高分子化学 polymer1 Introduction课件.ppt

1、h1Welcome toh2Content Polymer and its structure Mechanism of polymerization reactions Process of polymerization The reactions of polymerh3Schedule Chapter 1 Introduction 3 hr Chapter 2 Radical Polymerization 12 Chapter 3 Radical Copolymerization6 Chapter 4 Polymerization Process3h4Reference Books 冯新

2、德，高分子合成化学 化学工业出版社，1980。林尚安 等，高分子化学科学出版社，2000。赵德仁，张慰盛，高聚物合成工艺学化学工业出版社，1997。Malcolm P.Stevens“Polymer Chemistry,an Introduction”,3rd ed.,Oxford University Press,1999 George Odian,“Principles of Polymerization”,2nd ed.,John Wiley&Sons,Inc.,New York,1981.http:/ Ih61.Fundamental Conceptsh71.1 What is a p

3、olymer?A polymer is a large molecule comprised of repeating structural units joined by covalently bonds.(Hermann.Staudinger,1924)Poly comes from the Greek word for many and mer comes from the Greek word for parts“.h8methanegasolinewaxpolyethylenecarbonh9Note that all three representations are equiva

4、lent.One usually chooses the representation that emphasizes the monomer(单体单体)from which the polymer was made.There are end groups on the chain that are different from the repeat units,but these usually represent a negligible portion of the molecule,so they are seldom drawn.degree of polymerization聚合

5、度h10Polymer(聚合物)vs Macromolecule(大分子)Macromoleculemolecule with high molecule weightPolymer molecule comprised of repeating unit Sample polymer macromolecule Polyethylene DNA Protein h111.2 Flowchart of Polymeric Materials Inorganic Natural Clays Bricks Cement Pottery Sands Glass Synthetic Fibers Or

6、ganic Natural Polysaccharides Proteins Polyisoprene Synthetic Plastics Fibers Rubbers Adhesive Coatings h12Polymer is everywhereh13Cellulose,Starch,DNA,ProteinIn Nature壳聚糖甲壳素h14Synthetic Materials Annual Production of Polymer Materials(million ton)Year 1970 1980 1990 2000Plastics27 53 107 175(11*)Sy

7、nthetic fiber4.9 12 24 35(6.4)Synthetic rubber5.5 13 23 44(0.9)Total38 78 154 254*Chinah15General Plastics(通用塑料)h16Engineering plastics(工程塑料)h17Synthetic rubber,elastomer(合成橡胶和弹性体)h18Synthetic fibers(合成纤维)Kevlar Vesth19Fine polymers(精细高分子)h20Functional polymers(功能高分子)h21Plastics vs Steelh22Energy Co

8、nsumption h23Green or not?polyolefinIdeal materialpaperglassaluminiumh24NH(CH2)6NHC(CH2)4COOnCH2CHCln1.3.DefinitionsThe degree of polymerization(DP)in a polymer molecule is the number,n,of repeating units in the polymer chain.structural unit结构单元结构单元repeating unit重复单元重复单元unit repeatingmDPMwh25Polymer

9、s are large molecules.Fortunately,they are not random collections of atoms;if this were the case,they would be impossible to study.Polymers are built up from smaller molecules(monomers),and therefore possess a characteristic chain structure consisting of multiple repeat units that are related chemic

10、ally The repeat units can all be identical,in which case the compound is a homopolymer(均聚物均聚物).h26If the repeat units are different,the result is a copolymer(共聚物共聚物).Consider a copolymer made from just two ingredients:the two can be sequenced along the backbone in various modes.交替嵌段无规接枝h27 The chain

11、 itself can have many different topologiesdendrimermacrocycle线型支化交联环状树枝状h28 Nature precise control on molecular structureStarch,Natural rubber,Polysaccharides（多糖）（多糖）Synthetic Various families and large quantities,but less precise1.4 Production of polymerh291.5 Polymer DisciplinesPolymer sciencePoly

12、mer chemistryPolymer physicsPolymer processPolymer materialPolymerization engineeringh30Polymer Chemistry Content Polymer and its structure Polymerization mechanism and kinetics Polymer reaction Frontier Novel synthetic method and polymer family Design and control on the chain structure of polymer R

