XX大学聚合物合成与改性作业答案解析.doc

1、Chapter 11、 What are molecular weight and polydispersity of polymers?The molecular weight of polymers is actually the average molecular weight of polymers, which is used to describe the size of polymers and is associated with the properties of polymers, like mechanical strength and viscosity. And th

2、ere are usually three kinds of molecular weight of polymers according to different methods: number-average molecular weight, weight-average molecular weight, and viscosity-average molecular weight. Polydispersity of polymers is the exact molecular weight distribution of polymers and lies in the stat

3、istical variations present in the polymerization processes. The ratio of the two average molecular weights Mw/Mn is often useful as a measure of the polydispersity of polymers.2、 Please list the repeating unit of the following polymers and monomers to synthesize them: PSt、PMMA、PAA、PVA、PIP、PTFE.PSt (

4、polystyrene)PMMA (polymethylmethacrylate)PAA (polyacrylic acid)PVA (polyvinyl alcohol) (imaginary)PIP (polyisoprene)PTFE (polytetrafluroethylene)3、 Please list the sources to generate free radicals.Thermal decomposition、photochemical decomposition、oxidation-reduction reaction、high energy particle ra

5、diation、sonication、plasma initiation、electrolytic initiation.4、 Please list main reactions of radicals.Radical addition reaction、radical coupling reaction、radical disproportionation reaction、radical dissociation reaction、radical transfer reaction.5、 Please list three monomers which can be polymerize

6、d via radical, ionic and coordination polymerizations.l Radical: styrene、vinyl chloride、ethylene、acrylonitrile、methacrylamide;l Ionic: isobutylene、isoprene、iospropyl vinyl ether、styrene；l Coordination: propene、styrene、ethylene、isoprene;6、 Can 1,1-diphenylethylene be subjected to polymerization? Why?

7、No, since the phenyl substitutes groups are bulky which can cause strong steric effects, 1,1-diphenylethylene can only form dimer.7、 Please draw chemical structures of poly(styrene-alt-maleic anhydride). 8、 Please list elemental reactions of chain polymerization.Chain initiation、chain propagation、ch

8、ain termination、chain transfer.9、 Please list the types of microstructures for monosubstituted vinyl monomers.Head-to-tail (1,3-placement, the substitutes are on alternate carbon atoms):Head-to-head (1,2-placement):10、Please list the types of chain transfer reaction in free radical polymerization an

9、d give two examples of chain transfer agents.Chain transfer to monomer, solvent (chain transfer agent), initiator, and polymer;Chain transfer agent: carbon tetrachloride, 1-butanethiol, carbon tetrabromide, triethylamine.11、What are the characteristics of radical polymerization?l It consists of four

10、 elementary reactionsinitiation, propagation, termination, and transfer;l The rate of initiation is the lowest one, which controls the overall rate of polymerization;l Slow initiation, fast propagation, fast termination, and easy termination;l The products only consists of monomer, polymers (active

11、species, if possible);l High polymers exist as the polymerization begins;l Conversion is increased by the extension of polymerization time;l There is no reaction between monomer-monomer, monomer-polymer, and polymer-polymer;l The concentration of monomer decreases and polymer increases as the polyme

12、rization goes on.12、Notions: efficiency of initiation, kinetic chain length, autoacceleration (gel effect), radical life, polymerization rate, inhibition, retardation.l Efficiency of initiation: the ratio of initiators which are used to initiate polymerization to initiators that decompose in the who

13、le process of polymerization;l Kinetic chain length: the average number of monomer molecules consumed per each radical which initiates a polymer chain, and it can be given by the ratio of polymerization rate to initiation rate;l Autoacceleration: autoacceleration is a common phenomenon where the pol

14、ymerization rate increases for certain period in radical polymerization which is caused by the increase of the system viscosity, thus is also called gel effect;l Radical life: the time from production to termination of radicals;l Polymerization rate: describe how the polymerization concentration or

15、conversion changes with the reaction time, which consists of three elementary reactions initiation, propagation, and termination, and can be expressed by the following equation: l Inhibition: a phenomenon in which the reactivity of radicals and stopped and the polymerization is completely halted due

16、 to the addition of inhibitors;l Retardation: a phenomenon in which only a portion of the radicals are stopped and polymerization occurs at a lower rate and lower polymer molecular weight due to the addition of retarders;13、Chemical structures: AIBN, BPO, KPS, cumyl hydroperoxide. AIBN (2,2-azobisis

