过程(R·相当与引发剂自由基)：略Onethusobtainspolyvinylchloridefromvinylchloride,orpolystyrenefromstyrene,orpolyethylenefromethylene,etc.获得Thelengthofthechainmolecules,measuredbymeansofthedegreeofpolymerization,canbevariedoveralargerangethroughselectionofsuitablereactionconditions.分子链长通过聚合度测量，可以通过选择适宜的反应条件大为改变Usually,withcommerciallypreparedandutilizedpolymers,thedegreeofpolymerizationliesintherangeof1000to5000,butinmanycasesitcanbebelow500dover商业制备和使用的聚合物，聚合度通常在1000~5000范围内，但在许多情况下可Thisshouldnotbeinterpretedtomeanthatallmoleculesofacertainpolymericmaterialconsistof500,or1000,or5000monomerunits.Inalmostallcases,thepolymericmaterialconsistsofamixtureofpolymermoleculesofdifferentdegreesofpolymerization成。在几乎所有的情况下，聚合物材料由不同聚合度的聚合物分子的混合物组成。Polymerization,achainreaction,occursaccordingtothesamemechanismasthewell-knownchlorine-hydrogenreactionandthedecompositionofphosegene.链式聚合反应的机理与众所周知的氯(气)-氢(气)反应和光气的分解机理相同。Theinitiationreaction,whichistheactivationprocessofthedoublebond,canbebroughtaboutbyheating,irradiation,ultrasonics,orinitiators.Theinitiationofthechainreactioncanbeobservedmostclearlywithradicalorionicinitiators.楚地进行研究用自由基型或离子型引发剂引发的链式反应。heseareenergyrichcompoundswhichcanaddsuitableunsaturatedcompounds(monomers)andmaintaintheactivatedradicalorionicstatesothatfurthermonomermoleculescanbeaddedinthesamemanner.这些是高能态的化合物，它们能够加成不饱和化合物(单体)并保持自由基或离子活性中心以致单体可以以同样的方式进一步加成。Fortheindividualstepsofthegrowthreactiononeneedsonlyarelativelysmallactivationenergyandthereforethroughasingleactivationstep(theactualinitiationreaction)alargenumberofolefinmoleculesareconverted,asisimpliedbytheterm化反应(即引发反应)即可将许多烯类单体分子转化成聚合物，这正如连锁反应这个样。Becauseverysmallamountsoftheinitiatorbringabouttheformationofalargeamountofpolymericmaterial(1:1000to1:1000),itispossibletoregardpolymerizationfromasuperficialpointofviewasacatalyticreaction.因为少量的引发剂引发形成大量的聚合物原料(1：1000~1：10000)，从表面上看反应。Forthisreason,theinitiatorsusedinpolymerizationreactionsareoftendesignatedaspolymerizationcatalysts,eventhough,inthestrictestsense,theyarenottruecatalystsbecausethepolymerizationinitiatorentersintothereactionasarealpartnerandcanbefoundchemicallyboundinthereactionproduct,i.e.,thepolymer.应的催化剂进入到反应内部而成为一部分，同时可以在反应产物，既聚合物的末端发现催化剂，所以严格地讲它们不是真正意义上的催化剂，Inadditiontotheionicandradicalinitiatorstherearenowmetalcomplexinitiatorswhichcanbeobtained,forexample,bythereactionoftitaniumtetrachlorideortitaniumtrichloridewithaluminumalkyls),whichplayanimportantroleinpolymerizationreactions(Zieglercatalysts),Themechanismoftheircatalyticactionisnotyetcompletelyclear.除离子引发剂和自由基引发剂外，还有金属络合物引发剂(可以通过四氯化钛或三氯化钛与烷基铝的反应得到)。它们在聚合反应中起到了重要作用(齐格纳引发剂)。它们催化活动的机理还不是十分清楚。NITStepGrowthpolymerizationManydifferentchemicalreactionsmaybeusedtosynthesizepolymericmaterialsbystepgrowthpolymerizationTheseincludeesterification,amidation,theformationofurethanes,aromaticsubstitution,etc.化、氨基甲酸酯、芳香族取代物的形成等。