高分子物理浙江大学1高分子的链结构ChainStructureofPolymers2

1、polymer physicspolymer physicspolymer physics高分子物理高分子物理高分子物理高分子物理高分子物理高分子物理1.1 1.1 高分子结构的高分子结构的特点和分类特点和分类characteristic and classification of polymer structure structure and property of polymer高分子结构与性能1.1.1 1.1.1 高分子的结构特点高分子的结构特点characteristics of polymer structurepolymer is composed of many structu

2、ral units linked by chemical bonds.the molecular weight of polymer is very high and has polydispersity.the main chains of polymer can rotate, leading to flexibility of polymer chains. due to thermal motion, the shape (conformation) of polymer chains change with time.the van der walls force among str

3、uctural units is very important.crosslinking may greatly change properties of polymers.the aggregate state of polymer may be crystalline or amorphous. the order of polymer in crystalline state is smaller than that of small molecules，but the order in amorphous state is higher than that of small molec

4、ules.1.1.2 1.1.2 高分子的结构层次高分子的结构层次链结构链结构高次结构高次结构聚集态结构聚集态结构(三次结构三次结构)近程结构近程结构(一一次结构次结构)远程结构远程结构(二二次结构次结构)chemical compositionregioisomerismstereoisomerismbranching & crosslinkingbonding sequence in copolymersize (molecular weight and distribution)conformation (flexibility and rigidity)crystalline

5、stateliquid crystallineamorphous stateorientation state高分子结构高分子结构configurationclassification of polymer structureshort range structurelong range structurechain structureaggregate structuretextural structuretextural structureshort range structurestructural unit or local chain segment is involvedlong

6、range structureentire single polymer chain is involvedaggregate structuredifferent polymer chains are involvedhow about double helix structure of dna?polymer structures at different levels are different but correlated!polymer structure is the sum of structures at different levels, which contribute t

7、o apparent polymer properties.stereo-regularitystructure of monomersequence of comonomermolecular weightcrystallizability, etc.conformation; liquid crystal; etc.phase separation; crystallizability; etc.miscibility, etc.regulation and improvement of polymer properties can be approached by change of p

8、olymer structures at different levels. synthesis： processing： blending：short range structure and long range structurelong range structure and aggregate structuretextural structure1.2 1.2 高分子链的近程结构高分子链的近程结构short-range structure of polymer chain1.2.1 1.2.1 结构单元的化学组成结构单元的化学组成 composition of structural

9、unitstructural unitmain chainside chain group or substituente.g. polyvinyl chloride - pvch2cchclnpolymerization degree 碳链高分子碳链高分子carbon chain polymer the polymer main chain are totally composed of carbon atoms linked by chemical bonds (most are prepared by addition polymerization)聚丙烯聚丙烯pp polypropyl

10、enech2chch3n聚异丁烯聚异丁烯pib polyisobutylene聚丙烯酸聚丙烯酸polyacrylic acid聚甲基丙烯酸甲酯聚甲基丙烯酸甲酯pmmapolymethyl methacrylatech2cch3nch3ch2ccnhohoch2ccnch3ooch3聚醋酸乙烯酯聚醋酸乙烯酯pvac polyvinyl acetate聚乙烯基甲基醚聚乙烯基甲基醚 pvmepolyvinyl methyl etherch2ccnhoch3o聚丁二烯聚丁二烯pb polybutadienech2chchch2n聚异戊二烯聚异戊二烯 pip polyisoprenech2cnhch3o

11、ch2cchch2nch3聚氯乙烯聚氯乙烯 pvc polyvinyl chloridech2hccln聚偏二氯乙烯聚偏二氯乙烯 pvdcpolyvinylidene chloride聚四氟乙烯聚四氟乙烯 ptfe polytetrafluoroethylene (teflon)聚丙烯腈聚丙烯腈 pan polyacrylonitrilech2cclnclcf2cf2nchch2ncn 杂链高分子杂链高分子 heterochain polymercarbon atoms and other atoms (for example: prepared by condensation or ring

12、-opening polymerization. the main chains has polarity. advantages：good thermal stability, high strength disadvantages：easy to hydrolyze and decompose in alcohol or acid. applications: engineering plastics.聚甲醛聚甲醛 pom polyformaldehyde och2n聚己二酰己二胺聚己二酰己二胺 polyhexamethylene adipamide (nylon6-6)聚氧化乙烯聚氧化乙