17、obutyronitrile) BPO (benzyl peroxide) KPS (potassium persulfate) cumyl hydroperoxide14、Please list the relation between degree of polymerization and kinetic chain length.When no chain transfer occurs:l Coupling termination: ;l Disproportionation termination: ;l The two modes coexist: C、D represent t

18、he percentage of coupling and disproportionationWhen chain transfer occurs:l15、Please explain basic principles of dilatometer method. The principles of dilatometer method are based on the linear relationship between the volume contraction and the conversion of the reaction system: Where is the speci

19、fic volume of monomer, is the specific volume of polymer, and K represents the rate of change of volume when the conversion is 100%. The conversion (C%) has a linear relationship with the volume contraction: Where is the original volume of the system, and denotes the contraction value of volume. The

20、 dilatometer consists of two parts: the lower part is the reactor, and the upper one is calibrated capillary. By measuring the volume contraction value at different time, we can get the conversion change with time, and get the polymerization rate.Chapter 21、 What are basic features of living polymer

21、ization systems?l Constant number of polymer chains;l No permanent chain stopping reactions;l Control of chain growth;l Dormant and active states;l Narrow molecular weight distribution;l The plot of Mn versus monomer conversion is linear;l Synthesis of block copolymers, star polymers and comb polyme

22、r;l Synthesis of telechelic polymers (control of end groups). 2、 Please list the main types of “living”/controlled radical polymerization.l Reversible hemolytic cleavage: NMP (nitroxide-mediated polymerization, a special kind of SFRP, stable free-radical polymerization) and ATRP (atom transfer radic

23、al polymerization);l Chain transfer process: addition fragmentation, RAFT (reversible addition-fragmentation chain transfer polymerization), CCTP (catalytic chain transfer polymerization);l Iniferters methods;l Organotellurium and boroxyl-based initiators.3、 Please list the basic mechanism and appli

24、cation of ATRP.ATRP is a kind of transition metal mediated living radical polymerization, and its mechanism is shown below:OrApplications of ATRP:l To prepare well-defined macromolecules with predetermined Mw and low polydispersity (1.04 Mw/Mn 1.50, 300 Mn 200,000);l To control macromolecular archit

25、ecture (linear, star, polymer brush, dendritic);l To control microstructure of macromolecules (homopolymer, alternating, block, graft);l To prepare macromonomers and functionalized polymers with COOH, OH, NR1R2 and vinyl groups (telechelic, multifunctional, end-functionalized).4、 Please list the bas

26、ic mechanism and application of RAFT polymerization, and describe the primary roles of Z and R groups of RAFT agent.Mechanism:Application:l Synthesis of block copolymer, gradient copolymer, and graft copolymer;l Synthesis of polymers with different architectures, like telechelic copolymer, star copo

27、lymer, hyperbranched copolymer, and polymers with network;l Introducing functionalities into polymers.Primary roles of Z and R:Z serves as stabilizing groups, like phenyl, alkyl groups; R serves as reinitiating groups, and should be cleavable, like isopropyl phenyl group.Chapter 51、 Take Na-naphthal

28、ene based anionic polymerization of styrene for example, please describe the basic mechanism and application of living anionic polymerization.Mechanism:Application:l To synthesize a monodisperse polymer;l To measure the anionic polymerization rate;l To prepare a block copolymer;l To prepare a telech

29、elic polymer.2、 Please describe main subclasses of dendritic polymers.Dendrimers、dendrons、hyperbranched polymers、dendrigraft polymers、dendronized polymers.3、 What is dendrimer? How about its main applications?Dendrimer is repetitively branched molecule, which is typically symmetric around the core,

30、and often adopts a spherical three-dimensional morphology.Dendrimer has lot of applications: suprachemistry, catalyst, drug delivery, gene delivery, optics, sensors, blood substitution, nanoparticles, and other fields.4、 Please list three types of dendrimers. What is the repeating unit of Tomalia-ty

31、pe poly(amidoamine) dendrimer?Tomalia-type poly(amidoamine) (PAMAM)、Newkomes arborol dendrimers、Phosphorus containing dendrimers、Frchet-type poly(benzylether).Repeating unit of PAMAM dendrimers:5、 Please list the main methods to synthesize dendrimers.l Divergent synthesis: multiplicative growth from

32、 a central core;l Convergent synthesis: preparation starting from what will become the periphery of the molecule and progressing inward;l Click chemistry: preparation based on Diels-Alder reactions, thiol-ene reactions, and azide-alkyne reactions.6、 By assuming the core functionality is m, and each