Polymerizationproceedsbythereactionsbetweentwodifferentfunctionalgroups,e.g.,hydroxylandcarboxylgroups,orisocyanateandhydroxylgroups.Allstep-growthpolymerizationfallintotwogroupsdependingonthetypeofmonomer(s)employed.Thefirstinvolvestwodifferentpolyfunctionalmonomersinwhicheachmonomerpossessesonlyonetypeoffunctionalgroup.体，每一种单体仅具有一种官能团。Apolyfunctionalmonomerisonewithtwoormorefunctionalgroupspermolecule.Thesecondinvolvesasinglemonomercontainingbothtypesoffunctionalgroups.Thesynthesisofpolyamidesillustratesbothgroupsofpolymerizationreactions.Thus,polyamidescanbeobtainedfromthereactionofdiamineswithdiacidsorfromthereactionofaminoacidswiththemselves.之间的反应得到。Thetwogroupsofreactionscanberepresentedinageneralmannerbytheequations两种官能团之间的反应一般来说可以通过下列反应式表示Reaction.1)illustratestheformer,while(3.2)isofthelattertype.反应(3.1)说明前一种形式，而反应(3.2)具有后一种形式。Polyesterification,whetherbetweendiolanddibasicacidorintermolecularlybetweenhydroxyacidmolecules,isanexampleofastep-growthpolymerizationprocess.进行。Theesterificationreactionoccursanywhereinthemonomermatrixwheretwomonomermoleculescollide,andoncetheesterhasformed,it,too,canreactfurtherbyvirtueofitsstill-reactivehydroxylorcarboxylgroups.仍有活性的羟基或羧基还可以进一步进行反应。Theneteffectofthisisthatmonomermoleculesareconsumedrapidlywithoutanylargeincreaseinmolecularweight.酯化的结果是单体分子很快地被消耗掉，而分子量却没有多少增加。Fig.3.1illustratesthisphenomenon.Assume,forexample,thateachsquareinFig.3.1arepresentsamoleculeofhydroxyacid.Aftertheinitialdimmermoleculesfrom(b),halfthemonomermoleculeshavebeenconsumedandtheaveragedegreeofpolymerizationDPofpolymericspeciesis2.图3.1说明了这个现象。假定图3.1中的每一个方格代表一个羟基酸分子。产生二聚体分子后(b)，一半的单体分子消耗了，这时平均聚合度(DP)是2。Astrimerandmoredimermoleculesform(c),morethan80%ofthemonomermoleculeshavereacted,butDPisstill2.5.Whenallthemonomermoleculeshavereacted(d),DPis4. (c)中形成三聚体和更多的二聚体，超过80%的单体分子已参加反应，但DP仅仅还是2.5。(d)中所有的单体反应完，DP是4。Buteachpolymermoleculethatformsstillhasreactiveendgroups;hencethepolymerizationreactionwillcontinueinastepwisefashion,witheachesterificationstepbeingidenticalinrateandmechanismtotheinitialesterificationofmonomers.继续进行，其每一步酯化反应的反应速率和反应机理均与初始单体的酯化作用相同。Thus,molecularweightincreasesslowlyevenathighlevelsofmonomerconversion,anditwillcontinuetoincreaseuntiltheviscositybuild-upmakesitmechanicallytoodifficulttoremovewaterofesterificationorforreactiveendgroupstofindeachother.反应的水或端基难以相互反应为止。ItcanalsobeshownthatintheA-A+B-Btypeofpolymerization,anexactstoichiometricbalanceisnecessarytoachievehighmolecularweights.Ifsomemonofunctionalimpurityispresent,itsreactionwilllimitthemolecularweightbyrenderingachainendinactive.些单官能团杂质，由于链的端基失活，其反应将限制分子量。Similarly,high-puritymonomersarenecessaryintheA-Btypeofpolycondensationanditfollowsthathigh-yieldreactionsaretheonlypracticalonesforpolymerformation,sincesidereactionswillupsetthestoichiometricbalance.形成聚合物的实用方法只能是高收率的反应。UNIT4IonicPolymerizationIonicpolymerization,similartoradicalpolymerization,alsohasthemechanismofachainreaction.Thekineticsofionicpolymerizationare,however,considerablydifferentfromthatofradicalpolymerization.由基聚合反应。(1)Theinitiationreactionofionicpolymerizationneedsonlyasmallactivationenergy.Therefore,therateofpolymerizationdependsonlyslightlyonthetemperature.