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1Charpter 2-13Chapter 2:Polymer ChemistryPolymer chemistryisamultidisciplinarysciencethatdealswiththechemicalsynthesisandchemicalpropertiesofpolymersormacromolecules.AccordingtoIUPACrecommendations,macromoleculesrefertotheindividualmolecularchainsandarethedomainofchemistry.Polymersdescribethebulkpropertiesofpolymermaterialsandbelongtothefieldofpolymer physicsasasubfieldofphysics.Polymerchemistryisthatbranchofone,whichdealswiththestudyofsynthesisandpropertiesofmacromolecules.Polymersareformedbypolymerizationofmonomers.Apolymerischemicallydescribedbyitsdegreeofpolymerisation,molarmassdistribution,tacticity,copolymerdistribution,thedegreeofbranching,byitsend-groups,crosslinks,crystallinityandthermalpropertiessuchasitsglasstransitiontemperatureandmeltingtemperature.Polymersinsolutionhavespecialcharacteristicswithrespecttosolubility,viscosityandgelation.4第二章第二章:高分子化学高分子化学高分子化学高分子化学是一个多学科的科学与它包括聚合物或大分子的化学合成和化学性质。根据IUPAC的建议,大分子是指单个分子链并且属于化学领域。聚合物描述聚合物材料的整体性质和属于高分子物理高分子物理的领域,作为物理学的一个分支。高分子化学是其中一个分支,它涉及合成和大分子性质的研究。聚合物是由单体聚合作用形成的。一种聚合物在化学上是通过它的聚合度,分子量分布,立构规整度,共聚物的分布,支化度,其端基,交联,结晶性和热性能如玻璃化转变温度和熔化温度来描述的。溶液中的聚合物具有相对于溶解度,粘度和凝胶化的特殊性。52.1.Condensation(orStepwise)Polymerization2.1.1 Comparison Between Polymer TypeThetermsadditionandcondensationpolymerswerefirstproposedbyCarothersandarebasedonwhethertherepeatunitofthepolymercontainsthesameatomsasthemonomer.Anadditionpolymerhasthesameatomsasthemonomerinitsrepeatunit.Addition Polymerization62.1缩合(或逐步)聚合2.1.1聚合物类型之间的比较聚合物类型之间的比较加成和缩合聚合物一词由Carothers首次提出,并基于该聚合物的重复单元中是否包含相同原子单体。加成聚合物的重复单元中具有相同单体原子。加成聚合7Theatomsinthepolymerbackboneareusuallycarbonatoms.Condensationpolymerscontainfeweratomswithinthepolymerrepeatunitthanthereactantsbecauseoftheformationofbyproductsduringthepolymerizationprocess,andthepolymerbackboneusuallycontainsatomsofmorethanoneelement.whereA-XcanbewhereB-YcanbeCondensation Polymerization8在聚合物主链上的原子通常是碳原子。在聚合物重复单元中缩合聚合物比反应物有更少的原子,这是由于在聚合过程中副产物的形成,并且聚合物主链通常包含不止一个元素的原子。其中A-X可以是其中B-Y可以是缩合聚合9Polyesterificationinabulkpolymerizationprocesswillbeutilizedtoillustratestepwisegrowth.Polymerformationbeginswithonedialcohol(diol)moleculereactingwithonediacidmolecule,formingwhatwewillcallonerepeatunitoftheeventualpolyester.Thisesterunitcannowreactwitheitheranalcoholoracidgroupproducingchainsendingwitheithertwoactivealcoholfunctionalgroupsortwoactiveacidgroups.10聚酯在本体聚合过程中用于说明逐步增长。聚合物的形成始于一个二元醇(二醇)分子与一种二元酸分子的反应,形成我们所谓的最终聚酯中的一个重复单元。该酯单元现在可与任何一个醇或羧酸基团反应,于任何两种活性的醇官能团或两个活性羧酸基团发生链终止反应。