高分子材料工程專業(yè)英語翻譯

專業(yè)專業(yè).專注學(xué)習(xí)參考學(xué)習(xí)參考Unit1Whatarepolymers?Whatarepolymers?Foronething,theyarecomplexandgiantmoleculesandaredifferentfromlowmolecularweightcompoundslike,say,commonsalt.什么是高聚物？首先，他們是合成物和大分子，而且不同于低分子化合物，譬如說普通的鹽。Tocontrastthedifference,themolecularweightofcommonsaltisonly58.5,whilethatofapolymercanbeashighasseveralhundredthousand,evenmorethanthousandthousands.與低分子化合物不同的是，普通鹽的分子量僅僅是58.5，而高聚物的分子量高于105，甚至大于106。Thesebigmoleculesor‘macro-molecules’aremadeupofmuchsmallermolecules,canbeofoneormorechemicalcompounds.這些大分子或“高分子”由許多小分子組成。小分子相互結(jié)合形成大分子，大分子能夠是一種或多種化合物。Toillustrate,imaginethatasetofringshasthesamesizeandismadeofthesamematerial.Whenthesethingsareinterlinked,thechainformedcanbeconsideredasrepresentingapolymerfrommoleculesofthesamecompound.舉例說明，想象一組大小相同并由相同的材料制成的環(huán) 。當(dāng)這些環(huán)相互連接起來，可以把形成的鏈看成是具有同種化合物組成的高聚物。Alternatively,individualringscouldbeofdifferentsizesandmaterials,andinterlinkedtorepresentapolymerfrommoleculesofdifferentcompounds.另一方面，環(huán)可以大小不同、材料不同,物。Thisinterlinkingofmanyunitshasgiventhepolymeritsname,polymeaning‘many’andmermeaning‘part’(inGreek).，poly意味著“、聚、重復(fù)”，mer意味著“鏈節(jié)、基體”（希臘語中）。Asanexample,agaseouscompoundcalledbutadiene,withamolecularweightof54,combinesnearly4000timesandgivesapolymerknownaspolybutadiene(asyntheticrubber)withabout200000molecularweight.例如：氣態(tài)化合物丁二烯的分子量為 54，連接4000次可得到分子量大約為200000的聚丁二烯（合成橡膠）高聚物。Thelowmolecularweightcompoundsfromwhichthepolymersformareknownasmonomers.Thepictureissimplyasfollows:形成高聚物的低分子化合物稱為單體。下面簡單地描述一下形成過程：butadiene+butadiene+???+butadiene--→polybutadiene(4000time)丁二烯＋丁二烯＋…＋丁二烯——→聚丁二烯（4000次）Onecanthusseehowasubstance(monomer)withassmallamoleculeweightas54growtobecomeagiantmolecule(polymer)of(54×4000≈)200000molecularweight.能夠知道分子量僅為54的小分子物質(zhì)（單體）如何逐漸形成分子量為200000的大分子（高聚物）。Itisessentiallythe“giantness”ofthesize ofthepolymermoleculethatmakesitsbehavior(differentfromthatofacommonlyknownchemicalcompoundsuchasbenzene.)實(shí)質(zhì)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這樣的一般化合物（的性能）Solidbenzene,forinstance,meltstobecomeliquidbenzeneat5.5℃and,onfurtherheating,boilsintogaseousbenzene.例如固態(tài)苯在5.5℃熔融成液態(tài)苯，進(jìn)一步加熱，煮沸成氣態(tài)苯。Asagainstthiswell-definedbehaviorofasimplechemicalcompound,apolymerlikepolyethylenedoesnotmeltsharplyatoneparticulartemperatureintocleanliquid.與這類簡單化合物明確的行為相比，像聚乙烯這樣的聚合物不能在某一特定的溫度快速地熔融成純凈的液體。Instead,itbecomesincreasinglysofterand,ultimately,turnsintoaveryviscous,tackymoltenmass.Furtherheatingofthishot,viscous,moltenpolymerdoesconvertitintovariousgasesbutitisnolongerpolyethylene.(Fig.1.1).而聚合物變得越來越軟，最終變成十分粘稠的聚合物熔融體。將這種熱而粘稠的聚合物熔融體進(jìn)一步加熱，它會(huì)轉(zhuǎn)變成不同氣體，但它不再是聚乙烯（如圖1.1）Anotherstrikingdifferencewithrespecttothebehaviorofapolymerandthatofalowmolecularweightcompoundconcernsthedissolutionprocess.聚合物行為和低分子量化合物另一不同的行為為溶解過程。Letustake,forexample,sodiumchlorideandadditslowlyto fixedquantityofwater.Thesalt,whichrepresentsalowmolecularweightcompound,dissolvesinwateruptoapoint(calledsaturationpoint)but,thereafter,anyfurtherquantityaddeddoesnotgointosolutionbutsettlesatthebottomandjustremainsthereassolid.例如，將氯化鈉慢慢地添加到定量的水中。