(1)离子聚合的引发反应仅需要很小的活化能。因此，聚合反应的速率与温度关系不Ionicpolymerizationsoccurinmanycaseswithexplosiveviolenceevenattemperature.below50℃(forexample,theanionicpolymerizationofstyreneat–70℃intetrahydrofuran,orthecationicpolymerizationofisobutyleneat–100℃inliquidethylene).在四氢呋喃中反应，异丁烯的阳离子聚合在-100℃在液态乙烯中反应)。Withionicpolymerizationthereisnocompulsorychainterminationthroughrecombinationbecausethegrowingchainscannotreactwitheachother.Chainterminationtakesplaceonlythroughimpurities,orthroughtheadditionofcertaincompoundssuchaswater,alcohols,acids,amines,oroxygen,andingeneralthroughcompoundswhichcanreactwithpolymerizationionsundertheformationofneutralcompoundsorinactiveionicspecies.化合物进行加成而发生，且一般来说(链终止反应)可通过这样的化合物来进行，这种化合物可以和活性聚合物离子进行反应生成中性聚合物或没有聚合活性的离子型聚Iftheinitiatorsareonlypartlydissociated,theinitiationreactionisanequilibriumreaction,wherereactioninonedirectiongivesrisetochaininitiationandintheotherdirectiontochaintermination.在一个方向上进行链引发反应，而在另一个方向上则发生链终止反应。Ingeneralionicpolymerizationcanbeinitiatedthroughacidicorbasiccompounds.通常离子聚合反应能通过酸性或碱性化合物被引发。Forcationicpolymerization,complexesofBF3,AlCl3,TiCl4,andSnCl4withwater,oralcohols,ortertiaryoxoniumsaltshaveshownthemselvestobeparticularlyactive.ThepositiveionsaretheonesthatcausechaininitiationForexample:BFAlClTiClSnCl叔烊盐的络合物活性特别高。正离子产生链引发。例如：However,alsowithHCl,H2SO4,andKHSO4,onecaninitiatecationicpolymerization.Initiatorsforanionicpolymerizationarealkalimetalsandtheirorganiccompounds,suchasphenyllithium,butyllithium,phenylsodium,andtriphenylmethylpotassium,whicharemoreorlessstronglydissociatedindifferentsolvents.但BF3与HCl、H2SO4和KHSO4也可以引发阳离子聚合反应。阴离子聚合反应的引发剂是碱金属和它们的有机金属化合物，例如苯基锂、丁基锂和三苯甲基锂，它们在溶剂中高度离解。TothisgroupbelongalsothesocalledAlfincatalysts,whichareamixtureofsodiumisopropylate,allylsodium,andsodiumchloride.所谓的Alfin催化剂就是属于这一类，这类催化剂是异丙醇钠、烯丙基钠和氯化钠的混合物。WithBFandisobutyleneasthemonomeritwasdemonstratedthatthepolymerizationispossibleonlyinthepresenceoftracesoftracesofwateroralcohol.BF3为引发剂(异丁烯为单体)，在痕量水或乙醇下聚合反应才可以进行。Ifoneeliminatesthetraceofwater,BF3alonedoesnotgiverisetopolymerization.WateroralcoholsarenecessaryinordertoallowtheformationoftheBF3-complexandtheinitiatorcationaccordingtotheabovereactions.However,oneshouldnotdescribe如果消除痕量的水，BF3单独不会引发聚合反应。对于上述反应，水或乙醇对于形ononecanalsopreparecopolymersbyionicpolymerization,forexample,anioniccopolymersofstyreneandbutadiene,orcationiccopolymersofisobutyleneandstyrene,orisobutyleneandvinyethers,etc.与自由基聚合反应一样，通过离子聚合反应也能制备共聚物，例如，苯乙烯-丁二等。Ashasbeendescribedindetailwithradicalpolymerization,onecancharacterizeeachmonomerpairbyso-calledreactivityratiosr1andr2.UNIT5IntroductiontoLivingRadicalPolymerizationTraditionalmethodsoflivingpolymerizationarebasedonionic,coordinationorgrouptransfermechanisms.活性聚合的传统方法是基于离子，配位或基团转移机理。Ideally,themechanismoflivingpolymerizationinvolvesonlyinitiationandpropagationsteps.理论上活性聚合的机理只包括引发和增长反应步骤。Allchainsareinitiatedatthecommencementofpolymerizationandpropagationcontinuesuntilallmonomerisconsumed.Atypeofnoveltechniquesforlivingpolymerization,knownasliving(possiblyuse“controlled”or“mediated”)radicalpolymerization,isdevelopedrecently.