1、1,Polymer Chemistry,高分子化学,Welcome to,2,Content,Polymer and its structure Mechanism of polymerization reactions Process of polymerization The reactions of polymer,3,Schedule,Chapter 1 Introduction 3 hr Chapter 2 Radical Polymerization 12 Chapter 3 Radical Copolymerization 6 Chapter 4 Polymerization P
2、rocess 3,4,Reference Books,冯新德，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
3、:/ I,6,1. Fundamental Concepts,7,1.1 What is a polymer?,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“.,8,methane,gasoline,wax,polyethy
4、lene,carbon,9,Note that all three representations are equivalent. One usually chooses the representation that emphasizes the monomer (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 th
5、e molecule, so they are seldom drawn.,degree of polymerization 聚合度,10,Polymer(聚合物) vs Macromolecule(大分子),Macromolecule molecule with high molecule weight Polymer molecule comprised of repeating unit,Sample polymer macromolecule Polyethylene DNA Protein ,11,1.2 Flowchart of Polymeric Materials,Inorga
6、nic Natural Clays Bricks Cement Pottery Sands Glass Synthetic Fibers,Organic Natural Polysaccharides Proteins Polyisoprene Synthetic Plastics Fibers Rubbers Adhesive Coatings,12,Polymer is everywhere,13,Cellulose, Starch, DNA, Protein,In Nature,壳聚糖,甲壳素,14,Synthetic Materials,Annual Production of Pol
7、ymer Materials (million ton)Year 1970 1980 1990 2000 Plastics 27 53 107 175(11*) Synthetic fiber 4.9 12 24 35 (6.4) Synthetic rubber 5.5 13 23 44 (0.9) Total 38 78 154 254 * China,15,General Plastics(通用塑料),16,Engineering plastics(工程塑料),17,Synthetic rubber, elastomer (合成橡胶和弹性体),18,Synthetic fibers(合成
8、纤维),Kevlar Vest,19,Fine polymers(精细高分子),20,Functional polymers(功能高分子),21,Plastics vs Steel,22,Energy Consumption,23,Green or not?,24,1.3. Definitions,The 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,repeating unit
9、 重复单元,25,Polymers 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
10、that are related chemically,The repeat units can all be identical, in which case the compound is a homopolymer(均聚物).,26,If the repeat units are different, the result is a copolymer(共聚物). Consider a copolymer made from just two ingredients: the two can be sequenced along the backbone in various modes
11、.,交替,嵌段,无规,接枝,27,The chain itself can have many different topologies,dendrimer,macrocycle,线型,支化,交联,环状,树枝状,28,Natureprecise control on molecular structure Starch, Natural rubber, Polysaccharides（多糖）Synthetic Various families and large quantities, but less precise,1.4 Production of polymer,29,1.5 Poly
12、mer Disciplines,Polymer science,Polymer chemistry,Polymer physics,Polymer process,Polymer material,Polymerization engineering,30,Polymer Chemistry,ContentPolymer and its structurePolymerization mechanism and kineticsPolymer reactionFrontier Novel synthetic method and polymer family Design and contro
13、l on the chain structure of polymerRecycle of polymer,31,2. Categories and Nomenclature of Polymer,32,2.1 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 peo
14、ple classify polymers depends their experience.Widely used historical terms or trade names lacking information content.,33,A: Application,Plastics,Fibers,Rubbers,Coatings,Adhensives,Industry Polymer,Functional,General,Fine,34,B. Processability,A thermosetting(热固性) plastic, or thermoset, solidifies o
15、r “sets“ irreversibly when heated.,Elastomers(弹性体) are rubbery 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
16、weak intermolecular forces, so that the material softens when exposed to heat and then returns to its original condition when cooled,无定形,结晶,35,C: Chemical Composition,Carbon-chain polymer backbone composed of carbon atomHetero chain polymer composed of both carbon and other atoms, e.g. O, N, S, P et
17、c.Element polymer no carbon in backbone,36,Carbon chain Polymer(碳链高分子),Vinyl polymers a. Polyolefin (聚烯烃) : polymer derived from alkene Polyethylene(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 E
18、ugen Baumann) and its copolymers, d. Acrylic 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),37,Heterochain 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,38,Element chain polymer(
19、元素高分子),Polysilicone,39,2.2 Nomenclature,Polymer 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 s
20、ome fairly sharp defined boundaries: rubber chemist vs plastic chemist;,Describe polymer based on its characteristics,40,A. According to the name of monomer-vinyl polymersHomopolymer: poly(monomer)polystyrene, PS; poly(methyl methacrylate), PMMACopolymer: poly(monomer-co-monomer)poly(ethylene-co-pro
21、pylene),乙烯-丙烯共聚物poly(ethylene-r-propylene),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,41,B. According to the functional group in the repeat unit (condensation polymer)Polyester; polyether, polyamide,poly(hexamethyleneadipa
22、mide) (聚己二酰己二胺),Poly(ethylene terephthalate) 聚对苯二甲酸乙二醇酯,42,C 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 systempoly(oxyethylene) poly(ethylene oxide)polymethylene polyethylene,43,E Slang and Trade Names These slang names often contain ves
23、tiges 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 po
24、lyvinylchloridePET poly(ethylene terephthalate),44,3. Polymerization Reaction,45,3.1 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）Polymer has the same atoms
25、as their monomersCondensation polymerization （缩合聚合）polymer has fewer atoms in the repeat unit (i.e., some small molecule was emitted during polymerization).,46,Condensation or Addition ?,47,3.2 Chain(连锁) vs Step(逐步),Polymerization reactions are characterized according to its mechanismChain polymeriz
26、ation （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）Polymer chain are built up in a stepwise fashion by the random union of monomer molecules to form dimers, trimers and higher species throughout t