鹽作為一種低分子量化合物，在水中溶解直到某一點(diǎn)（叫飽和點(diǎn)），但進(jìn)一步添加,鹽不進(jìn)入溶液中卻沉到底部而保持原有的固體狀態(tài)Theviscosityofthesaturatedsaltsolutionisnotverymuchdifferentfromthatofwater.Butifwetakeapolymerinstead,say,polyvinylalcohol,andaddittoafixedquantityofwater,thepolymerdoesnotgointosolutionimmediately.飽和鹽溶液的粘度與水的粘度接近.但是，如果我們用聚合物，如聚乙烯醇添加到定量水中，聚合物不是馬上進(jìn)入到溶液中。Theglobulesofpolyvinylalcoholfirstabsorbwater,swellandgetdistortedinshapeandafteralongtimegointosolution.聚乙烯醇顆粒首先吸水溶脹，發(fā)生變形，經(jīng)過很長時(shí)間后，（聚乙烯醇分子）進(jìn)入到溶液中。Also,wecanaddaverylargequantityofthepolymertothesamequantityofwaterwithoutthesaturationpointeverbeingreached.同樣地，我們可以將大量的聚合物加入到同樣量的水中，不存在飽和點(diǎn)。Asmoreandmorequantityofpolymerisaddedtowater,thetimetakenforthedissolutionofthepolymerobviouslyincreasesandthemixultimatelyassumesasoft,dough-likeconsistency.將越來越多的聚合物加入水中，認(rèn)為聚合物溶解的時(shí)間明顯地增加，最終呈現(xiàn)柔軟像面團(tuán)一樣粘稠的混合物。Anotherpeculiarityisthat,inwater,polyvinylalcoholneverretainsitsoriginalpowderynature[astheexcesssodiumchloridedoes][inasaturatedsaltsolution].另一個(gè)特點(diǎn)是，在水中聚乙烯醇不會(huì)像過量的氯化鈉在飽和鹽溶液中那樣能保持其初始的粉末狀態(tài)。Inconclusion,wecansaythat(1)thelongtimetakenbypolyvinylalcoholfordissolution,(2)theabsenceofasaturationpoint,and(3)theincreaseintheviscosityareallcharacteristicsofatypicalpolymerbeingdissolvedinasolventandthese characteristicsareattributedmainlytothelargemolecularsizeofthepolymer.總之，我們可以講（1）聚乙烯醇的溶解需要很長時(shí)間，（2），（3）粘度的增加是聚合物溶于溶液中的典型特性，這些特性主要?dú)w因于聚合物大分子的尺寸。ThebehaviorofalowmolecularweightcompoundandthatofapolymerondissolutionareillustratedinFig.1.2.Unit2ChainPolymerizationManyolefinicandvinylunsaturatedcompoundsareabletoformchain-likemacromoleculesthrougheliminationofthedoublebond,aphenomenonfirstrecognizedbyStaudinger.Diolefinspolymerizeinthesamemanner,however,onlyoneofthetwodoublebondsiseliminated.Staudinger首先發(fā)現(xiàn)許多烯烴和不飽和烯烴通過打開雙鍵可以形成鏈?zhǔn)酱蠓肿?。二烯烴以同樣的方式聚合，但僅消除兩個(gè)雙鍵中的一個(gè)。Suchreactionsoccurthroughtheinitialadditionofamonomermoleculetoaninitiatorradicaloraninitiatorion,bywhichtheactivestateistransferredfromtheinitiatortotheaddedmonomer.這類反應(yīng)是通過單體分子首先加成到引發(fā)劑自由基或引發(fā)劑離子上而進(jìn)行的 ，靠。Inthesamewaybymeansofachainreaction,onemonomermoleculeaftertheotherisadded(2000~20000monomerspersecond)untiltheactivestateisterminatedthroughadifferenttypeofreaction.單體分子通過鏈?zhǔn)椒磻?yīng)以同樣的方式一個(gè)接一個(gè)地加上（每秒2000～20000個(gè)單體）直到活性中心通過不同的反應(yīng)方式終止。Thepolymerizationisachainreactionintwoways:becauseofthereactionkineticandbecauseasareactionproductoneobtainsachainmolecule.Thelengthofthechainmoleculeisproportionaltothekineticchainlength.聚合反應(yīng)成為鏈?zhǔn)椒磻?yīng)的兩種原因：反應(yīng)動(dòng)力學(xué)和作為鏈?zhǔn)椒磻?yīng)產(chǎn)物分子。鏈分子的長度與動(dòng)力學(xué)鏈長成正比。Onecansummarizetheprocessasfollow(R.isequaltotheinitiatorradical):鏈?zhǔn)椒磻?yīng)可以概括為以下過程（R·相當(dāng)與引發(fā)劑自由基）：略O(shè)nethusobtainspolyvinylchloridefromvinylchloride,orpolystyrenefromstyrene,orpolyethylenefromethylene,etc.因而通過上述過程由氯乙烯得到聚氯乙烯，或由苯乙烯獲得聚苯乙烯，或乙烯獲得聚乙烯，等等。Thelengthofthechainmolecules,measuredbymeansofthedegreeofpolymerization,canbevariedoveralargerangethroughselectionofsuitablereactionconditions.分子鏈長通過聚合度測量，可以通過選擇適宜的反應(yīng)條件大為改變Usually,withcommerciallypreparedandutilizedpolymers,thedegreeofpolymerizationliesintherangeof1000to5000,butinmanycasesitcanbebelow500andover10000.商業(yè)制備和使用的聚合物，聚合度通常在1000～5000范圍內(nèi)，但在許多情況下50010000。