13、烯 peo poly(ethylene oxide)och2n2nhch26nhcoch24con聚己内酰胺聚己内酰胺 poly( -caprolactam)i.e nylon 6coch25nhn聚苯醚 ppopolyphenylene oxide, or polyphenylene etheroch3ch3n聚对苯二甲酸乙二酯 pet polyethylene terephthalatecocooch2ch2on聚碳酸酯 pc polycarbonateococnch3ch3o聚醚醚酮聚醚醚酮 peek polyether ether ketone对苯二甲酰对苯二胺对苯二甲酰对苯二胺 pp

14、ta kevlar poly(p-phenylene-terephthalamide)coooncnonncohh聚酰亚胺聚酰亚胺 polyimidenccoonccooonororccoonch3ch3nocoo聚砜oospolysulfonepolyester聚酯polyurethane 聚氨酯rorccoonhnhon 元素有机高分子元素有机高分子elementary organic polymer there is no carbon atom in the polymer main chains, but the side chains contain carbon atom.nos

15、ich3ch3 无机高分子无机高分子 inorganic polymerthe polymer are composed of non-carbon atoms.only partial non-metal elements in a, a, a, a can form inorganic polymersssissssisssisspopooooopnpnclclclcl二硫化硅 silicon disulfide聚偏磷酸(盐) polyphosphoric acid(or polyphosphates)聚二氯一氮化磷 poly(dichloro phosphazene)1.2.2 1.2.

16、2 分子构造分子构造单链 single chainch2chpolystyrenemolecular architecture梯型聚合物梯型聚合物 ladder chainch2chcnch2chcnch2chcnch2chcnch2chcnch2chcnchccnchccnchccn聚合脱氢环化carbon fiberoonh2nh2h2nh2noooonnnnoon+branchingeffects on polymer properties： crystallinity, flexibility, hardness, density, melting temperature, etc.

17、short branchesregularity, crystallinity, density, melting temperature long branchesdissolving property and rheology in the meltinfluence of grafting and crosslinking on the properties of polyethylene typepropertieshdpeldpexpecrystallinity, %956070density, g/ml0.950.970.910.940.931.40melting point, c

18、135105working temperature, c12080100100135tensile strength, mpa2040102010100elongation, %504005080050600crosslinking polymers：undissolvable, unmeltable strength 、thermal stabilitythermoset resin and vulcanized rubber are crosslinking polymer materials.交联交联 crosslinkingaabbcccaaaabbaaaabbaabbaavulcan

19、ization of rubbercure of thermoset plasticscrosslinking of saturated polyolefins: radical attack (for example：irradiation crosslinking)h2cchch2ch3shcchch2ch3hcchch2ch3ss1.2.3 1.2.3 键接异构键接异构 bond order isomerregio-selectivity of structural units in polymerization vinyl monomers (ch2=chr) head-head ta

20、il-tail head-tailaffecting crystallizability, mechanical properties and thermal stability头尾头头ch2chclch2chclch2chclchch2clh2cchclch2ch*clch2chchch2ch2chchch2+ zn zncl286%head-tail structure is the majority in polymers of vinyl monomers.head-to-tailhead-to-headccoccoooooccccooooohhoohhohead-to-tailh2c

21、cch2ch2ccch2cch3ch3ch3ch3ccoccoooooh2ccch2ch2ccch2cch3ch3ch3ch3ccccooooohohohohhead-to-headohohohohoooo+ chopva维尼纶head-head and tail-tail structures leading to more hydroxyl left,thus the ability of water absorption increases and strength is reduced.n h2c=ch-ch=ch2( ch2-ch=ch-ch2 )n1,4-addition1,2-a

22、ddition( ch2-ch )nch=ch2ch2cchch3ch21234how to determine regio-regularity?nmr, ir, chemical reaction, etc.1.2.4 1.2.4 立体异构立体异构 stereoisomerism旋光异构旋光异构 optical isomerismcchhhryx*cchhrhyx*due to co-existence of meso- and racemic isomers, the whole polymer material exhibits no optical activity. after p