27、he monomer matrix,48,Comparison between Chain and Step Polymerization,Chain Step,monomer,polymer,49,Differences between Chain and Step Polymerization,Growth occurs only by addition of monomer to active chain end. Monomer is present throughout, but its concentration decreases. Polymer begins to form
28、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 monomer,Any two molecular species can react. Monomer di
29、sappears 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 has fewer atoms than had the monomer.,Chain,St
30、ep,50,Variation of Conversion and MW,51,There are far too many exceptions. Step polymerization by addition of alcohols to diisocyanates to form polyurethanes: Chain polymerization (ring opening of heterocycle) with loss of CO2 to form polypeptide.,52,Other terminologies,Ring-opening polymerization (
31、开环聚合) Ring-opening Metathesis polymerization(开环异位聚合) Group transfer Polymerization(基团转移聚合),53,3.3 Homogeneous vs heterogeneous,bulk (本体) solution (溶液) emulsion (乳液) dispersion (分散) precipitation (沉淀) suspension (悬浮) surface (表面) solid state (固相),54,4. Molecular Weight and Molecular Weight Distributi
32、on,55,4.1 Molecular Weight Distribution(分子量分布),Because all polymers are mixtures of many large molecules (polydispersity), one must resort to averages to describe molecular weight.,56,4.2 Average Molecular Weight(平均分子量),Among many possible ways of reporting averages, four are commonly used:,Viscosit
33、y Average,M,MzMwMMn,Average,57,The weight average is probably the most useful, because it fairly accounts for the contributions of different 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 M
34、w 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 approaches 1.0 (the lower limit) for special polymers with very narrow MW distributions, but, for typical commercial polymers, is typically greater than 2 (occasiona
35、lly much greater).,58,Small molecules have small values,there is a sharp rise in properties as the chains grow to intermediate size,the properties level off as the chains become long enough to be true polymers,4.3 Dependence of Polymer Properties on MW,59,Many polymer properties of interest (Tg, mod
36、ulus, tensile strength, etc.) follow a peculiar pattern with increasing MW. The goal of polymer synthesis is not to make the largest possible molecules, but rather, to make molecules large enough to get onto the plateau region. A few properties are dictated by the repeat units alone, and therefore t
37、hese are not changed much by MW. Examples: color, dielectric constant, and refractive index.,60,5. Polymer Structure,61,Structure unitMonomer sequence-AABBBABABBABB- -AAAAABBBBBBBB-Stereoregularity （立构规整性）Topology （拓朴结构）,5.1 Chain Structure,isotactic,syndiotactic,cis,trans,head-head,head-tail,62,5.2
38、 Conformation(构象),random coil,rigid rod,helical,hexagonal,63,5.3 Aggregation Morphology(聚集态结构),Most small 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 ph
39、ase. The length of polymer molecules also makes it difficult for the large crystals found in the solid phases 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 t
40、he three phases: melt(熔融), crystalline(结晶), and amorphous (无定形),64,Crystalline,Polymer molecules are very large 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 2
41、0 nm.,When a molten crystallizable polymer cools, the crystals grow from individual nuclei and radiate out like the spokes of a bicycle wheel. The crystalline portions actually radiate out in in three dimensions, forming spheres that are called spherulites （球晶）.,65,Amorphous (无定型),Amorphous polymers
42、 are softer, and are penetrated more by solvents than are their crystalline counterparts.,Polymer chains with branches or irregular pendant groups cannot pack together regularly enough to form crystals. These polymers are said to be amorphous.,66,Semi-crystalline,Semi-crystalline polymers have both
43、crystalline and amorphous regions. Semi-crystallinity is a desirable property for most plastics because they combine the strength of crystalline polymers with the flexibility of amorphous. Semi-crystalline polymers can be tough with an ability to bend without breaking,If we model a polymer as having
44、 distinct crystalline and amorphous regions, then the percentage of the polymer that is crystalline is called the percent crystallinity. The percent crystallinity has an important influence on the properties of the polymer.,67,Aggregation Morphology(聚集态形态),Liqid crystallineOrientation,68,Aggregation
45、 Morphology,Blend,PS-b-PIp,(PS-b-PnBA)nX,共混物,69,6. Important Properties,70,Mechanical properties: Tensile strength, Impact resistant, etc Processing properties: melt viscosity Thermal stability: Tg , Tm, Tc Flame resistance Chemical resistance Degradability Others,71,Tensile Strength(拉伸强度),stress ne
46、eded to break a sample,72,% Elongation to Break(断裂伸长率),Fibers have a low elongation-to-break and elastomers have a high elongation-to-break,strain on a sample when it breaks,73,Youngs Modulus(杨氏模量),Rigid materials, such as metals, have a high Youngs modulus. In general, fibers have high Youngs modul
47、us values, elastomers have low values, and plastics lie somewhere in between,Youngs modulus is the ratio of stress to strain. It also is called the modulus of elasticity or the tensile modulus,74,Toughness(韧性),There is a difference between toughness and strength, as is illustrated in the three plots
48、.,The toughness is a measure of the energy a sample can absorb before it breaks,75,The Glass Transition(玻璃化转变),At a low temperature the amorphous regions of a polymer 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. When the amorphous regions of a polymer are in the glassy state, it generally will be hard, rigid, and brittle.,