13、ecycle of polymerh312.Categories and Nomenclature of Polymerh322.1 Classification Rules There is no uniform system of classification of polymers.The terminology has evolved along with polymer science,and there are numerous exceptions to categories.The way people classify polymers depends their exper

14、ience.Widely used historical terms or trade names lacking information content.h33A:ApplicationPlasticsFibersRubbersCoatingsAdhensivesIndustry PolymerFunctionalGeneralFineh34B.Processability A thermosetting(热固性)plastic,or thermoset,solidifies or sets irreversibly when heated.Elastomers(弹性体)are rubber

15、y polymers that can be stretched easily to several times their unstretched length and which rapidly return to their original dimensions when the applied stress is released.Molecules in a thermoplastic(热塑性）are held together by relatively weak intermolecular forces,so that the material softens when ex

16、posed to heat and then returns to its original condition when cooled无定形结晶h35C:Chemical Composition Carbon-chain polymer backbone composed of carbon atom Hetero chain polymer composed of both carbon and other atoms,e.g.O,N,S,P etc.Element polymer no carbon in backboneCCCCCCCOCCOS iOS iC H3C H3C H3C H

17、3OS iOC H3C H3h36Carbon chain Polymer(碳链高分子碳链高分子)Vinyl polymersa.Polyolefin(聚烯烃):polymer derived from alkenePolyethylene(聚乙烯),polypropylene(聚丙烯),etc b.Polystyrene:PS(聚苯乙烯,1839 by Eduard Simon)and its families(ABS，SBS，SBR)；c.Polyvinylchloride：PVC(聚氯乙烯,1872 by Eugen Baumann)and its copolymers,d.Acryli

18、c polymers:PMMA(聚甲基丙烯酸甲酯),PA(聚丙烯酸),;f.Polydiene:synthetic rubber,PBd(聚丁二烯),PIp(聚异戊二烯),h37Heterochain polymer(杂链高分子)Polyamide/Nylon(聚酰胺),Polyurethane(聚氨酯)Polyurea(聚脲)Polysulfone(聚砜),Phenolic(酚醛),Ureas(脲醛)聚酯聚醚聚酰亚胺h38Element chain polymer(元素高分子元素高分子)PolysiliconeS iOS iC H3C H3C H3C H3OS iOC H3C H3h392.

19、2 NomenclaturePolymer nomenclature is complicated for a variety of reasons:Most polymer names are based on the names of monomer(source-based system)IUPAC system is not widely used Some polymer structures are so complicated:branching or crosslinking;Polymer science has some fairly sharp defined bound

20、aries:rubber chemist vs plastic chemist;Describe polymer based on its characteristicsh40A.According to the name of monomer-vinyl polymersHomopolymer:poly(monomer)polystyrene,PS;poly(methyl methacrylate),PMMACopolymer:poly(monomer-co-monomer)poly(ethylene-co-propylene),乙烯-丙烯共聚物poly(ethylene-r-propyle

21、ne),乙烯-丙烯无规共聚物poly(ethylene-b-propylene),乙烯-丙烯嵌段共聚物poly(ethylene-g-propylene),乙烯-丙烯接枝共聚物poly(ethylene-a-styrene),乙烯-苯乙烯交替共聚物h41B.According to the functional group in the repeat unit(condensation polymer)Polyester;polyether,polyamide NH(CH2)6NHCO(CH2)4CO()nOCH2CH2OCOCO()n poly(hexamethyleneadipamide)

22、(聚己二酰己二胺)Poly(ethylene terephthalate)聚对苯二甲酸乙二醇酯h42C According to the monomer employedphenol-formaldehyde resin 酚醛树脂(苯酚+甲醛)epoxy resin 环氧树脂(双酚A+环氧氯丙烷)D.IUPAC system poly(oxyethylene)poly(ethylene oxide)polymethylene polyethylene(CH2CH2O)nh43E Slang and Trade Names These slang names often contain vest

23、iges of the chemical description of the polymer,but shortened or corrupted.The trade names have short,snappy-sounding names that could be easily remembered and spelled by their customers.Nylon 6 polycaprolactam(聚己内酰胺)EPR ethylene-propylene rubberF AbbreviationsLDPE low density polyethylenePVC polyvi

