高分子的链结构

高分子的链结构1ChainStructureofPolymerPolymerPhysics高分子物理11.1高分子结构的特点和分类CharacteristicandclassificationofpolymerstructureStructureandPropertyofPolymer高分子结构与性能21.1.1高分子的结构特点CharacteristicsofpolymerstructurePolymeriscomposedofmanystructuralunitslinkedbychemicalbonds.(聚合物由许多结构单元通过化学键连接而构成。)Themolecularweightofpolymerisveryhighandhaspolydispersity.(聚合物的分子量很大并具有多分散性。)Themainchainsofpolymercanrotate,leadingtoflexibilityofpolymerchains.Duetothermalmotion,theshape(conformation)ofpolymerchainschangewithtime.(聚合物主链上的化学键可以旋转，是聚合物链柔性的来源。同时，由于热运动，聚合物链的形状(构象)会随时间发生变化。)3TheVanderwallsforceamongstructuralunitsisveryimportant.(聚合物分子链间的范德华作用力非常重要！)Crosslinkingmaygreatlychangepropertiesofpolymers.(交联可以明显地改变聚合物的性能。)Theaggregatestateofpolymermaybecrystallineoramorphous.Theorderofpolymerincrystallinestateissmallerthanthatofsmallmolecules，buttheorderinamorphousstateishigherthanthatofsmallmolecules.(聚合物的聚集态结构可以是结晶态或无定型态。聚合物结晶态的有序度比小分子晶体要低，但无定形高分子的有序度要比非晶小分子要高。)41.1.2高分子的结构层次链结构高次结构(织态结构)聚集态结构(三次结构)近程结构(一次结构)远程结构(二次结构)chemicalcompositionregioisomerismstereoisomerismbranching&crosslinkingbondingsequenceincopolymersize(molecularweightanddistribution)conformation(flexibilityandrigidity)crystallinestateliquidcrystallineamorphousstateorientationstate高分子结构ConfigurationclassificationofpolymerstructureShortrange

structureLongrangestructureChainstructureAggregatestructuretexturalstructuretexturalstructure5ShortrangestructurestructuralunitsorlocalchainsegmentsareinvolvedLongrangestructureentiresinglepolymerchainsareinvolvedAggregatestructurelotsofpolymerchainsareinvolvedHowaboutdoublehelixstructureofDNA?6Polymerstructuresatdifferentlevelsaredifferentbutcorrelated!!!Polymerstructureisthesumofstructuresatdifferentlevels,whichcontributetoapparentpolymerproperties.stereo-regularitystructureofmonomersequenceofcomonomermolecularweightcrystallizability;etc.conformation;liquidcrystal;etc.phaseseparation;crystallizability;etc.miscibility;meltingtemp.;etc.(低次结构决定高次结构！）7Regulationandimprovementofpolymerpropertiescanbeapproachedbychangeofpolymerstructuresatdifferentlevels.

synthesis：

processing：

blending：shortrangestructureandlongrangestructurelongrangestructureandaggregatestructuretexturalstructure81.2高分子链的近程结构Short-rangestructureofpolymerchain91.2.1结构单元的化学组成

CompositionofstructuralunitStructuralunitMainchainSidechaingrouporsubstituente.g.poly(vinylchloride)-

PVCPolymerizationdegree10碳链高分子Carbonchainpolymer

Thepolymermainchainaretotallycomposedofcarbonatomslinkedbychemicalbonds(mostarepreparedbyadditionpolymerization)Difficulttohydrolyze,goodprocessibility,poorthermalstability,easytoflameandage.11聚丙烯