11Thechainwiththetwoalcoholendgroupscannowcondensewithamoleculecontaininganacidendgroup,whilethemoleculewithtwoacidendgroupscanreactwithamoleculecontaininganalcoholfunctionalgroup.Thisreactioncontinuesthroughthemonomermatrixwherevermoleculesofthecorrectfunctionalityhavingthenecessaryenergyofactivationandcorrectgeometrycollide.Theneteffectisthatdimer,trimer,tetramer,etc.,moleculesareformedasthereactionprogresses.12有两个醇端基的链现在可以与含有一个羧酸端基的分子凝结,而具有两个羧酸端基的分子可以与含有一个醇官能团的分子反应。这种反应能通过单体矩阵而继续进行,无论合适官能团的分子具有必要的活化能和正确的几何碰撞。净效果是二聚体,三聚体,四聚体等,分子随着反应的进行而形成。13Chaingrowthreactionsrequireinitiationtobeginchaingrowth.Here,theinitiationofastyrenemoleculeinabulkreactionsystemoccursbymeansofafreeradicalinitiatorR.Thisfreeradicalquicklyaddstoastyrenemonomer,shiftingtheunpairedfreeelectronawayfromtheaddingfreeradical.Thisnewactivechain,whichcontainsanunpairedelectron,addstoanotherstyrenemonomer,withtheunpairedelectronshiftingtowardthechainend.Thiscontinuesagainandagain,eventuallyformingalongpolystyrenechain.14链增长反应需要引发来开始链增长。这里,在一个本体反应体系中的苯乙烯分子的引发的发生是借助于自由基引发剂R。这种自由基迅速添加到苯乙烯单体中,加入自由基将未成对自由电子转移。这个新的活性链,其中包含一个未成对电子,添加到另一个苯乙烯单体,随着未成对电子向链末端转移。这一次又一次的继续,最终形成了一个长的聚苯乙烯链。15ComparisonofStepwiseandChainwisePolymerizationsChainStepGrowthoccursbyadditionofoneunitatatimeAnytwomolecularunitscanreactMonomerconcentrationsdecreasesteadilythroughoutthepolymerizationMonomerdisappearsearlyinthereactionPolymerchainsareformedfromthebeginningofthepolymerizationandthroughouttheprocessPolymerchainlengthincreasessteadilyduringthepolymerizationAveragechainlengthforreactedspeciesremainsapproximatelyconstantthroughoutthepolymerizationAveragemolecularweightforthereaction(forthereactedspecies)increasesthroughoutthepolymerizationAsreactiontimeisincreased,polymeryieldincreasesbutmolecularweightremainsaboutthesameHigh“extents”ofreactionarerequiredtoobtainhighchainlengthsReactionmixturecontainsalmostonlyunreactedmonomer,polymer,andverylittlegrowingpolymerchainReactionsystemcontainsvariousstages,chainlengths,ofproductpresentinacalculabledistribution16逐步和链增长聚合反应的比较链增长逐步增长增长发生一次增加一个单位任何两个分子单元可以反应单体浓度在整个聚合中稳步下降反应早期单体就消失聚合物链的形成从聚合开始并贯穿整个过程聚合过程中聚合物链长稳步增加整个聚合中对反应物的平均链长近似保持恒定在整个聚合中反应(反应物)的平均分子量增加随着反应时间的增加,聚合物的产率增加,但分子量保持大约相同反应高“范围”需要获得高的链长反应混合物含有几乎只有未反应的单体,聚合物,并且有很少的生长聚合物链反应系统包含各个阶段产物,链长,目前在一个可计算分布的产品,172.1.2 Stepwise KineticsForuncatalyzedreactionswherethediacidanddiolarepresentinequimolaramounts,onediacidisexperimentallyfoundtoactasacatalyst.Theexperimentalrateexpressiondependenciesaredescribedintheusualmannerasfollows:whereArepresentsthediacidconcentrationandDthediolconcentration.WhereA=D,wecanwriteRearrangementgivesIntegrationoftheaboveoverthelimitsofA=A0toA=Atandt=0tot=tgives(2.1)(2.2)(2.3)(2.4)182.1.2逐步反应动力学逐步反应动力学对于非催化反应,其中二元酸和二元醇等摩尔量,实验上发现一个二元酸起到催化剂的作用。