最近开发了一种叫做活性自由基聚合的活性聚合新技术。ThefirstdemonstrationoflivingradicalpolymerizationandthecurrentdefinitionoftheprocessescanbeattributedtoSzwarc.Uptonow,severallivingradicalpolymerizationprocesses,includingatomtransferradicalpolymerization(ATRP),reversibleaddition-fragmentationchaintransferpolymerization(RAFT),nitroxide-mediatedpolymerization(NMP),etc.,havebeenreportedoneafteranother.到目前为止，一些活性自由基聚合过程，包括原子转移自由基聚合，可逆加成-断裂链转移聚合，硝基氧介导聚合等聚合过程一个接一个被报道。Themechanismoflivingradicalpolymerizationisquitedifferentnotonlyfromthatofcommonradicalpolymerizationbutalsofromthatoftraditionallivingpolymerization.Itreliesontheintroductionofareagentthatundergoesreversibleterminationwiththepropagatingradicalstherebyconvertingthemtoafollowingdormantform：Thespecificityinthereversibleinitiation-terminationstepisofcriticalimportanceinachievinglivingcharacteristics.这种特殊的可逆引发-终止反应对于获得分子链活性来说具有决定性的重要意义。Thisenablestheactivespeciesconcentrationtobecontrolledandthusallowssuchaconditiontobechosenthatallchainsareabletogrowatasimilarrate(ifnotsimultaneously)throughoutthepolymrization.使得在整个聚合反应过程中(只要没有平行反应)所有的分子链都能够以相同的速度增Thishas,inturn,enabledthesynthesisofpolymerswithcontrolledcomposition,architectureandmolecularweightdistribution.这样就可以合成具有可控组成，结构和分子量分布的聚合物。Theyalsoprovideroutestonarrowdispersityend-functionalpolymers,tohighpurityblockcopolymers,andtostarsandothermorecomplexarchitecture.方法。ThefirststeptowardslivingradicalpolymerizationwastakenbyOstuandhisleaguesinIn1985,thiswastakenonestepfurtherwiththedevelopmentbySolomonetal.ofnitroxide-mediatedpolymerization(NMP).Thisworkwasfirstreportedinthepatentliteratureandinconferencepapersbutwasnotwidelyrecognizeduntil1993whenGeorgesetal.appliedthemethodinthesynthesisofnarrowpolydispersitypolystyrene.报道，但是直到1993年Georges等把这种方法应用在窄分子量分布聚苯乙烯之后，才得以广泛认知。ThescopeofNMPhasbeengreatlyexpendedandnew,moreversatile,methodshaveappeared.NMP的领域已经得到很大的延展，出现了新的更多样化的方法。Themostnotablemethodsareatomtransferradicalpolymerization(ATRP)andpolymerizationwithreversibleadditionfragmentation(RAFT).最引人注目的方法是原子转移自由基聚合和可逆加成断裂聚合。Upto2000,thisareaalreadyaccountedforonethirdofallpapersinthefieldofradicalpolymerization,asshowninFig.5.1.Naturally,therapidgrowthofthenumberofthepapersinthefieldsince1995oughttobealmosttotallyattributabletodevelopmentinthisarea.。ghtanditsDistributionsofPolymersThemolecularweightofapolymerisofprimeimportanceinitssynthesisandapplication.对聚合物的合成和应用而言，聚合物的分子量是最重要的。Theinterestingandusefulmechanicalpropertieswhichareuniquelyassociatedwithpolymericmaterialsareaconsequenceoftheirhighmolecularweight.些性能是聚合物的高分子量带来的。聚合物材料的高分子量带来了令人感兴趣的和具用价值的力学性能。Mostimportantmechanicalpropertiesdependonandvaryconsiderablywithmolecularweight.最重要的力学性能取决于分子量，而且随着分子量变化而发生很大的变化。Thus,strengthofpolymerdoesnotbegintodevelopuntilaminimummolecularweightofabout5000~10000isachieved.