PP

Polypropylene聚异丁烯 PIB Polyisobutylene聚丙烯酸 Poly(acrylicacid)聚甲基丙烯酸甲酯PMMAPoly(methylmethacrylate)哪个甲基？12聚醋酸乙烯酯PVAcPoly(vinylacetate)聚乙烯基甲基醚 PVMEPoly(vinylmethylether)聚丁二烯PBPolybutadiene聚异戊二烯PIPPolyisoprene13聚氯乙烯 PVC Poly(vinylchloride)聚偏二氯乙烯PVDCPoly(vinylidenechloride)聚四氟乙烯PTFEPolytetrafluoroethylene(Teflon)聚丙烯腈 PANPolyacrylonitrile14杂链高分子

HeterochainpolymerThepolymermainchainsarecomposedofcarbonatomsandotheratoms(forexample:O,N,S,Petal.)linkedbychemicalbonds.Preparedbycondensationorring-openingpolymerization.Themainchainshaspolarity.Advantages：goodthermalstability,highstrengthDisadvantages：easytohydrolyzeanddecomposeinalcoholoracid.Applications:engineeringplastics.15聚甲醛POMPolyformaldehyde

聚己二酰己二胺Poly(hexamethyleneadipamide)(Nylon6-6)聚氧化乙烯PEOPoly(ethyleneoxide)聚己内酰胺Poly(-caprolactam)i.eNylon616聚苯醚PPO

Poly(phenyleneoxide),

orPolyphenyleneether聚对苯二甲酸乙二酯PET

Poly(ethyleneterephthalate)聚碳酸酯 PCPolycarbonate17聚醚醚酮PEEKPolyetheretherketone对苯二甲酰对苯二胺PPTAKevlarPoly(p-phenylene-terephthalamide)聚酰亚胺Polyimide18polyester聚酯polyurethane聚氨酯polysulfone

聚砜19元素有机高分子Elementaryorganicpolymer

Thereisnocarbonatominthepolymermainchains,butthesidechainscontaincarbonatom.Possessingboththermalstabilityofinorganicsandelasticityandplasticityoforganics,butthestrengthislow.20无机高分子InorganicpolymerThepolymerarecomposedofnon-carbonatoms.Onlypartialnon-metalelementsinⅢA,ⅣA,ⅤA,ⅥAcanforminorganicpolymers二硫化硅silicondisulfide聚偏磷酸(盐)polyphosphoricacid(orpolyphosphates)聚二氯一氮化磷poly(dichlorophosphazene)211.2.2分子构造单链SinglechainMoleculararchitecture22梯型聚合物LadderchainCarbonfiberFeaturesofladderpolymers:excellentthermalstability.Whensinglechaininaladderringisbrokenuponheating,themolecularweightofthepolymerisunaffected.2324BranchingEffectsonpolymerproperties:crystallinity,flexibility,hardness,density,meltingtemperature,etc.

shortbranches—regularity,crystallinity,

density,meltingtemperature

longbranches—dissolvingpropertyandrheologyinthemelt25InfluenceofgraftingandcrosslinkingonthepropertiesofpolyethyleneTypePropertiesHDPELDPEXPECrystallinity,%9560~70Density,g/ml0.95~0.970.91~0.940.93~1.40Meltingpoint,C135105Workingtemperature,C12080~100100~135TensileStrength,MPa20~4010~2010~100Elongation,%50~40050~80050~600XPE:交联聚乙烯26Crosslinkingpolymers:un-dissolvable,un-meltablestrength,thermalstabilityThermosetresinandvulcanizedrubberarecrosslinkingpolymermaterials.交联crosslinking27VulcanizationofrubberCureofthermosetplasticsCrosslinkingofsaturatedpolyolefins:

radicalattack(forexample：irradiationcrosslinking)281.2.3键接异构BondorderisomerRegio-selectivityofstructuralunitsinpolymerization

vinylmonomers(CH2=CHR)