实验速率表达依赖关系通常用如下的方式描述:其中,A表示二元酸的浓度和D是二醇的浓度。当A=D。我们可以这样写重排整合上述的极限,A=A0到A=At,t=0到t=t(2.1)(2.2)(2.3)(2.4)19Aplotof1/(1-p)2asafunctionoftimeshouldthenbelinearwiththeslope2A02kfromwhichkisdeterminable.Determinationofkatdifferenttemperaturesenablesthecalculationofactivationenergy.Thenumber-averagedegreeofpolymerizationDPNcanbeexpressedasItisconvenienttoexpressEq.(2.4)intermsofextentofreactionp,wherepisdefinedasthefractionoffunctionalgroupsthathavereactedattimet.Thus1-pisthefractionofgroupsunreacted.AtisinturnA0(1-p),i.e.,SubstitutionoftheexpressionforAtfromEq.(2.5)intoEq.(2.4)andre-arrangementgives(2.5)(2.6)(2.7)201/(1-p)2作为时间函数然后应该是线性关系,斜率为2A02k,其中k是确定的。在不同温度下测定的k决定活化能的计算。数均聚合度DPN可以表示为式(2.4)很方便的表达关系,其中反应程度p,其中p定义为在反应时间t时已经反应的官能团的分数。从而1-p为未反应的基团的比例。At等于A0(1-p),即把式(2.5)的At代入式(2.4)并整合得(2.5)(2.6)(2.7)21TherelationshipgiveninEq.(2.8)iscalledtheCarothersequationbecauseitwasfirstfoundbyCarotherswhileworkingwiththesynthesisofnylons(polyamides).Foranessentiallyquantitativesynthesisofpolyamideswherepis0.9999,theDPwasfoundtobeapproximatelyequalto10,000,thevaluecalculatedusingEq.(2.8).Thus(2.8)22在式(2.8)中给出的关系被称为Carothers方程,因为它是由Carothers在尼龙(聚酰胺)的合成工作时第一次发现的。本质上定量合成的聚酰胺的p是0.9999,DP大约等于10,000,这是用式(2.8)得到的值从而(2.8)23TheDPof10,000calculatedabovefornylon-610ismorethanadequateforastrongfiber.Actually,itwouldbedifficulttoforcesuchahighmolecularweightpolymerthroughthesmallholesinthespinneretinthemeltextrusionprocessusedforfiberproduction.Themanypossiblenylonsarecodedtoshowthenumberofcarbonatomsintheamineandacidrepeatunits,respectively.Themostwidelyusednylonfiberisnylon-66.ThehighvalueofpwouldbedecreasedandthevalueofDPalsodecreasedaccordinglyifacompetingcyclizationreactionoccurred.24DP计算达10000以上的尼龙-610对于一个强力纤维是足够的。实际上,很难得到如此高分子量的聚合物,通过喷丝头的小孔熔融挤出,对于纤维生产的过程中。许多可能的尼龙被编码,分别表示胺和羧酸重复单元中的碳原子数目。最广泛使用的尼龙纤维是尼龙-66。高的p值减少和DP值也相应地减少,如果发生一个竞争环化反应。25Sincethevaluesofkatanytemperaturemaybedeterminedfromtheslope(2kA0)ofthelinewhen1/(1-p)2isplottedagainstt,onemaydetermineDPNatanytimetfromtheexpression.Returningagaintoconsiderthesynthesisofpolyesters,generallymuchlongerreactiontimesarerequiredtoeffectformationofhighpolymerinuncatalyzedesterificationsthanforacid-orbase-catalyzedsystems.Forcatalyzedsystemssincetheaddedacidorbaseisacatalyst,itsapparentconcentrationdoesnotchangewithtime;thusitneednotbeincludedinthekineticrateexpression.Insuchcasesthereactionfollowstherateexpression.