苏州大学聚合物合成与改性作业答案解析.doc
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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
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