24、nylchloridePET poly(ethylene terephthalate)h443.Polymerization Reactionh453.1 Condensation(缩合)vs.Addition(加成)Carothers originally classified polymers based on a comparison of the atoms in the monomer to the atoms in the repeat unit.Addition polymerization（加成聚合）（加成聚合）Polymer has the same atoms as the

25、ir monomers Condensation polymerization（缩合聚合）（缩合聚合）polymer has fewer atoms in the repeat unit(i.e.,some small molecule was emitted during polymerization).COOHHOOCHOCH2CH2OHCOOCH2CH2OOCn+H2O+nnnnnh46 Condensation or Addition?COORCOORHORCOOHCOORH2O+nnh473.2 Chain(连锁)vs Step(逐步)Polymerization reactions

26、 are characterized according to its mechanism Chain polymerization（连锁聚合）（连锁聚合）The molecular weight increases by the successive and fast linking of monomer molecules to the end of a growing chain.Step Polymerization（逐步聚合）（逐步聚合）Polymer chain are built up in a stepwise fashion by the random union of mo

27、nomer molecules to form dimers,trimers and higher species throughout the monomer matrix h48Comparison between Chain and Step PolymerizationChain Stepmonomerpolymerh49Differences between Chain and Step PolymerizationGrowth occurs only by addition of monomer to active chain end.Monomer is present thro

28、ughout,but its concentration decreases.Polymer begins to form immediately.Chain growth is usually very rapid(second to microseconds).MW and yield depend on mechanism details.Only monomer and polymer are present during reaction.Usually(but not always)polymer repeat unit has the same atoms as had the

29、monomer Any two molecular species can react.Monomer disappears early.Polymer MW rises slowly.Growth of chains is usually slow(minutes to days).Long reaction times increase MW,but yield of polymer hardly changes.All molecular species are present throughout.Usually(but not always)polymer repeat unit h

30、as fewer atoms than had the monomer.ChainSteph50Variation of Conversion and MWStepchaintime conversion(%)timestepchainMnh51There are far too many exceptions.Step polymerization by addition of alcohols to diisocyanates to form polyurethanes:Chain polymerization(ring opening of heterocycle)with loss o

31、f CO2 to form polypeptide.h52Other terminologies Ring-opening polymerization(开环聚合)Ring-opening Metathesis polymerization(开环异位聚合)Group transfer Polymerization(基团转移聚合)h533.3 Homogeneous vs heterogeneous bulk(本体本体)solution(溶液溶液)emulsion(乳液乳液)dispersion(分散分散)precipitation(沉淀沉淀)suspension(悬浮悬浮)surface(表面

32、表面)solid state(固相固相)h544.Molecular Weight and Molecular Weight Distributionh554.1 Molecular Weight Distribution(分子量分布分子量分布)Because all polymers are mixtures of many large molecules(polydispersity),one must resort to averages to describe molecular weight.h56/11iiiiMNMNM4.2 Average Molecular Weight(平均

33、分子量)Among many possible ways of reporting averages,four are commonly used:Viscosity Average 23iiiizMNMNMZ AverageiiinNMNMNumber AverageiiiiwMNMNM2Weight AverageMMzMwMMn1qqiiiiMNMNMAveragenwMMPDIh57The weight average is probably the most useful,because it fairly accounts for the contributions of diff

34、erent sized chains to the overall behavior of the polymer,and correlates best with most of the physical properties of interest,e.g.melt viscosity.The ratio of Mw to Mn is known as the polydispersity index(PDI,多分散性指数),and provides a rough indication of the breadth of the distribution.The PDI approach

35、es 1.0(the lower limit)for special polymers with very narrow MW distributions,but,for typical commercial polymers,is typically greater than 2(occasionally much greater).h58Small molecules have small valuesthere is a sharp rise in properties as the chains grow to intermediate sizethe properties level

36、 off as the chains become long enough to be true polymers4.3 Dependence of Polymer Properties on MWh59 Many polymer properties of interest(Tg,modulus,tensile strength,etc.)follow a peculiar pattern with increasing MW.The goal of polymer synthesis is not to make the largest possible molecules,but rat