(2.9)(2.10)ForA=Bwehave(2.11)26由于在任何温度下的k值都可从直线斜率(2kA0)中确定,当1/(1-p)2对t作图,一个任何时间t下可确定的DPN从表达式中得到回过头再考虑的聚酯的合成中,在非催化酯化反应比是酸或碱催化体系,通常需要更长的反应时间影响高聚物的形成。对于催化体系,因为所添加的酸或碱为催化剂时,其表观浓度不随时间而变化,因此它不需要在动力学速率表达式中被包括。在这种情况下,反应遵循速率表达式。(2.9)(2.10)当A=B时我们有(2.11)27whichgivesonintegrationandsubsequentsubstitutionRearrangementgiveswhichpredictsalinearrelationshipof1/(1-p)withreactiontime,asshownintherightfigure.Fig.Plotofchainlengthasafunctionofreactiontimefortheacid-catalyzedcondensationofethyleneglycolwithterephthalicacid.(2.12)(2.13)28通过和合并和随后的替代给出重排得它预测了1/(1-p)的随反应时间的线性关系,在右图中显示。图图.链长是根据乙二醇与对苯二甲酸的酸催化缩合反应的反应时间确定(2.12)(2.13)29Forsuchsecond-orderreactions,DP=A0kt+1.TheeffectoftimeonDPcanbedemonstratedusingA0=2mol/Landk=10-2L/molsatthereactiontimesof1800,3600,5400s.Thus,DPincreasesfrom37to73to109.Usefulhighmolecularweightlinearpolymersarenotobtainedunlessthevalueforthefractionalconversionpisatleast0.990,i.e.,aDPgreaterthan100.Itisimportanttonotethattherateconstantkforreactionsofmonofunctionalcompoundsisessentiallythesameasthatfordifunctionalcompounds,andhencethesekvalues,whichareessentiallyunchangedduringthereaction,canbeusedforpolycondensationreactions.Likewise,asisthecasewithreactionsofsmallmolecules,therateconstantkincreaseswithtemperatureinaccordancewiththeArrheniusequationshownbelow.Theenergiesofactivation(Ea)arealsocomparabletothoseformonofunctionalreactants.(2.14)(2.15)30对于这样的二级反应,DP=A0kt+1。DP的时间效应可以用A0=2mol/L和k=10-2L/mols在1800,3600,5400s时的反应时间来演示。因此,DP从37增加到73再到109。有用的高分子量线型聚合物不能获得,除了分数的转换p值至少是0.990,即,DP大于100。重要的是要注意是对于单官能化合物反应的速率常数k在基本上与双官能化合物的是相同的,因此这些k值在反应过程中基本是不变的,也可用于缩聚反应。同样地,小分子的反应的情况下,速率常数k随温度增加,与如下所示的Arrhenius方程一致。活化能(Ea)也比得上那些单官能反应物。(2.14)(2.15)312.1.3 Polycondensation MechanismsProposedmechanismsforpolycondensationsareessentiallythesameasthoseproposedintheorganicchemistryofsmallermolecules.Herewewillbrieflyconsiderseveralexamplestoillustratethissimilaritybetweenproposedmechanismsforreactionsinvolvingsmallermoleculesandthosethateventuallyproducepolymers.Forinstance,thesynthesisofpolyamides(nylons)canoftenbeenvisionedasasimpleSN2typeofLewisacidbasereactionwiththeLewisbasenucleophilicamineattackingtheelectron-poor,electrophiliccarbonylsitefollowedbylossofaproton.Asimilarmechanismcanbeproposedformostpolyesterifications.322.1.3 缩聚反应机理缩聚反应机理提出的缩聚反应机理基本上与那些在有机化学中提出更小分子(的机理)是相同的。在这里,我们将简单地考虑几个例子来说明涉及小分子反应的机理和最终产生的聚合物反应的机理之间的相似性。例如,聚酰胺(尼龙)的合成通常可以设想为Lewis酸碱反应的SN2类型,Lewis碱亲核性的胺进攻缺电子的亲电的羰基位点,随后损失一个质子。