Thisshouldnotbeinterpretedtomeanthatallmoleculesofacertainpolymericmaterialconsistof500,or1000,or5000monomerunits.Inalmostallcases,thepolymericmaterialconsistsofamixtureofpolymermoleculesofdifferentdegreesofpolymerization.這不應(yīng)該把聚合物材料所有的分子理解為由500，或1000，或5000個(gè)單體單元組成。。Polymerization,achainreaction,occursaccordingtothesamemechanismasthewell-knownchlorine-hydrogenreactionandthedecompositionofphosegene.鏈?zhǔn)骄酆戏磻?yīng)的機(jī)理與眾所周知的氯（氣）-氫（氣）反應(yīng)和光氣的分解機(jī)理相同。Theinitiationreaction,whichistheactivationprocessofthedoublebond,canbebroughtaboutbyheating,irradiation,ultrasonics,orinitiators.Theinitiationofthechainreactioncanbeobservedmostclearlywithradicalorionicinitiators.通過雙鍵活化的引發(fā)劑反應(yīng)，可以通過熱、輻射、超聲波或引發(fā)劑產(chǎn)生?？梢院芮宄剡M(jìn)行研究用自由基型或離子型引發(fā)劑引發(fā)的鏈?zhǔn)椒磻?yīng)。Theseareenergy-richcompoundswhichcanaddsuitableunsaturatedcompounds(monomers)andmaintaintheactivatedradicalorionicstatesothatfurthermonomermoleculescanbeaddedinthesamemanner.這些是高能態(tài)的化合物，它們能夠加成不飽和化合物（單體）并保持自由基或離子活性中心以致單體可以以同樣的方式進(jìn)一步加成。Fortheindividualstepsofthegrowthreactiononeneedsonlyarelativelysmallactivationenergyandthereforethroughasingleactivationstep(theactualinitiationreaction)alargenumberofolefinmoleculesareconverted,asisimpliedbytheterm“chainreaction”.對于增長反應(yīng)的各個(gè)步驟，每一步僅需要相當(dāng)少的活化能，因此通過一步簡單的活化反應(yīng)（即引發(fā)反應(yīng)）即可將許多烯類單體分子轉(zhuǎn)化成聚合物，這正如連鎖反應(yīng)這個(gè)術(shù)語的內(nèi)涵那樣。Becauseverysmallamountsoftheinitiatorbringabouttheformationofalargeamountofpolymericmaterial(1:1000to1:1000),itispossibletoregardpolymerizationfromasuperficialpointofviewasacatalyticreaction.因?yàn)樯倭康囊l(fā)劑引發(fā)形成大量的聚合物原料（1：1000～1：10000），從表面上看聚合反應(yīng)被看成是催化反應(yīng)。Forthisreason,theinitiatorsusedinpolymerizationreactionsareoftendesignatedaspolymerizationcatalysts,eventhough,inthestrictestsense,theyarenottruecatalystsbecausethepolymerizationinitiatorentersintothereactionasarealpartnerandcanbefoundchemicallyboundinthereactionproduct,i.e.,thepolymer.由于這個(gè)原因，通常把聚合反應(yīng)的引發(fā)劑看作是聚合反應(yīng)的引發(fā)劑。但因?yàn)榫酆戏磻?yīng)的催化劑進(jìn)入到反應(yīng)內(nèi)部而成為一部分，同時(shí)可以在反應(yīng)產(chǎn)物，既聚合物的末端發(fā)現(xiàn)催化劑，所以嚴(yán)格地講它們不是真正意義上的催化劑，Inadditiontotheionicandradicalinitiatorstherearenowmetalcomplexinitiators(whichcanbeobtained,forexample,bythereactionoftitaniumtetrachlorideortitaniumtrichloridewithaluminumalkyls),whichplayanimportantroleinpolymerizationreactions(Zieglercatalysts),Themechanismoftheircatalyticactionisnotyetcompletelyclear.除離子引發(fā)劑和自由基引發(fā)劑外，還有金屬絡(luò)合物引發(fā)劑（可以通過四氯化鈦或三氯化鈦與烷基鋁的反應(yīng)得到）。它們在聚合反應(yīng)中起到了重要作用（齊格納引發(fā)劑）。它們催化活動(dòng)的機(jī)理還不是十分清楚。UNIT3 Step-GrowthpolymerizationManydifferentchemicalreactionsmaybeusedtosynthesizepolymericmaterialsbystep-growthpolymerization.Theseincludeesterification,amidation,theformationofurethanes,aromaticsubstitution,etc.通過逐步聚合可用許多不同的化學(xué)反應(yīng)來合成聚合材料。這些反應(yīng)包括酯化、酰胺化、氨基甲酸酯、芳香族取代物的形成等。Polymerizationproceedsbythereactionsbetweentwodifferentfunctionalgroups,e.g.,hydroxylandcarboxylgroups,orisocyanateandhydroxylgroups.通過在兩種不同的官能團(tuán)，如，羥基和羧基，或異氰酸酯和羥基之間可發(fā)生聚合反應(yīng)。Allstep-growthpolymerizationfallintotwogroupsdependingonthetypeofmonomer(s)employed.Thefirstinvolvestwodifferentpolyfunctionalmonomersinwhicheachmonomerpossessesonlyonetypeoffunctionalgroup.