head-headtail-tailhead-tailaffectingcrystallizability,mechanicalpropertiesandthermalstability29头尾头头+ZnZnCl286%Head-tailstructureisthemajorityinpolymersofvinylmonomers.Head-to-tailHead-to-head3031Head-headandtail-tailstructuresleadingtomorehydroxylleft,thustheabilityofwaterabsorptionincreasesandstrengthisreduced.32Dienemonomers？33Howtodetermineregio-regularity?NMR,IR,chemicalreaction,Pyro-GC,etc.341.2.4立体异构Stereoisomerism旋光异构OpticalisomerismAfterpolymerization,achiralcarbonatomisproducedforvinylmonomers,thustherearetwoopticalisomers.(Forsinglepolymerchain,theopticalactivityisveryweakduetothesmalldifferencebetweenthetwolongchaingroup.)Howtoprepareapolymerwithopticalactivity?35三种类型Isotactic全同立构Atactic无规立构Syndiotactic间同立构Polymerchainsarecomposedofsingleopticalisomers.uniformandcrystallizable.Polymerchainsarecomposedoftwoalternativeopticalisomers,uniformandcrystallizable.Polymerchainsarerandomlycomposedoftwoopticalisomers.Theformertwoarestereo-regularPP,andthelastoneisstereo-irregularPP.non-uniformand

usuallynon-crystallizable36Stereo-configurationaffectspolymerpropertiesPS：

isotacticPS：crystallizable，Tm=240C

，uneasytodissolve

atacticPS：softtemperature80C

，solubleinbenzenePP：

isotacticPP：Tm=175C

，highstrength,usedasfiberandengineeringplastic

atacticPP：soft,additiveforpavingasphalt37Isstereoregularitythenecessaryconditionforpolymercrystallization?Undermostcasesitis,butsomeexceptions:poly(fluoroethylene)poly(vinylalcohol)poly(trichlorofluoroethylene)similarsizesofFandHstrongHbondClisslightlylargerthanF，ButstrongrepulsionbetweenFatoms.38几何(顺反)异构Geometrical(cis-/trans-)isomerismFor1,4-additionofdienemonomerscis-1,4-butadiene,rubbertrans-1,4-butadiene,crystalline,plastics天然橡胶Naturalrubber杜仲胶Gutta-percha39

Stereo-isomerismandregio-isomerismmayoccursimultaneously!401.2.5共聚物的序列结构Sequencestructureofcopolymerscopolymerizationcanimprovesomespecificpropertiesofpolymers

PMMA:

流动性较差，不适合注射成型(由于较强的分子间作用力)

MMA+Scopolymer:

流动性得到改善，可以注射成型

S+ANcopolymer:

抗冲行为、热稳定性、耐化学品性能得到提高

(可用做耐油制品)41

无规共聚物(randomcopolymer)两种或两种以上结构单元沿聚合物链无规分布

ABAABABBAAABABBAAA

Poly(A-co-B)结构单元之间及分子链间的相互作用被改变。溶液性能、结晶性能节力学性能与相应的均聚物不同。42Forexample:聚乙烯(PE)和聚丙烯(PP)是结晶性塑料，但乙烯丙烯无规共聚物是橡胶。聚四氟乙烯(PTFE)不能进行熔融加工，但四氟乙烯和六氟丙烯共聚物是热塑性塑料，可进行熔融加工。43嵌段共聚(blockcopolymer)

AAAAAAAAABBBBBBBBB

polyA-b-polyBorpoly(A-b-B)

SBS:poly(styrene-b-butadiene-b-styrene)preparedbylivinganionicpolymerizationHardHardSoft44SBS：

热塑性弹性体

高温下:可以流动，能够注射成型

低温下:类似交联的橡胶(两端的PS处于玻璃态，充当

“物理交联点”)。

PSPBQuestion:IsBSBblockcopolymerathermoplasticelastomer?45接枝共聚

(graftcopolymer)polyA-g-polyB

(注意顺序：主链在前，侧链在后)46ABS(acrylonitrile-butadiene-styrene):

同时利用无规共聚和接枝聚合物制备的三元共聚物

StructureP(BS)-g-P(SA)orP(AB)-g-PSorP(SA)-g-P(AB)-CH2-CH=CH-CH2-

Rubber-likeelasticity.HighimpactresistanceGoodformabilityChemicalresistance,hightensilestrengthandhardness47交替共聚物(alternatingcopolymer)