对于大所数的聚酯的类似的机理被提出。33andarelatedpathwayBelowareanumberofresonanceformsfortheisocyanatemoietyillustratingtheoverallelectrophilicnatureofthecarbonatom,givingoverall34相关途径下面是一些异氰酸酯基的共振式,图解总体碳原子的亲电子性质,给出全部35anelectronarrangementwhichcanbedescribedbyPolyurethaneformationoccurswithattackofthenucleophilicalcoholattheelectron-poorisocyanatecarbonwithaprotonshiftfollowedbyarearrangementtotheurethanelinkage.36电子排列可通过以下描述聚氨酯的形成是通过亲核性的醇攻击与质子移位后跟一个重排的氨基甲酸酯键的缺电子的异氰酸酯基碳而发生。37Polyetherformations,suchastheformationofpoly(ethyleneoxide)fromethyleneoxide,canoccureitherthroughacidorbasecatalysisasdepictedbelow.whereX=-OH,-OR.Again,themechanisticpathwayssuggestedforcondensationsinvolvingsmallermoleculescangenerallybedirectlyappliedtopolycondensationprocesses.38聚醚成因,如由环氧乙烷形成聚环氧乙烷,通过如下所述的酸或碱催化而发生。其中X=-OH,-OR再次,机理途径建议对涉及小分子缩合通常可以直接应用到缩聚反应的进程。392.1.4 Synthetic RoutesTheprevioussectionscontainthegeneralsynthesisforanumberofimportantcondensationpolymers.Herewewillconsiderbrieflythethreemainsynthetictechniquesutilizedinthesynthesisofcondensationpolymers.Thiswillbefollowedbyadiscussionofsomeconsiderationsthatmustbetakenintoaccountwhenchoosingagivensyntheticprocedureutilizingspecificexamplestoillustratethepoints.Themelttechniqueisalsoreferredtobyothernamestodescribethesameorsimilarprocesses.Thesenamesincludehighmelt,bulkmelt,andsimplybulkorneat.Themeltprocessisanequilibrium-controlledprocessinwhichpolymerisformedbydrivingthereactiontowardcompletion,usuallybyremovalofthebyproduct.ForpolyesterificationsinvolvingtheformationofwaterorHCl,thedrivingforceistheelimination,generallybyacombinationofreducedpressureandappliedheat,ofthewaterorHCl.402.1.4合成路线合成路线前一节中包含的一般合成的一些重要的缩合聚合物。在这里,我们将简单地考虑在缩合聚合物的合成中使用的三个主要的合成技术。讨论一些必须的考虑因素是紧随其后的,必须在选用特定的例子来说明各点给定的合成方法。熔融技术也被指通过别名来描述相同或相似的过程。这些名称包括高熔融,本体熔融和简单本体或整齐。熔融过程一个平衡控制的过程在其中由朝向反应结束驱动,通常通过去除产品形成聚合物。有水或HCl生成的聚酯,驱动力是消除,一般要综合减压和加热,水或HCl的。41Reactantsareintroducedalongwithanyaddedcatalysttothereactionvessel.Heatisappliedtomeltthereactants,permittingtheirnecessaryintimatecontact.Heatingcanbemaintainedatthereactionmelttemperatureorincreasedaboveit.Pressureisreduced.Typicalmeltpolycondensationstakeseveralhourstoseveraldaysbeforethedesiredpolymericproductisachieved.Yieldsarenecessarilyhigh.Solutioncondensationsarealsoequilibriumprocesses,withthereactionoftendrivenbyremovalofthebyproductbydistillationorbysaltformationwithaddedbase.Reactantsgenerallymustbemorereactiveincomparisonwiththemelttechnique,sincelowertemperaturesareemployed,withanumberofsolutionprocessesoccurringnearroomtemperature.Solvententrapmentisaproblem,butsinceareactionmayoccurunderconsiderablyreducedtemperaturescomparedtothemelttechnique,thermallyinducedsidereactionsareminimized.Sidereactionswiththesolventhavebeenaprobleminsomecases.Becausethereactantsmustbequiteenergetic,manycondensationsarenotsuitableforthesolutiontechnique.42反应物以及任何加入到反应容器的催化剂被引入。