所有的逐步聚合反應(yīng)根據(jù)所使用單體的類型可分為兩類。第一類涉及兩種不同的官能團(tuán)單體，每一種單體僅具有一種官能團(tuán)。Apolyfunctionalmonomerisonewithtwoormorefunctionalgroupspermolecule.Thesecondinvolvesasinglemonomercontainingbothtypesoffunctionalgroups.一種多官能團(tuán)單體每個(gè)分子有兩個(gè)或多個(gè)官能團(tuán)。第二類涉及含有兩類官能團(tuán)的單個(gè)單體。Thesynthesisofpolyamidesillustratesbothgroupsofpolymerizationreactions. Thus,polyamidescanbeobtainedfromthereactionofdiamineswithdiacidsorfromthereactionofaminoacidswiththemselves.聚酰胺的合成說明了兩類聚合反應(yīng)。因此聚酰胺可以由二元胺和二元酸的反應(yīng)或氨基酸之間的反應(yīng)得到。Thetwogroupsofreactionscanberepresentedinageneralmannerbytheequationsasfollows兩種官能團(tuán)之間的反應(yīng)一般來說可以通過下列反應(yīng)式表示Reaction(3.1)illustratestheformer,while(3.2)isofthelattertype.反應(yīng)（3.1）說明前一種形，而反（3.2）具有后一種形。Polyesterification, whether between diol and dibasic acid intermolecularlybetweenhydroxyacidmolecules,isanexampleofastep-growthpolymerizationprocess.聚酯化反應(yīng)是逐步聚合反應(yīng)過程的一個(gè)例子。反應(yīng)可能在二元酸和二元醇之間或羥基酸分子間進(jìn)行。Theesterificationreactionoccursanywhereinthemonomermatrixwheretwomonomermoleculescollide,andoncetheesterhasformed,it,too,canreactfurtherbyvirtueofitsstill-reactivehydroxylorcarboxylgroups.酯化反應(yīng)出現(xiàn)在單體本體中兩個(gè)單體分子相碰撞的位置，且酯一旦形成，依靠酯上仍有活性的羥基或羧基還可以進(jìn)一步進(jìn)行反應(yīng)。Theneteffectofthisisthatmonomermoleculesareconsumedrapidlywithoutanylargeincreaseinmolecularweight.酯化的結(jié)果是單體分子很快地被消耗掉，而分子量卻沒有多少增加。Fig.3.1illustratesthisphenomenon.Assume,forexample,thateachsquareinFig.3.1arepresentsamoleculeofhydroxyacid.Aftertheinitialdimmermoleculesfrom(b),halfthemonomermoleculeshavebeenconsumedandtheaveragedegreeofpolymerization(DP)ofpolymericspeciesis2.3.1。3.1。，（DP）2。Astrimerandmoredimermoleculesform(c),morethan80%ofthemonomermoleculeshavereacted,butDPisstill2.5.Whenallthemonomermoleculeshavereacted(d),DPis4.（c）中形成三聚體和更多的二聚體，超過80%的單體分子已參加反應(yīng)，但DP僅僅還是2.5。（d）中所有的單體反應(yīng)完，DP是4。Buteachpolymermoleculethatformsstillhasreactiveendgroups;hencethepolymerizationreactionwillcontinueinastepwisefashion,witheachesterificationstepbeingidenticalinrateandmechanismtotheinitialesterificationofmonomers.但形成的每一種聚合物分子還有反應(yīng)活性的端基；因此，聚合反應(yīng)將以逐步的方式繼續(xù)進(jìn)行，其每一步酯化反應(yīng)的反應(yīng)速率和反應(yīng)機(jī)理均與初始單體的酯化作用相同。Thus,molecularweightincreasesslowlyevenathighlevelsofmonomerconversion,anditwillcontinuetoincreaseuntiltheviscositybuild-upmakesitmechanicallytoodifficulttoremovewaterofesterificationorforreactiveendgroupstofindeachother.這樣，分子量在高單體轉(zhuǎn)化率下緩慢增加，繼續(xù)增加直到粘度增加到難以除去酯化反應(yīng)的水或端基難以相互反應(yīng)為止。ItcanalsobeshownthatintheA-A+B-Btypeofpolymerization,anexactstoichiometricbalanceisnecessarytoachievehighmolecularweights.Ifsomemonofunctionalimpurityispresent,itsreactionwilllimitthemolecularweightbyrenderingachainendinactive.在A-A+B-B的聚合反應(yīng)中，精確的定量配比是獲得高分子量所必需的。假如存在一些單官能團(tuán)雜質(zhì)，由于鏈的端基失活，其反應(yīng)將限制分子量。Similarly,high-puritymonomersarenecessary intheA-Btypeofpolycondensationanditfollowsthathigh-yieldreactionsaretheonlypracticalonesforpolymerformation,sincesidereactionswillupsetthestoichiometricbalance.同樣，在A-B類的縮聚反應(yīng)中高純度的單體是必要的。比，。UNIT4 IonicPolymerizationIonicpolymerization,similartoradicalpolymerization,alsohasthemechanismofachainreaction.Thekineticsofionicpolymerizationare,however,considerablydifferentfromthatofradicalpolymerization.