ABABABAB

Anexample:Styrene-maleicanhydridealternatingcopolymer

Poly(A-alt-B)48shortrangestructurestructureofunitcarbonchainpolymerheterochainpolymerelementaryorganic

polymerinorganicpolymermoleculararchitecturesinglechainladderchainbranchingcrosslinkingbondorderisomerismvinylmonomer：H-T;H-H;T-Tdienemonomer：1,2;1,4;3,4stereo-isomerismvinylmonomer：opticalisomerism

(isotactic,syndiotactic,atactic)dienemonomer：geometricisomersequenceofcopolymerrandomcopolymerblockcopolymergraftingcopolymeralternatingcopolymerconfiguration491.3高分子链的远程结构Long-rangestructureofpolymerchain501.3.1分子量MolecularWeightSmallmolecule：definitemolecularweightforaspecificsubstancePolymer：distributionofmolecularweight(polydispersity)Forthedetails,seeChapter4OnlywhenMWreachesacertainvalue(criticalMW),polymermaterialsexhibitusefulmechanicalstrength.polarpolymer:DPcri

40non-polarpolymer:DPcri

80StrengthMolecularWeightPolarNonpolarWhenMWisveryhigh(DP>600~700),strengthreachesalimit,butmeltviscosityistoohightoprocess.Plasticsandrubber:broadMWdistribution(highMWpartscontributetostrength,lowMWpartsimproveprocessability.)Fiber:narrowMWdistribution511.3.2内旋转构象ConformationalStateC－C单键的旋转

构象的改变

高聚合度TEMofbacteria’sDNA结构单元间通过共价键相连⇒结构单元不能独立运动⇒熵匮乏(相对n个自由的结构单元！).柔顺性链段(chainsegment)由多个结构单元组成、能够独立运动的单元大量的构象一方面：另一方面：52DuetopresenceofHandothersubstituents,energybarriermustbeovercomeforrotationofsinglebond.largerdistancesmallerrepulsionlowerenergystability:trans>gauche>cistg-g+cistrans正丁烷或聚乙烯内旋转位能图gauche53ForlinearPEchain,theenergylevelofall-transconformationisthelowestT=0K:planarzig-zag(平面锯齿)conformationT>0K:gaucheconformationsappearduetothermalmotion

54Forawith10,000bonds,Thenumberofarrangements310,000=104,771551.3.3分子链的柔顺性

ChainFlexibility56Staticflexibility(静态柔顺性)

flexibilityofpolymerchainatthermodynamicequilibrium

determinedbythedifferenceinthepotentialenergyof

transandgaucheconformation()<kT largeamountofgaucheconformation,andtheshapeofpolymerchainisrandomcoils(无规线团)kT

transconformationisthemajority(thewholepolymerchainisflexible,butlocalisrigid.) >>kT Thepolymerchainisrigid.57Dynamicflexibility(动态柔顺性)

thetransition

ratebetweendifferentconformationsdeterminedbytheenergybarrierbetweendifferentconformations(E)

p:timefortransitionfromtranstogaucheconformationE<<kTtransitionfromtranstogaucheconformationcanbecompletedin1011s.smallp

:gooddynamicflexibilitylargep

:poordynamicflexibility58TemperatureForceSolventExternalFactorsInternalFactorsStructureofmainchainSubstituentsBranchingandcross-linkingLengthofpolymerchainIntermolecularforceCrystallizationFactorsaffectingflexibilityofpolymerchain59Mainchainstructure

lengthofsinglebond顺丁胶conjugateddoublebondrigidity-CH=CH-CH=CH-CH=CH

聚乙炔聚苯NHNHC=OC=O尼龙H-bondrigidity

isolateddoublebondflexibilitySi－O>C－N>C－O>C－C60Sidegroup

polarityinteractionflexibilityPAN<PVC<PPnumberofpolarsidegroupflexibilitypolarity:

1,1-di-substituents<1-mono-substituents—CHCl—CHCl—

poly(1,2-dichloroethylene)

—CH2

—CHCl—

PVC>sizeofsidegroupflexibilityPS<PP<PEnon-polar1,1-di-substituentdistanceofpolymerchainsflexibilitypoly(iso-butylene)(PIB)>PE—CH2

—CCl2

—

PVDC

—CH2

—CHCl—

PVC<61

Chainlength

lengthofmainchainnumberofconformationflexibilitylengthofsidechaininteractionflexibilityButwhenthesidechainistoolong,ithindersrotationofthemainchainandflexibilitydecreases.CH3—CH2—C———COO(CH2)nCH3n:0<1<2<…<18>19>20>…621.4高分子链的构象统计Conformationalstatisticsofpolymerchain631.4.1自由连接链FreelyJointedChain

Freelyjointedchainisjustusedfortheoreticalcalculation,anditdoesnotcorrespondtoanyrealpolymerchain.Thepolymerchainconsistsinnequalone-dimensionallinksoflengthl(withnooccupiedvolume).Thereisnorestrictionontheanglesbetweenthelinks.Noenergyisrequiredtochangetheangles.

Theprobabilityofeachbondatanydirectionisequalandthecontourorfullyextendedlengthofthechainisnl.64Othertwoterms：randomwalk(无规行走)one-dimensionalfreelyjointedchainrandomflight(无规飞行)three-dimensionalfreelyjointedchain65SimulationoffreelyjointedchainN=104ThetraceislikethatofBrownianparticles.Thevolumefractionoftheunitsisverysmall.Therearelotofholesinsidetherandomcoil.66End-to-enddistance(末端距)67Mean-squareofend-to-enddistance

(均方末端距)TotalntermsijTheconformationoffreelyjointedchainisfarfromthatofextendedchain!extendedchain68Originofrubberelasticity69massofunit:micoordinateofithunit:Radiusofgyration(旋转半径)coordinateofcenterofmassn时alsoapplicabletofreelyrotatingchainandGaussianchainRadiusofgyrationissuitableforpolymerchainswithmultiplechainends.r012i质心rifreelyjointedchain701.4.2自由旋转链FreelyRotatingChainModelwithfixedvalencyangleTheangleisrestrictedtolieonacone,butthebondcanrotatefreelyonthesurfaceofthecone.71Mean-squareofend-to-enddistance

TotalntermsTotal2(n-1)termsTotal2(n-m)terms72=l2{n+2[(cos+cos2

+cos3

+…+cosn-1)

(cos

+cos2

+…+cosn-2) (cos+…+cosn-3) +….. +cos]}73=l2{n+2[cos(1-cosn-1)/(1-cos) +cos(1-cosn-2)/(1-cos) +cos(1-cosn-3)/(1-cos)

+….. +cos(1-cos

)/(1-cos)]}=l2{n+2n[cos/(1-cos)]-2[cos/(1-cos)] x[1+cos+cos2+…..+cosn-1)}74n四面体构型cos=1/3751.4.3受阻内旋转链

HinderedRotationChainForarealpolymerchain,therotationofthebondsontheconesisnotfree.Energybarriermustbeovercomeforrotationofthebonds.Theenergybarrierforrotationisnotaconstant,butitvarieswithrotationangle.Bondangle键角Conformationangle构象角76ForPE，trans:

=0,U(t)=0;gauche(gorg')=±120,U(gorg')=3.34kJ·mol-1,298K771.4.4高斯链

GaussianChainThedistributionofchainendforan“equivalentchain”obeysGaussiandistribution.Gaussianchain(1)ThepolymerchaincomprisesNhypotheticalsegments.(2)Eachsegmenthasalengthoflandisrigid.(3)Segmentsarefreelyjointedandthereisnorestrictiononangles.Equivalentfreelyjointedchain:78*Thesame<r2>:<r2>=Nele2

le=<r2>/L*Thesamecontourlength:L=Nele=nlsin(/2)<r2>canbeexperimentallymeasured.在状态下(体积相同)(长度相同)79ForPEfreelyjointedchainfreelyrotatingchainunderconditionextendedchain<r2>Nl22Nl26.76Nl22/3N2l2Kuhnlengthl(bondlength)2.45l8.28l0.82NlForfreelyrotatingchain:contourlength:Nele=Nlcos[(180-)/2]=Nlsin(/2)<r2>=Nele2=2Nl2le=2Nl2/Nlsin(/2)=2.45l(Note:OnlyforfreelyjointedchainthecontourlengthisNl.Forotherchains,thecontourlengthis

Nlsin(/2).80Equivalentfreelyjointedchain—obeysGaussiandistribution;themotionunitisasegment;correspondstorealpolymerchainFreelyjointedchain—obeysGaussiandistribution;themotionunitisa

singlebond;onlyusedfortheoreticalstudy81

Probabilitydistributionfunctionofend-to-enddistanceforfreelyjointedchaininone-dimensionalspaceW(x)Startfromzeropoint(oneendofthechain)Eachstepl(bondlength),nstepsofrandomwalk(numberofbonds)

Whereisthelaststep(theotherendofthechain)located?

End-to-enddistanceofGaussianchainfromstatisticalmethod82

TheprobabilitydistributionfunctionforotherendW(x)is:83

Oneendisfixedatx=0,y=0,z=0PistheprobabilityoftheotherendlocatedinthespacedxdydzZdxdydzXYProbabilitydistributionfunctioninthreedimension三维空间几率分布函数W(xyz)84Probability85

Theprobabilitydistributionfunctioninthree-dimensionalspaceW(xyz):86

Usuallyonlythedistanceoftheendsiscared,andthedirectionoftheendsisignored.∴radiantdistributionfunctionW(R)MeaningofW(R)：

Whenoneendofthechainisfixedatthezeropoint,W(R)istheprobabilitydensityfortheotherendappearinginthesphericalshellfromradiusRtoR+dR.RdR均方末端距87R88Themostprobableend-to-enddistanceR*Meanend-to-enddistanceMeansquarerootend-to-enddistanceForPE,n=1000,l=1.54ÅÅÅÅThreetypesofend-to-enddistance891.4.5柔顺性的表征

CharacterizationofFlexibility2)空间位阻参数(刚性因子)Undisturbedmeansquareend-to-enddistanceunderconditionflexibility3)undisturbeddimension

A(无扰尺寸)Aflexibility1)

characteristicratio

C(特征比)Cflexibility904)Kuhn链节长度

KuhnSegmentLengthL–高分子链围线尺寸ContourlengthofthechainKuhnsegmentlengthleisusuallylargerthancontourlengthofasinglebondsl0.

le/l0canbeusedtocharacterizeflexibilityofpolymerchain.

le/l0flexibility911.4.6蠕虫状链WormlikeChainProposedbyPorodandKratkytodescriberigidpolymerchains.Nbondsoflengthb;freerotation;bondangle:(180-)Averageofprojectionofpolymerchaininthefirstbondcos<1WhenN,cosN0

持续长度：

Averageofprojectioninthefirstbondofpolymerchainwithinfinitelength.持续长度PersistenceLength~lR~

92⇓When0,cos1

⇓⇓93cos194Meansquareend-to-enddistanceHalfofthebondlengthinfreelyjointedchainFlexiblechainRigidchain

195持续长度（自由旋转链）S为两个结构单元间的轮廓线长度s<<l

高分子链为刚性s>>l

分子链失去记忆效应.~~96Advantageof

lk:

itcanbedirectlyexperimentallymeasured.

Advantageof

:

ithasadirect microscopicmeaning.971.4.7真实链:排斥体积

excludedvolumeInrealpolymerchain,therepeatingunitshaveoccupied