加热以熔化反应物,从而允许他们能有必须的紧密接触。加热应保持在该反应的熔融温度或往上增加(熔融温度以上)。压力降低。典型的熔融缩聚需要数小时到数天在制得所需的聚合产物之前。产量必然是高。溶液缩合也是平衡过程,反应通常由蒸馏除去副产物或加入碱形成盐产生驱动。与熔融技术相比反应物通常必须是更具反应性,由于较低的温度被采用,与在接近室温下一些溶液过程的发生。溶剂滞留是个问题,但与熔融技术相比在温度显着降低下反应仍会发生,热引起的副反应是最小化的。溶剂副反应某些情况下一直是一个问题。因为反应物必须有相当有活力,因此许多缩合对溶液技术是不适合的。43Theinterfacialtechnique,whileold,onlygainedpopularitywiththeworkofMorganandCarraherinthe1960sand1970s.Manyofthereactionscanbecarriedoutunderessentiallynonequilibriumconditions.Thetechniqueisheterophasic,withtwofast-reactingreactantsdissolvedinapairofimmiscibleliquids,oneofwhichisusuallywater.TheaqueousphasetypicallycontainstheLewisbaseadiol,diamine,ordithiolalongwithanyaddedbaseorotheradditive.TheorganicphaseconsistsofaLewisacid,suchasanacidchloride,dissolvedinasuitableorganicsolvent,suchastoluene,octane,orpentane.Reactionoccursneartheinterface(hencethename).Thetechniqueofferstheabilitytosynthesizeawidevarietyofpolymersrangingfrommodificationofcotton,polyestersynthesis,synthesisofnucleicacids,andsynthesisofpolycarbonates,thelastbeingtheonlypolymerproducedonalargeindustrialscaleusingtheinterfacialtechnique.44界面技术,虽然旧,只得到普及与Morgan和Carraher在20世纪60年代和70年代的工作。许多的反应基本上可以非平衡条件下进行。该技术是多相,用溶解在对不互溶的液体,其中一种通常是水2快速反应的反应物。水相通常含有路易斯碱-二醇,二胺,或与任何添加的碱或其它添加剂二硫醇-沿。有机相由一种路易斯酸,如酰氯,将其溶于适当的有机溶剂,如甲苯,辛烷,或戊烷。发生反应的界面(因此而得名)附近。该技术提供了以合成各种聚合物从改性棉,聚酯合成,合成的核酸,合成聚碳酸酯,最后被制作在大的工业规模使用的界面技术仅有的聚合物的能力。45Therightfiguredescribesasimpleassemblythatcanbeputtogetherrapidlytoformnylonwiththeinterfacialtechnique.Afewdropsofphenolphthaleinaddedtotheaqueousphasewillgiveamorecolorfulnylonmaterial.Whileaqueousorganicsolventsystemsaretherule,thereareanumberofotherinterfacialliquidgasandnonaqueousliquidsystems.Withallthepotentialthattheinterfacialsystemoffers,ithasnotattractedwideindustrialusebecauseofthehighcostofthenecessarilyreactivemonomersandtheaddedexpenseoftryingtocopewithsolventremovalandrecovery.(Anoteofcaution:diamine,carbontetrachloride,andacidchlorideareharmful,andthereactionshouldbecarriedoutwithadequateventilationandothernecessarysafetyprocedures,includingrubbergloves.)Fig.Self-propelledinterfacialspinningofnylon-610inthe“nylonropetrick.”46右图描述了一个简单的程序集,可以放在一起迅速形成尼龙与界面技术。酚酞数滴加入到水相中将给出一个更加丰富多彩的尼龙材料。