離子聚合反應(yīng)，與自由基聚合反應(yīng)相似，也是鏈反應(yīng)機(jī)理。但離子聚合的動(dòng)力學(xué)明顯地不同于自由基聚合反應(yīng)。(1)Theinitiationreactionofionicpolymerizationneedsonlyasmallactivationenergy.Therefore,therateofpolymerizationdependsonlyslightlyonthetemperature.(1)離子聚合的引發(fā)反應(yīng)僅需要很小的活化能。因此，聚合反應(yīng)的速率與溫度關(guān)系不大。Ionicpolymerizationsoccurinmanycaseswithexplosiveviolenceevenattemperature.below50℃(forexample,theanionicpolymerizationofstyreneat–70℃intetrahydrofuran,orthecationicpolymerizationofisobutyleneat–100℃inliquidethylene).在許多情況甚至低于 50℃下離子聚合反應(yīng)劇烈（例如，苯乙烯的陰離子聚合在-70℃在四氫呋喃中反應(yīng)，異丁烯的陽離子聚合在-100℃在液態(tài)乙烯中反應(yīng)）。Withionicpolymerizationthereisnocompulsorychainterminationthroughrecombination,becausethegrowingchainscannotreactwitheachother.對于離子聚合來說，因?yàn)樯L鏈之間不能發(fā)生反應(yīng)，不存在通過再結(jié)合反應(yīng)而進(jìn)行的強(qiáng)迫鏈終止。Chainterminationtakesplaceonlythroughimpurities,orthroughtheadditionofcertaincompoundssuchaswater,alcohols,acids,amines,oroxygen,andingeneralthroughcompoundswhichcanreactwithpolymerizationionsundertheformationofneutralcompoundsorinactiveionicspecies.鏈終止反應(yīng)僅僅通過雜質(zhì)而發(fā)生，或者說通過和某些像水、醇、酸、胺或氧這樣的化合物進(jìn)行加成而發(fā)生，且一般來說（鏈終止反應(yīng)）可通過這樣的化合物來進(jìn)行，這種化合物可以和活性聚合物離子進(jìn)行反應(yīng)生成中性聚合物或沒有聚合活性的離子型聚合物。Iftheinitiatorsareonlypartlydissociated,theinitiationreactionisanequilibriumreaction,wherereactioninonedirectiongivesrisetochaininitiationandintheotherdirectiontochaintermination.如果引發(fā)劑僅僅部分地離解，引發(fā)反應(yīng)即為一個(gè)平衡反應(yīng)，在出現(xiàn)平衡反應(yīng)的場合，在一個(gè)方向上進(jìn)行鏈引發(fā)反應(yīng)，而在另一個(gè)方向上則發(fā)生鏈終止反應(yīng)。Ingeneralionicpolymerizationcanbeinitiatedthroughacidicorbasiccompounds.通常離子聚合反應(yīng)能通過酸性或堿性化合物被引發(fā)。Forcationicpolymerization,complexesofBF3,AlCl3,TiCl4,andSnCl4withwater,oralcohols,ortertiaryoxoniumsaltshaveshownthemselvestobeparticularlyactive.Thepositiveionsaretheonesthatcausechaininitiation.Forexample:對于陽離子聚合反應(yīng)來說，BF3,AlCl3,TiCl4和SnCl4與水、或乙醇，或叔烊鹽的絡(luò)合物活性特別高。正離子產(chǎn)生鏈引發(fā)。例如：However,alsowithHCl,H2SO4,andKHSO4,onecaninitiatecationicpolymerization.Initiatorsforanionicpolymerizationarealkalimetalsandtheirorganiccompounds,suchasphenyllithium,butyllithium,phenylsodium,andtriphenylmethylpotassium,whicharemoreorlessstronglydissociatedindifferentsolvents.但BF3與HCl、H2SO4和KHSO4陰離子聚合反應(yīng)的引發(fā)劑是堿金屬和它們的有機(jī)金屬化合物，例如苯基鋰、丁基鋰和三苯甲基鋰，它。TothisgroupbelongalsothesocalledAlfincatalysts,whichareamixtureofsodiumisopropylate,allylsodium,andsodiumchloride.所謂的Alfin催化劑就是屬于這一類，這類催化劑是異丙醇鈉、烯丙基鈉和氯化鈉的混合物。WithBF3(andisobutyleneasthemonomer),itwasdemonstratedthatthepolymerizationispossibleonlyinthepresenceoftracesoftracesofwateroralcohol.BF3為引發(fā)劑（異丁烯為單體），在痕量水或乙醇下聚合反應(yīng)才可以進(jìn)行。Ifoneeliminatesthetraceofwater,BF3alonedoesnotgiverisetopolymerization.WateroralcoholsarenecessaryinordertoallowtheformationoftheBF3-complexandtheinitiatorcationaccordingtotheabovereactions.However,oneshouldnotdescribethewaterorthealcoholasa“cocatalyst”.，BF3。，BF3-?！?。Justasbyradicalpolymerization,onecanalsopreparecopolymersbyionicpolymerization,forexample,anioniccopolymersofstyreneandbutadiene,orcationiccopolymersofisobutyleneandstyrene,orisobutyleneandvinyethers,etc.與自由基聚合反應(yīng)一樣，通過離子聚合反應(yīng)也能制備共聚物，例如，苯乙烯-丁二烯陰離子共聚物，或異丁烯-苯乙烯陽離子共聚物，或異丁烯-乙烯基醚共聚物，等等。