因此,直到最小分于量增大到大约5000~10000以后,聚合物的强度才开始显示Abovethatsize,thereisarapidincreaseinthemechanicalperformanceofpolymersastheirmolecularweightincreases;theeffectlevelsoffatstillhighermolecularweights.Leveloff…达到平衡，变平缓，趋缓分子量大于这个值的时候，随着分子量的增加，聚合物的机械性能快速增加;达到更高的分子量的时候，这种效应才变平缓。Inmostinstances,thereissomemolecularweightrangeinwhichagivenpolymerpropertywillbeoptimumforaparticularapplication.Thecontrolofmolecularweightisessentialforthepracticalapplicationofapolymerizationprocess.合物的分子量。Whenonespeaksofthemolecularweightofapolymer,onemeanssomethingquitedifferentfromthatwhichappliestosmall-sizedcompounds.当人们谈到聚合物分子量的时候，他所指的是和(适用于)低分子化合物的分子量完全不同的另一回事。Polymersdifferfromthesmallsizedcompoundsinthattheyarepolydisperseorheterogeneousinmolecularweight.聚合物与小分子量化合物的不同在于聚合物的分子量是多分散性的或不均匀的。Evenifapolymerissynthesizedfreefromcontaminantsandimpurities,itisstillnotapuresubstanceintheusuallyacceptedsense.仍然Polymers,intheirpurestform,aremixtureofmoleculesofdifferentmolecularweights.最纯净的聚合物是具有不同分子量的分子的混合物。Thereasonforthepolydispersityofpolymersliesinthestatisticalvariationspresentinthepolymerizationprocesses.聚合物多分散性在于聚合过程中展现的统计变化。Whenonediscussesthemolecularweightofapolymer,oneisactuallyinvolvedwithitsaveragemolecularweight.讨论聚合物的分子量，准确的含义是平均分子量。Boththeaveragemolecularweightandtheexactdistributionofdifferentmolecularweightswithinapolymerarerequiredinordertofullycharacterizeit.情况。Thecontrolofmolecularweightandmolecularweightdistribution(MWD)isoftenusedtoobtainandimprovecertaindesiredphysicalpropertiesinapolymerproduct.Variousmethodsareavailablefortheexperimentalmeasurementoftheaveragemolecularweightofapolymersample.在聚合物样品平均分子量的实验测试中有许多方法可以利用。Theseincludemethodsbasedoncolligativeproperties,lightscattering,viscosity,ultracentrifugation,andsedimentation.这些方法基于依数性，光散射，粘度法，超速离心分离，沉降法。Thevariousmethodsdonotyieldthesameaveragemolecularweight.不同的方法得到不同的平均分子量。Differentaveragemolecularweightsareobtainedbecausethepropertiesbeingmeasuredarebiaseddifferenttowardthedifferentsizedpolymermoleculesinapolymersample.(对同一聚合物)得到了不同的平均分子量，因为所测得的性质对试样中不同尺寸的聚合物分子有不同的偏差。Somemethodsarebiasedtowardthelargersizedpolymermolecules,whileothermethodsarebiasedtowardthesmallersizedmolecules.一些方法对较大尺寸的聚合物分子有偏差(倾向性)，而另外一些方法则对较小尺寸的聚合物分子有偏差(倾向性)。Theresultisthattheaveragemolecularweightsobtainedarecorrespondinglybiasedtowardthelargerorsmallersizedmolecules.所获得的平均分子量分别对较大的或较小的分子有(偏差)倾向性。Themostimportantaveragemolecularweightswhicharedeterminedarethenumber-averagemolecularweightMn,theweight-averagemolecularweightMwandtheviscosityaveragemolecularweightMv.。Inadditiontothedifferentaveragemolecularweightsofapolymersample,itisfrequentlydesirableandnecessarytoknowtheexactdistributionofmolecularweights.除聚合物样品的不同的平均分子量外，经常需要知道确切的分子量分布。Avarietyofdifferentfractionationmethodsareusedtodeterminethemolecularweightdistributionofapolymersample.各种各样的不同的分级方法被用来确定聚合物样品的分子量分布。Thesearebasedonfractionationofapolymersampleusingproperties,suchassolubilityandpermeability,whichvarywithmolecularweight.子量变化而变化。UNITUNIT7PolymerSolutionDissolvingapolymerisaslowprocessthatoccursintwostages.溶解高分子需要一个缓慢的过程，这个过程分两步发生。