而含水有机溶剂体系是规则,还有一些其他的界面液体-气体和非水液体的系统。与所有的界面系统提供了可能,但还没有引起由于一定的反应性单体的高成本和设法应付溶剂去除和回收的额外费用的广泛的工业用途。(一值得注意的问题:二胺,四氯化碳,和酰氯是有害的,反应应进行充分通风等必要的安全程序,包括橡胶手套。)图图.Self-propelledinterfacialspinningofnylon-610inthe“nylonropetrick.”47Inprinciple,anydibasicacidwillcondensewithanydiolordiamine.Inpractice,fewsuchcondensationshavebeenutilizedonanindustrialscaleforavarietyofreasons,includingavailabilityofinexpensivecomonomersinlargequantityandundesirablechemicalandphysicalpropertiesofthesynthesizedpolymer.Forinstance,severalcompanieswereinterestedinthesynthesisofaromaticaminesforcommercialuse.Aromaticaminesofferedmuchgreatertearresistanceandstrengthcomparedwithanaliphaticnylonsuchasnylon-66.Whilearomaticaminescouldbesynthesizedusingseveralroutes,eachproducedasolidnylonwhichwasonlywithdifficultysolubleinalimitednumberofundesirablesolvents.Solutionofthenylonwasnecessaryforfabricationofthepolymer.Morganandothersnotedthatsomepolymersformedwithrapidstirringwouldremaininsolutionfordifferentperiodsoftime.Todayaromaticamides,underthenamearamids,aresynthesizedusingrapidlystirredsystemswhichpermitthearomaticnylontoremaininsolutionlongenoughtopermitfabrication.48原则上,任何二元酸会凝结与任何二元醇或二胺。在实践中,一些这样的冷凝已被用于在工业规模上对各种原因,包括廉价的共聚单体的数量大,所合成的聚合物的不期望的化学和物理特性的可用性。举例来说,有几家公司分别拥有芳香胺用于商业用途的合成。芳香胺提供更大的抗撕裂性和强度与脂肪族尼龙,如尼龙66相比。而芳族胺可以用多种途径来合成,各制作了仅与困难易溶于不良的溶剂数目有限的固体尼龙。尼龙的溶液是必需的聚合物的制造。摩根等人指出,在快速搅拌下形成的一些聚合物将留在溶液中的不同时期。今天芳香酰胺,以商品名芳族聚酰胺,使用快速搅拌系统,其允许该芳香族尼龙保持在溶液中足够长的时间,以允许制造合成。49Theuseofexcessdiol,whileproducingthepolyesteratanacceptablerate,effectivelydecreasesmolecularweight.Thisisovercomebysubsequentremovaloftheexcessethyleneglycol.Thenecessityofusingtwostepsintheproductionofhighmolecularweightpolyesterisundesirableintermsofbothtimeandmaterial.Poly(ethyleneterephthalate)isthebestknownpolyesterbeingusedasafilm(Mylar)andasafiber(DacronandTerylene).Itcanbeproducedusinganyofthethreemajorpolycondensationprocedures.Itcanbepreparedrapidlyfromtheacidchlorideusingtheaqueousinterfacialsystem,givingpoortogoodyieldandshorttolongchainlengths.Duetotheexcessivecostofacidchlorides,theinterfacialtechniqueofsynthesisispresentlyruledoutindustrially.Insolutionandbulk,thepolymerizationrateisslow,soexcessethyleneglycolisemployedtoincreasetheesterificationrate.50使用过量的二元醇,同时产生的聚酯在可接受的速率,从而有效地降低分子量。这是通过随后除去过量的乙二醇克服。用在生产高分子量聚酯的两个步骤的必要性,是不希望的在时间和材料方面。聚(对苯二甲酸乙二醇酯)是最有名的聚酯被用作薄膜(聚酯薄膜)和作为纤维(涤纶和涤纶)。它可以使用任何的三大缩聚的方法来制备。它可以迅速地从酰氯使用水性界面系统做好准备,以良好的产率和短到长链的长度给穷人。由于酸氯化物的过度成本,合成的界面技术目前排除了工业上。在溶液和本体,聚合速率是缓慢的,所以过量的乙二醇被用来提高酯化率。