Ashasbeendescribedindetailwithradicalpolymerization,onecancharacterizeeachmonomerpairbyso-calledreactivityratiosr1andr2.，r1r2。UNIT5 IntroductiontoLivingRadicalPolymerizationTraditional methods of living polymerization are based on coordinationorgrouptransfermechanisms.活性聚合的傳統(tǒng)方法是基于離子，配位或基團(tuán)轉(zhuǎn)移機(jī)理。Ideally,themechanismoflivingpolymerizationinvolvesonlyinitiationandpropagationsteps.理論上活性聚合的機(jī)理只包括引發(fā)和增長反應(yīng)步驟。Allchainsareinitiatedatthecommencementofpolymerizationandpropagationcontinuesuntilallmonomerisconsumed.在聚合反應(yīng)初期所有的鏈都被引發(fā)，然后增長反應(yīng)繼續(xù)下去直到所有的單體都被消耗殆盡。Atypeofnoveltechniquesforlivingpolymerization,knownasliving(possiblyuse“controlled”or“mediated”)radicalpolymerization,isdevelopedrecently.最近開發(fā)了一種叫做活性自由基聚合的活性聚合新技術(shù)。ThefirstdemonstrationoflivingradicalpolymerizationandthecurrentdefinitionoftheprocessescanbeattributedtoSzwarc.第一個(gè)活性自由基聚合的證實(shí)及目前對這一過程的解釋或定義 ，應(yīng)該歸功Szwarc。Uptonow,severallivingradicalpolymerizationprocesses,includingatomtransferradicalpolymerization(ATRP),reversibleaddition-fragmentationchaintransferpolymerization(RAFT),nitroxide-mediatedpolymerization(NMP),etc.,havebeenreportedoneafteranother.到目前為止，一些活性自由基聚合過程，包括原子轉(zhuǎn)移自由基聚合，可逆加成-斷裂鏈轉(zhuǎn)移聚合，硝基氧介導(dǎo)聚合等聚合過程一個(gè)接一個(gè)被報(bào)道。Themechanismoflivingradicalpolymerizationisquitedifferentnotonlyfromthatofcommonradicalpolymerizationbutalsofromthatoftraditionallivingpolymerization.活性自由基聚合的機(jī)理不僅完全不同于普通自由基聚合機(jī)理，也不同于傳統(tǒng)的活性聚合機(jī)理。Itreliesontheintroductionofareagentthatundergoesreversibleterminationwiththepropagatingradicalstherebyconvertingthemtoafollowingdormantform：活性自由基聚合依賴于向體系中引入一種可以和增長自由基進(jìn)行可逆終止的試劑，形成休眠種：Thespecificityinthereversibleinitiation-terminationstepisofcriticalimportanceinachievinglivingcharacteristics.-。Thisenablestheactivespeciesconcentrationtobecontrolledandthusallowssuchaconditiontobechosenthatallchainsareabletogrowatasimilarrate(ifnotsimultaneously)throughoutthepolymrization.可逆引發(fā)終止使活性中心的濃度能夠得以控制。這樣就可以來選擇適宜的反應(yīng)條件，使得在整個(gè)聚合反應(yīng)過程中(只要沒有平行反應(yīng))所有的分子鏈都能夠以相同的速度增長。Thishas,inturn,enabledthesynthesisofpolymerswithcontrolledcomposition,architectureandmolecularweightdistribution.這樣就可以合成具有可控組成，結(jié)構(gòu)和分子量分布的聚合物。Theyalsoprovideroutestonarrowdispersityend-functionalpolymers,tohighpurityblockcopolymers,andtostarsandothermorecomplexarchitecture.這些還可以提供獲得狹窄分布末端功能化聚合物，高純嵌段共聚物，星型及更復(fù)雜結(jié)構(gòu)高分子的合成方法。ThefirststeptowardslivingradicalpolymerizationwastakenbyOstuandhiscolleaguesin1982.活性自由基聚合是Ostu和他的同事于1982年率先開展的。In1985,thiswastakenonestepfurtherwiththedevelopmentbySolomonetal.ofnitroxide-mediatedpolymerization(NMP).1985年，Solomon發(fā)展。Thisworkwasfirstreportedinthepatentliteratureandinconferencepapersbutwasnotwidelyrecognizeduntil1993whenGeorgesetal.appliedthemethodinthesynthesisofnarrowpolydispersitypolystyrene.但是直到1993年Georges等把這種，。ThescopeofNMPhasbeengreatlyexpendedandnew,moreversatile,methodshaveappeared.NMP的領(lǐng)域已經(jīng)得到很大的延展，出現(xiàn)了新的更多樣化的方法。Themostnotablemethodsareatomtransferradicalpolymerization(ATRP)andpolymerizationwithreversibleadditionfragmentation(RAFT).最引人注目的方法是原子轉(zhuǎn)移自由基聚合和可逆加成斷裂聚合。Upto2000,thisareaalreadyaccountedforonethirdofallpapersinthefieldofradicalpolymerization,asshowninFig.5.1.