33、branching point has three linking positions, please calculate the surface functionality of dendrimer with generation.7、 Please describe the advantage of synthesis of dendrimers via orthogonal strategy.Chemoselective, reduced number of reaction steps, high generation can be achieved, high yield, mult

34、ifunctional.8、 Please describe the similarity and difference of dendrimer and hyperbranched polymer. How to calculate the degree of branching?Similarity: highly branched macromolecules, high solubility in organic solvents, low viscosity, regular structure, high functionalities on the surface of the

35、molecules, Tg is unaffected by molecular structure;Difference: dendrimers are perfectly branched globular macromolecules, and have two kinds of repeating units (DB=1), and their applications are usually drug delivery, gene delivery and sensors; hyperbranched polymers are imperfect dendrimers, and ha

36、ve three kinds of repeating units (DB1), and their applications are usually coatings. Besides, their synthesis methods are also different.Where L is imperfectly branched unit (linear unit), T is terminal unit, and D is perfectly branched unit.Chapter 61、 Please list four types of morphologies of dib

37、lock copolymers via self-assembly in bulk.Spherical, cylindrical, lamellar, and gyroid.2、 Please list three types of morphologies observed in polymer aggregates.Spheres, cylinders, bilayers, and vesicles.3、 Please describe the main driving forces of self-assembly.l Forces of chemical bonding: covale

38、nt, ionic, Van der Waals, hydrogen;l Other forces: magnetic, electrostatic, fluidic;l Polar/Nonpolar: hydrophobicity;l Shape: configurational;l Templates: guided self-assembly;l Kinetic conditions: e.g., diffusion limited.4、 Please describe the differences between hairy micelle and crew cut micelle.

39、l Component: when hydrophobic segment is larger than hydrophilic segment, crew cut micelle forms; when hydrophilic segment is larger than hydrophobic segment, hair micelle forms;l Preparation: n Hairy micelle: the block copolymer is directly immersed into selective solvents;n Crew cut micelle: one m

40、ethod is that the block copolymer is immersed into cosolvent first, then selective solvent is added slowly with stirring, when the amount of water is up to certain level, the hydrophobic segment combines to form micelle, and dialysis is used to remove cosolvent; the second method is that the block c

41、opolymer is dissolved in the mixture of organic solvents and water with different ratio, then selective solvent is added slowly with faster and severer agitation, and dialysis is used to remove the cosolvent;l Shape: for crew cut micelle, different kinds of shapes (spherical, lamellar and others) ca

42、n be obtained at different conditions; while for hairy micelle, the spherical shape is common;l Investigation and application: the hairy micelle is widely investigated and has wide applications compared with crew cut micelle.Chapter 71、 At room temperature, which types of polymers will act as glassy

43、 polymers, rubbery or leathery polymers, and liquid polymers? Please give two individual examples of these polymers.Glass polymers: poly(chlorotrifluroethylene)(PCTFE), polyacrylonitrile (PAN), polystyrene (PS);Rubbery of leathery polymers: polyisobutene(PIB), poly(vinylidene fluoride)(PVDF), poly(e

44、thylene oxide)(PEO);Liquid polymers: polydimethylsiloxane, polybutadiene(PB).2、 Please list three polymers which can crystalline.poly(hexamethylene adipamide)(Nylon-66), poly(vinyl fluoride)(PVF), poly(vinylidene fluoride)(PVDF), poly(tetrafluoroethylene)(PTFE).3、 Please describe the main factors to

45、 affect the crystallizability of polymers.l Complexity of the chain: crystallization is easiest for simple polymers (e.g. polyethylene) and harder for complex polymers (e.g. with large side groups, branches);l Cooling rate: slow cooling allows more time for the chains to align;l Annealing: heating t

46、o just below the melting temperature can allow chains to align and form crystals;l Degree of polymerization: it is harder to crystallize longer chains;l Deformation: slow deformation between Tg and Tm can straighten the chains allowing them to get closer together.4、 Notations: glass transition tempe

47、rature, melting temperature, thermoplastic elastomer, thermoplastic polymer, and thermosetting polymer.Glass transition temperature: the temperature at which the amorphous domains of a polymer take on the characteristic properties of the glassy statebrittleness, stiffness, and rigidity.Melting point

48、: the temperature at which a solid changes state from solid to liquid at atmospheric pressure, and is also the temperature at which the whole macromolecule becomes easily detached and begin to move;Thermoplastic elastomer: sometimes referred to as thermoplastic rubbers, are a special class of elastomers, and a class of copolymers of a physical mix of polymers (hard and soft mers, usua