37、her,to make molecules large enough to get onto the plateau region.A few properties are dictated by the repeat units alone,and therefore these are not changed much by MW.Examples:color,dielectric constant,and refractive index.h605.Polymer Structureh61Structure unitMonomer sequence -AABBBABABBABB-AAAA

38、ABBBBBBBB-Stereoregularity（立构规整性）（立构规整性）Topology（拓朴结构）（拓朴结构）CH2CCH3CH3CH2CHCH2CH3CH2CHCH2CHCH2CHClClClCH2CHClCHCH2ClCHCH2ClRRRRRRRRRR5.1 Chain Structureisotacticsyndiotacticcistranshead-headhead-tailh625.2 Conformation(构象)random coilrigid rodhelicalhexagonalh635.3 Aggregation Morphology(聚集态结构)Most s

39、mall molecule behavior can be understood in terms of three states:gas,liquid,and solid.Polymers are large molecules with strong intermolecular force and tangled chains,and do not have a vapor phase.The length of polymer molecules also makes it difficult for the large crystals found in the solid phas

40、es of most small molecules to form.Instead solid polymers can be modeled in terms of two phases-crystalline and amorphous.Thus the behavior of polymers can better be understood in term of the three phases:melt(熔融熔融),crystalline(结晶结晶),and amorphous(无定形无定形)h64Crystalline Polymer molecules are very lar

41、ge so it might seem that they could not pack together regularly and form a crystal.It now is known that regular polymers may form lamellar(plate-like片晶)crystals with a thickness of 10 to 20 nm.When a molten crystallizable polymer cools,the crystals grow from individual nuclei and radiate out like th

42、e spokes of a bicycle wheel.The crystalline portions actually radiate out in in three dimensions,forming spheres that are called spherulites（球晶）（球晶）.h65Amorphous(无定型无定型)Amorphous polymers are softer,and are penetrated more by solvents than are their crystalline counterparts.Polymer chains with branc

43、hes or irregular pendant groups cannot pack together regularly enough to form crystals.These polymers are said to be amorphous.h66Semi-crystalline Semi-crystalline polymers have both crystalline and amorphous regions.Semi-crystallinity is a desirable property for most plastics because they combine t

44、he strength of crystalline polymers with the flexibility of amorphous.Semi-crystalline polymers can be tough with an ability to bend without breakingIf we model a polymer as having distinct crystalline and amorphous regions,then the percentage of the polymer that is crystalline is called the percent

45、 crystallinity.The percent crystallinity has an important influence on the properties of the polymer.h67Aggregation Morphology(聚集态形态)Liqid crystallineOrientationh68Aggregation MorphologyBlend PS-b-PIp(PS-b-PnBA)nX共混物h696.Important Propertiesh70Mechanical properties:Tensile strength,Impact resistant,

46、etcProcessing properties:melt viscosity Thermal stability:Tg,Tm,TcFlame resistanceChemical resistanceDegradabilityOthersh71Tensile Strength(拉伸强度)stress needed to break a sampleh72%Elongation to Break(断裂伸长率)Fibers have a low elongation-to-break and elastomers have a high elongation-to-breakstrain on

47、a sample when it breaksh73Youngs Modulus(杨氏模量)Rigid materials,such as metals,have a high Youngs modulus.In general,fibers have high Youngs modulus values,elastomers have low values,and plastics lie somewhere in betweenYoungs modulus is the ratio of stress to strain.It also is called the modulus of e

48、lasticity or the tensile modulush74Toughness(韧性)There is a difference between toughness and strength,as is illustrated in the three plots.The toughness is a measure of the energy a sample can absorb before it breaksh75The Glass Transition(玻璃化转变)At a low temperature the amorphous regions of a polymer

49、 are in the glassy state.In this state the molecules are frozen on place.They may be able to vibrate slightly,but do not have any segmental motion in which portions of the molecule wiggle around.In the glassy state,the motion of the red molecule in the schematic diagram at the right would NOT occur.

50、When the amorphous regions of a polymer are in the glassy state,it generally will be hard,rigid,and brittle.h76Melting Point(熔点)Polymers do not have a single well-defined melting point.When a polymer melts it slowly becomes leathery,then tacky,and then liquid over a fairly broad temperature range.Th