23、olymerization, a chiral carbon atom is produced for vinyl monomers, thus there are two optical isomers.cccrrhhhhcccrrhhhhcccrrhhhhmeso (m) (内 消 旋 )racemic (r) (外 消 旋 ）(for single polymer chain, the optical activity is very weak due to the small difference between the two long chain group.)三种类型isotac

24、tic 全同立构全同立构atactic 无规立构无规立构syndiotactic 间同立构间同立构polymer chains are composed of single optical isomers. uniform and crystallizable.polymer chains are composed of two alternative optical isomers, uniform and crystallizable.polymer chains are randomly composed of two optical isomers.non-uniform and no

25、n-crystallizablethe former two are stereo-regular pp, and the last one is stereo-irregular pp.stereo-configuration affect polymer properties ps： isotactic ps：crystallizable，tm=240 c ，uneasy to dissolve atactic ps：soft temperature 80 c ，soluble in benzene pp： isotactic pp： tm=175 c ，high strength, us

26、ed as fiber and engineering plastic atactic pp： soft, additive for paving asphaltis stereoregularity the necessary condition for polymer crystallization?ccnhhhfunder most cases it is, but some exceptions：ccnhhhohccnfclclclpoly(fluoroethylene) poly(vinyl alcohol) poly(trichloro fluoroethylene)similar

27、 sizes of f and hstrong h bondcl is slightly larger than f，but strong repulsion between f atoms.几何几何(顺反顺反)异构异构 geometrical (cis-/trans-) isomerismfor 1,4-addition of diene monomersch3ch3ch3ch3cis-1,4-butadiene, rubbertranss-1,4-butadiene, crystalline, plastics 天然橡胶 natural rubber杜仲胶 gutta-percha ste

28、reo-isomerism and regio-isomerism may occur simultaneously!1.2.5 1.2.5 共聚物的序列结构共聚物的序列结构sequence structure of copolymerscopolymerization can improve some specific properties of polymers pmma: poor flow behavior and not suitable for injection-molding (strong intermolecular interaction). mma+s copolyme

29、r: improved flow behavior, suitable for injection molding s+an copolymer: impact resistance, thermal stability and chemical resistance are improved (can be used as oil-resistant parts). 无规共聚物无规共聚物 (random copolymer) two or more monomer units distribute along the polymer chain randomly abaababbaaabab

30、baaa the interaction among structural units and the intermolecular interaction are altered. the solution properties, crystallizability and mechanical properties of the copolymer are different from the corresponding homopolymers.for example: pe and pp are plastics, but ep random copolymer is rubber.

31、ptfe(聚四氟乙烯聚四氟乙烯) is a plastics. molten processing is impossible, but copolymer of tetrafluoroethylene and hexafluoropropylene is a thermoplastic.嵌段共聚嵌段共聚 (block copolymer) aaaaaaaaabbbbbbbbb polya-b-polyb or poly(a-b-b) sbs (styrene-b-butadiene-b-styrene): prepared by living anionic polymerizationcc

32、cccccccccccccccchardhardsoft sbs： thermoplastic elastomer high temp: can flow and can be processed by injection molding. low temp: like crosslinking rubber (ps chains at both ends are glassy, “physical” crosslinking). pspb接枝共聚接枝共聚 (graft copolymer)a a a a a a a a a a a a a a a a a a abbbbbbbbbbbbbpo

33、lya-g-polyb abs (acrylonitrile-butadiene-styrene): ternary copolymer prepared by combination of random copolymerization and grafting polymerization. structure p(bs)-g-p(sa) or p(ab)-g-ps or p(sa)-g- p(ab)-ch2-ch=ch-ch2- rubber-like elasticity. high impact resistancegood formabilitychemical resistanc

34、e, high tensile strength and hardness交替共聚物交替共聚物（alternating copolymer） abababab an example:styrene-maleic anhydride alternating copolymer short range structurestructure of unitcarbon chain polymerheterochain polymerelementary organic polymerinorganic polymermolecular architecturesingle chainladder c

35、hainbranchingcrosslinkingbond orderisomerismvinyl monomer：h-t; h-h; t-tdiene monomer：1,2; 1,4; 3,4stereo-isomerismvinyl monomer：optical isomerism (isotactic, syndiotactic, atactic) diene monomer：geometric isomersequence ofcopolymerrandom copolymerblock copolymergrafting copolymeralternating copolyme