到2000年，這個(gè)領(lǐng)域的論文已經(jīng)占所有自由基聚合領(lǐng)域論文的三分之一。如圖5.1所示。Naturally,therapidgrowthofthenumberofthepapersinthefieldsince1995oughttobealmosttotallyattributabletodevelopmentinthisarea.很自然自從1995，。Unit6MolecularWeightanditsDistributionsofPolymersThemolecularweightofapolymerisofprimeimportanceinitssynthesisandapplication.對聚合物的合成和應(yīng)用而言，聚合物的分子量是最重要的。Theinterestingandusefulmechanicalpropertieswhichareuniquelyassociatedwithpolymericmaterialsareaconsequenceoftheirhighmolecularweight.令人感興趣的和具有使用價(jià)值的力學(xué)性能與高分子材料存在的唯一的相關(guān)性，而這些性能是聚合物的高分子量帶來的。聚合物材料的高分子量帶來了令人感興趣的和具有利用價(jià)值的力學(xué)性能。Mostimportantmechanicalpropertiesdependonandvaryconsiderablywithmolecularweight.最重要的力學(xué)性能取決于分子量，而且隨著分子量變化而發(fā)生很大的變化。Thus, strengthofpolymerdoesnotbegintodevelopuntilaminimummolecularweightofabout10000isachieved.因此,5000～10000,聚合物的強(qiáng)度才開始顯示出來.Abovethatsize,thereisarapidincreaseinthemechanicalperformanceofpolymersastheirmolecularweightincreases;theeffectlevelsoffatstillhighermolecularweights. Level達(dá)到平衡趨緩分子量大于這個(gè)值的時(shí)候，隨著分子量的增加，聚合物的機(jī)械性能快速增加;達(dá)到更高的分子量的時(shí)候，這種效應(yīng)才變平緩。Inmostinstances,thereissomemolecularweightrangeinwhichagivenpolymerpropertywillbeoptimumforaparticularapplication.在大多數(shù)情況下，對于某種特定的應(yīng)用來說，某種聚合物存在著某一個(gè)分子量范圍。Thecontrolofmolecularweightisessentialforthepracticalapplicationofapolymerizationprocess.聚合物分子量的控制對聚合過程的實(shí)際應(yīng)用而言是必需的。對實(shí)際的聚合過程而言，必須控制聚合物的分子量。Whenonespeaksofthemolecularweightofapolymer, one meanssomethingquitedifferentfromthatwhichappliestosmall-sizedcompounds.當(dāng)人們談到聚合物分子量的時(shí)候，他所指的是和(適用于)低分子化合物的分子量完全不同的另一回事。Polymersdifferfromthesmall-sized compoundsinthattheyarepolydisperseorheterogeneousinmolecularweight.聚合物與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勻的。Evenifapolymerissynthesizedfreefromcontaminantsandimpurities,itisstillnotapuresubstanceintheusuallyacceptedsense.即使聚合物在沒有污物和雜質(zhì)的情況下被合成，在人們廣泛接受的意義上，它仍然不是純物質(zhì)。Polymers,intheirpurestform,aremixtureofmoleculesofdifferentmolecularweights.最純凈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過程中展現(xiàn)的統(tǒng)計(jì)變化。Whenonediscussesthemolecularweightofapolymer,oneisactuallyinvolvedwithitsaveragemolecularweight.當(dāng)我們討論聚合物的分子量，準(zhǔn)確的含義是平均分子量。Boththeaveragemolecularweightandtheexactdistributionofdifferentmolecularweightswithinapolymerarerequiredinordertofullycharacterizeit.為了充分地表征聚合物，不僅要求平均分子量，而且也要求聚合物內(nèi)不同分子量的確切的分布情況。Thecontrolofmolecularweightandmolecularweightdistribution(MWD)isoftenusedtoobtainandimprovecertaindesiredphysicalpropertiesinapolymerproduct.為了獲得和改善聚合物產(chǎn)品的某些理想的物理性質(zhì)，我們經(jīng)常需要控制分子量和分子量分布。Variousmethodsareavailablefortheexperimentalmeasurementoftheaveragemolecularweightofapolymersample.在聚合物樣品平均分子量的實(shí)驗(yàn)測試中有許多方法可以利用。Theseincludemethodsbasedoncolligativeproperties,lightscattering,viscosity,ultracentrifugation,andsedimentation.這些方法基于依數(shù)性，光散射，粘度法，超速離心分離，沉降法。Thevariousmethodsdonotyieldthesameaveragemolecularweight.不同的方法得到不同的平均分子量。Differentaveragemolecularweightsareobtainedbecausethepropertiesbeingmeasuredarebiaseddifferenttowardthedifferentsizedpolymermoleculesinapolymersample.(對同一聚合物)得到了不同的平均分子量，因?yàn)樗鶞y得的性質(zhì)對試樣中不同尺寸的聚合物分子有不同的偏差。Somemethodsarebiasedtowardthelargersizedpolymermolecules,whileothermethodsarebiasedtowardthesmallersizedmolecules.