51Terephthalicacidisinsolubleinmostcommonorganicsolventsandisalsohighmelting(300C),compoundingtheproblemofutilizingitdirectlyforbulkandsolutionsyntheses.Thus,thetransesterificationreactionutilizingthedimethylesterofterephthalicacidwithremovalofmethanolandsubsequentremovalofthe“excess”glycoloffersanattractivealternative.Yetbecausethenecessarytechnology,includingfacilities,isalreadypresenttohandleterephthalicaciditself,thisalternativewillprobablynotbecomeamajorpartintheindustrialsynthesisofpoly(ethyleneterephthalate).Thus,considerationofpreviousinvestmentoftimeandfacilitiesisimportantindecidingontheparticularpolycondensationtechniquetobeutilized.52对苯二甲酸是不溶于大多数普通的有机溶剂,也是高熔点(300C),复合直接使用它为本体和溶液的合成的问题。因此,利用对苯二甲酸二甲酯与除去甲醇和“过剩”乙二醇的后续祛瘀的酯交换反应提供了一个有吸引力的替代方案。然而,由于必要的技术,包括设施,已经存在以处理对苯二甲酸本身,这种替代可能不会成为在工业合成聚(对苯二甲酸乙二醇酯)的一个主要部分。因此,考虑以前的时间和便利的投资是在决定要使用的特定缩聚技术重要。53TableComparisonofRequirementsforDifferentPolycondensationTechniquesThetablecontainsacomparisonofthethreesystems.Otheroften-notedliabilities,strengths,andcomparisonsofthesystemsincludethefollowing.Acharacteristicofmeltpolycondensationsisthattheyareslowandrequirethatconversionbehighbeforehighpolymerisformed.Mostmeltsystemsutilizelessreactivereactantsthancalledforinsolutionandinterfacialsystems.Thus,highertemperaturesarenecessarytoachieveareasonablereactionrate.Undesirablesidereactions,depolymerization,anddegradationofthermallyunstablereactantsandproductscanoccuratsuchelevatedtemperatures.54表表为不同的缩聚技术要求的比较该表包含三个系统的比较。其他经常提到的负债,优势,以及系统的比较包括以下内容。熔融缩聚的一个特点是,他们是缓慢的,并要求转化为高高分子形成之前。大部分融化系统利用较不活泼的反应物在溶液中和界面系统比要求。因此,更高的温度是必要的,以实现合理的反应速率。不希望的副反应,解聚,和热不稳定的反应物和产物的降解可发生在这样的高温下。55Ontheotherhand,thelessreactivereactantsaregenerallylessexpensivethanthosecalledforinsolutionandinterfacialsyntheses.Theneedfornear-equivalenceofreactantstoachievehighpolymersismuchgreaterforthemeltprocessthanfortheothertwoprocesses.Solutionandinterfacialsystemshavetheaddedexpenseofsolventutilizedinthereactionsystemandsubsequentsolventremovalandrecoveryfromthepolymer.Thesolutionandinterfacialsystemsareoftencollectivelyknownasthelow-temperaturemethods.Assetsofthelow-temperaturemethodsoftencitedincludeuseofcis,trans,oropticallyactivestructureswithoutrearrangement;directpolymerizationtopolymercoatings,fibrousparticles,smallarticles,wires,fibers,andfilms;andthepossiblesynthesisofthermallyunstableproductsanduseofthermallyunstablereactants.Mostindustrialprocessesutilizethemeltandsolutiontechniques,althoughtheinterfacialtechniqueisgaininglimiteduse.56另一方面,在较低反应性的反应物通
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