36、rconfiguration1.3 1.3 高分子链的远程结构高分子链的远程结构long-range structure of polymer chainlong-range structure of polymer chain1.3.1 1.3.1 分子量分子量 molecular weightmolecular weightsmall molecule：definite molecular weight for a specific substancepolymer：distribution of molecular weight (polydispersity) for the deta

37、ils, see chapter 4lonly when mw reaches a certain value (critical mw), polymer materials exhibit useful mechanical strength.m polar polymer: dpcri 40m non-polar polymer: dpcri 80strength molecular weightpolarnonpolarl when mw is very high (dp600700),strength reaches a limit, but melt viscosity is to

38、o high to process.plastics and rubber: broad mw distribution (high mw parts contribute to strength, low mw parts improve processability.)fiber: narrow mw distribution1.3.2 1.3.2 内旋转构象内旋转构象 conformational stateconformational staterotation of cc single bond change of conformation larger polymerization

39、 degreetem of bacterias dnathe repeating units in the main chain are connected by covalent bonds no independent motion for single unit polymer chains are poor in entropy.flexibility链段链段 chain segment consisting in many units, which can move independently.considerable conformationldue to presence of

40、h and other substituents, energy barrier must be overcome for rotation of single bond.larger distance smaller repulsion lower energystability: trans gauche cistg-g+cistransgauche正丁烷或聚乙烯正丁烷或聚乙烯内旋转位能图内旋转位能图 for linear pe chain, the energy level of all-trans conformation is the lowestt=0 k: planar zig-

41、zag conformationt 0k: gauche conformation appear due to thermal motion for a with 10,000 bonds,the number of arrangements310,000=104,7711.3.3 1.3.3 分子链的柔顺性分子链的柔顺性 chain flexibilitychain flexibilityl static flexibility (静态柔顺性静态柔顺性) flexibility of polymer chain at thermodynamic equilibrium determined

42、by the difference in the potential energy of trans and gauche conformation ()ktthe polymer chain is rigid.ldynamic flexibility dynamic flexibility (动态柔顺性动态柔顺性) the transition rate between different conformations determined by the energy barrier between different conformations (e) p : time for transi

43、tion from trans to gauche conformation 0exppekte cn co ccm side group polarity interaction flexibility pan pvc ppnumber of polar side group flexibilitypolarity: 1,1- di-substituents size of side group flexibility ps pp pe ch2 ccl2 pvdc ch2 chcl pvcm chain length length of main chain number of confor

44、mation flexibilitylength of side chain interaction flexibilitybut when the side chain is too long, it hinders rotation of the main chain and flexibility decreases.ch3 ch2 c coo(ch2)nch3n: 01219201.4 1.4 高分子链的构象统计高分子链的构象统计conformational statistics of polymer chain1.4.1 1.4.1 自由连接链自由连接链 freely jointed

45、 chainfreely jointed chain freely jointed chain is just used for theoretical calcution, and it does not correspond to any real polymer chain.the polyme chain consists in n equal one-dimensional links of length l (with no occupied volume).there is no restriction on the angles between the links.no ene

46、rgy is required to change the angles. the probability of each bond at any direction is equal and the contour or fully extended length of the chain is nl.other two terms：random walk (无规行走) one-dimensional freely jointed chainrandom flight (无规飞行) three-dimensional freely jointed chainl simulation of f

47、reely jointed chainnn = 10 = 104 4mmthe trace is like that of brownian particles.mthe volume fraction of the units is very small.mthere are lot of holes inside the random coil.l end-to-end distance (末端距),1231.0f jnniirllllll mean-square of end-to-end distance (均方末端距 )2,12312311(.)(. )nnf jijnnijrlll

48、lllllll 2ll liitotal n terms0jil lijthe conformation of freely jointed chain is far from that of extended chain!21 2,f jf jrrn lrnlextended chain22,f jrnlorigin of rubber elasticitymass of unit: micoordinate of ith unit:l radius of gyration (旋转半径 )coordinate of center of massn 时 also applicable to f