一些方法對較大尺寸的聚合物分子有偏差（傾向性），而另外一些方法則對較小尺寸的聚合物分子有偏差（傾向性）。The result is that the average molecular weights obtained arecorrespondinglybiasedtowardthelargerorsmallersizedmolecules.所獲得的平均分子量分別對較大的或較小的分子有（偏差）傾向性。Themostimportantaveragemolecularweightswhicharedeterminedarethenumber-averagemolecularweightMn,theweight-averagemolecularweightMwandtheviscosity-averagemolecularweightMv.。被測定的最重要平均分子量有數(shù)均分子量Mn,重均分子量Mw,和粘均分子量Mv.Inadditiontothedifferentaveragemolecularweightsofapolymersample,itisfrequentlydesirableandnecessarytoknowtheexactdistributionofmolecularweights.除聚合物樣品的不同的平均分子量外，經(jīng)常需要知道確切的分子量分布。Avarietyofdifferentfractionationmethodsareusedtodeterminethemolecularweightdistributionofapolymersample.各種各樣的不同的分級(jí)方法被用來確定聚合物樣品的分子量分布。Thesearebasedonfractionationofapolymersampleusingproperties,suchassolubilityandpermeability,whichvarywithmolecularweight.這些方法基于使用諸如溶解性，滲透性等性質(zhì)進(jìn)行聚合物樣品的分級(jí)，這些性質(zhì)隨著分子量變化而變化。UNIT7PolymerSolutionDissolvingapolymerisaslowprocessthatoccursintwostages.UNIT7PolymerSolution溶解高分子需要一個(gè)緩慢的過程，這個(gè)過程分兩步發(fā)生。First,solventmoleculesslowlydiffuseintothepolymertoproduceaswollengel. 溶劑分子緩慢地?cái)U(kuò)散到高分子中產(chǎn)生溶脹凝膠。Thismaybeallthathappensif，forexample，thepolymer-polymerintermolecularforcesarehighbecauseofcrosslinking，crystallinity·orstronghydrogenbonding.例如,如果因交聯(lián)，結(jié)晶和很強(qiáng)的氫鍵而形成很大的分子間力，(聚合物的溶解過程)有可能就只停留在這一階段。Butiftheseforcescanbeovercomebytheintroductionofstrongpolymer-solventinteractions,thesecondstageofsolutioncantakeplace.但是如果這些力被強(qiáng)的高分子-溶劑之間相互作用克服，溶解的第二階段就會(huì)發(fā)生。Herethegelgraduallydisintegratesintoatruesolution.即，凝膠逐漸變成一個(gè)真正的溶液。Onlythisstagecanbemateriallyspeededbyagitation.只有這個(gè)階段可以通過攪拌得到明顯促進(jìn)。Evenso,thesolutionprocesscanbequiteslow(daysorweeks)formaterialsofveryhighmolecularweight.雖然如此，對高分子量的材料而言 ，溶解過程是相當(dāng)緩慢的 （幾天或幾個(gè)期）。Solubilityrelationsinpolymersystemsaremorecomplexthanthoseamonglowmolecular-weightcompounds,becauseofthesizedifferencesbetweenpolymerandsolventmolecules,theviscosityofthesystem,andtheeffectsofthetextureandmolecularweightofthepolymer.因?yàn)楦叻肿雍腿軇┓肿又g尺寸上的區(qū)別，體系的粘度以及聚合物分子量及織態(tài)結(jié)構(gòu)的影響等原因，高分子體系的溶解性關(guān)系比低分子量化合物要復(fù)雜得多。Inturn，thepresenceorabsenceofsolubilityasconditions(suchasthenatureofthesolvent，orthe temperature)arevariedcangivemuchinformationaboutthepolymer.當(dāng)條件(溶劑的性質(zhì)或溫度)變化的時(shí)候，有無溶解性又可提供出許多關(guān)于這種聚合物的信息。Asspecifiedintheliterature，thearrangementsofthepolymerchaindifferingbyreasonofrotationsaboutsinglebandsaretermedconformations.正如在文獻(xiàn)中所定義的那樣，由于圍繞著單鍵的旋轉(zhuǎn)而導(dǎo)致的聚合物鏈不同的空間排布叫做構(gòu)象。Insolution,apolymermoleculeisarandomlycoilingmassmostofwhoseconformationsoccupy[‘okjupai]manytimesthevolumeofits在溶液中，聚合物分子是無規(guī)線團(tuán)狀,而大部分構(gòu)象占鏈段分子自身體積的許多倍。Theaveragedensityofsegmentswithinadissolvedpolymermoleculeisof10-4~10-5g/cm3.溶解聚合物分子里的平均鏈段密度是10-4~10-5g/cm3The size of the molecular coil is very much influenced by polymer-solventinteractionforces.聚合物-溶劑之間的作用力對分子線團(tuán)尺寸有很大的影響。Inathermodynamically“good”solvent,wherecontactsarehighlyfavored,thecoilsarerelativelyextended.在熱力學(xué)上的好溶劑中，聚合物-溶劑作用較強(qiáng)，線團(tuán)是相對伸展的。Ina“poor”solventtheyarerelativelycontracted.而在不良溶劑中，線團(tuán)則是相對收縮的。Itisthepurposetodescribethe