First,solventmoleculesslowlydiffuseintothepolymertoproduceaswollengel.溶剂分子缓慢地扩散到高分子中产生溶胀凝胶。Thismaybeallthathappensif，forexample，thepolymer-polymerintermolecularforcesarehighbecauseofcrosslinking，crystallinity·orstronghydrogenbonding.例如,如果因交联，结晶和很强的氢键而形成很大的分子间力，(聚合物的溶解过程)有可能就只停留在这一阶段。Butiftheseforcescanbeovercomebytheintroductionofstrongpolymer-solventinteractions,thesecondstageofsolutioncantakeplace.段就会发生。Herethegelgraduallydisintegratesintoatruesolution.Onlythisstagecanbemateriallyspeededbyagitation.过搅拌得到明显促进。Evenso,thesolutionprocesscanbequiteslow(daysorweeks)formaterialsofveryhighmolecularweight.虽然如此，对高分子量的材料而言，溶解过程是相当缓慢的(几天或几个星期)。Solubilityrelationsinpolymersystemsaremorecomplexthanthoseamonglowmolecular-weightcompounds,becauseofthesizedifferencesbetweenpolymerandsolventmolecules,theviscosityofthesystem,andtheeffectsofthetextureandmolecularweightofthepolymer.态结构的影响等原因，高分子体系的溶解性关系比低分子量化合物要复杂得多。Inturn，thepresenceorabsenceofsolubilityasconditions(suchasthenatureofthesolvent，orthetemperature)arevariedcangivemuchinformationaboutthepolymer.当条件(溶剂的性质或温度)变化的时候，有无溶解性又可提供出许多关于这种聚合物的信息。Asspecifiedintheliterature，thearrangementsofthepolymerchaindifferingbyreasonofrotationsaboutsinglebandsaretermedconformations.。tionapolymermoleculeisarandomlycoilingmassmostofwhoseconformationsoccupy[‘okjupai]manytimesthevolumeofitssegmentsalone.大部分构象占链段分子自身体积的许多倍。Theaveragedensityofsegmentswithinadissolvedpolymermoleculeisof10-4~10-5g/cm3.溶解聚合物分子里的平均链段密度是10-4~10-5g/cm3Thesizeofthemolecularcoilisverymuchinfluencedbythepolymer-solventinteractionforces.聚合物-溶剂之间的作用力对分子线团尺寸有很大的影响。Inathermodynamically“good”solvent,wherepolymer-solventcontactsarehighlyfavored,thecoilsarerelativelyextended.在热力学上的好溶剂中，聚合物-溶剂作用较强，线团是相对伸展的。Inapoor”solventtheyarerelativelycontracted.而在不良溶剂中，线团则是相对收缩的。Itisthepurposetodescribetheconformationalpropertiesofbothidealandrealpolymerchains.使用上述方法的目的是描述理想的和真实的聚合物链构象。Theimportanceoftherandom-coilnatureofthedissolved,molten,amorphous,andglassystatesofhighpolymerscannotbeoveremphasized.Manyimportantphysicalaswellasthermodynamicpropertiesofhighpolymersresultfromthischaracteristicstructuralfeature.高分子的许多重要的物理及热力学性质都是这个结构特征引起的。Therandomcoil(Fig.7.1)arisesfromtherelativefreedomofrotationassociatedwiththechainbondsofmostpolymersandtheformidablylargenumberofconformationsaccessibletothemolecule.无规线团(图7.1)一方面是由于聚合物链上的键自由旋转而产生的，另一方面是由于(聚合物)分子(链)可达到巨大的构象数而产生的。Fig.Tab.Oneoftheseconformations,thefullyextendedchainhasspecialinterestbecauseitslength,thecontourlengthofthechain,canbecalculatedinastraightforwardway.长度可以直接地计算出来。Inallothercasesthesizeoftherandomcoilmustbeexpressedintermsofstatisticalparameterssuchastheroot-mean-squaredistancebetweenitsends,(r2)1/2,oritsradiusofgyration,theroot-mean-squaredistanceoftheelementsofthechainfromitscenterofgravity,(s2)1/2.在所有其他的场合，无规线团的尺寸必须用统计参数来表示，如链末端之间距离的均方根，(r2)1/2或回旋半径，从分子重心(质心)到链节距离的均方根(s2)1/2Forlinearpolymersthatarenotappreciablyextendedbeyondtheirmostprobableshape,themean-squareend-to-enddistanceandthesquareoftheradiusofgyrationaresimplyrel