49、reely rotating chain and gaussian chainradius of gyration is suitable for polymer chains with multiple chain ends.22(1)(1)/6grnnlnr012i质心质心ri222,1/66gf jrnlr22011ngiirrrn011niirrnirfreely jointed chain2gr1.4.2 1.4.2 自由旋转链自由旋转链freely rotating chainfreely rotating chainmodel with fixed valency angle t

50、he angle are restricted to lie on a cone, but the bond can rotate freely on the surface of the cone. 2,12312311(.)(. )nnf rijnnijrllllllllll l mean-square of end-to-end distance 2ll liitotal n terms221cos(180)cosi illll22cos (180)cosmmi i mlllltotal 2(n-1) termstotal 2(n-m) terms2,f rr=l2n+2(cos+cos

51、2 +cos3 +cosn-1 ) (cos + cos2 +cosn-2 )(cos + + cosn-3 ) +.+ cos 22,21 cos1 cos ()2cos1 cos(1 cos )nf rrlnn22,1 cos1 cosf rrnl222,2f rf jrl nr四面体构型 cos = 1/31.4.3 1.4.3 受阻内旋转链受阻内旋转链hindered rotation chainhindered rotation chainfor a real polymer chain, the rotation of the bonds on the cones is not f

52、ree. energy barrier must be overcome for rotation of the bonds. the energy barrier for rotation is not a constant, but it varies with rotation angle .22,1 cos1cos1cos1cosr rrnlbond angle键角conformation angle构象角 2020cos exp/cosexp/iiukt dukt do(0 )exp(0)1n1oo113.34 1000(120 )( 120 )exp()0.2608.31298j

53、molnnj kmolkfor pe，trans: =0, u(t)=0; gauche (g or g) =120 , u(g or g)=3.34kjmol-1, 298kooo1 cos(0 )0.260 cos(120 )cos( 120 )cos0.4871 0.2600.2601.4.4 1.4.4 高斯链 gaussian chainthe distribution of “equivalent chain” obeys gaussian distribution. gaussian chain(1) the polymer chain comprises n hypotheti

54、cal segments.(2) each segment has a length of l and is rigid.(3) segments are freely jointed and there is no restriction on angles.equivalent freely jointed chain:*the same : =nele2 le=/l*the same contour length: l=nele=nlsin(/2) can be experimentally measured.for pefreely jointed chainfreely rotati

55、ng chainunder conditionextended chainnl22nl26.76nl22/3 n2l2kuhn lengthl (bond length)2.45l8.28 l0.82nlfor freely rotating chain: contour length: nele=nlcos(180-)/2=nlsin(/2) =nele2=2nl2 le=2nl2/nlsin(/2)=2.45l(note: only for freely jointed chain the contour length is nl. for other chains, the contou

56、r length is nlsin(/2).equivalent freely jointed chainobey gaussian distribution; the motion unit is a segment; correspond to real polymer chainfreely jointed chainobey gaussian distribution; the motion unit is a single bond; only used for theoretical study probability distribution function of end-to

57、-end distance for freely jointed chain in one-dimensional space w(x) start from zero point (one end of the chain) each step l (bond length), n steps of random walk (number of bonds) where is the last step (the other end of the chain) located ? end-to-end distance of gaussian chain from statistical m

58、ethod the probability distribution function for other end w(x) is: one end is fixed at x=0, y=0, z=0 p is the probability of the other end located in the space dxdydz z dxdydz x yprobability distribution function in three dimension三维空间几率分布函数三维空间几率分布函数 w(xyz)probability222 222322()3()( )( )( )2222()(

59、)()xp w xyz dxdydzw x dxw y dyw z dzxxedxedyedzxyzdxdydzehedxdydz the probability distribution function in three-dimensional space w(xyz):22222233()()xyzrw xyzee usually only the distance of the ends is cared, and the the direction of the ends is ignored.radiant distribution function w(r)meaning of

60、w(r)： when one end of the chain is fixed at the zero point, w(r) is the probability density for the other end appearing in the spherical shell from radius r to r+dr.rdr22nlr2( )()4w rw xyzr2220()4rr w xyzr dr均方末端距r( )0w rr23nrl08( )3nrrw r drl2220( )rr w r drnl249r 40r 45r l the most probable end-to-end