推荐-苏州大学聚合物合成与改性作业答案

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 there 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.NxMx Mn Nx =∑∑ 2NxM x Mw NxMx =∑∑ 1/1NxM x Mv NxMx αα+⎡⎤=⎢⎥⎢⎥⎣⎦∑∑ Polydispersity of polymers is the exact molecular weight distribution of polymers and lies in the statistical variations present in the polymerization processes. The ratio of the two average molecular weights M w /M n is often useful as a measure of the polydispersity of polymers.2、 Please list the repeating unit of the following polymers and monomers to3、Please list the sources to generate free radicals.Thermal decomposition、photochemical decomposition、oxidation-reduction reaction、high energy particle radiation、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 polymerized via radical, ionic andcoordination polymerizations.●Radical: styrene、vinyl chloride、ethylene、acrylonitrile、methacrylamide;●Ionic: isobutylene、isoprene、iospropyl vinyl ether、styrene；●Coordination: propene、styrene、ethylene、isoprene;6、Can 1,1-diphenylethylene be subjected to polymerization? Why?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、chain 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 polymerizationand 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?● It consists of four elementary reactions ——initiation, propagation,termination, and transfer;● The rate of initiation is the lowest one, which controls the overall rateof polymerization;● Slow initiation, fast propagation, fast termination, and easy termination; ● The products only consists of monomer, polymers (active species, ifpossible);● High polymers exist as the polymerization begins;● Conversion is increased by the extension of polymerization time;● There is no reaction between monomer-monomer, monomer-polymer, andpolymer-polymer;● The concentration of monomer decreases and polymer increases as thepolymerization goes on.12、Notions: efficiency of initiation, kinetic chain length, autoacceleration (geleffect), radical life, polymerization rate, inhibition, retardation.● Efficiency of initiation: the ratio of initiators which are used to initiatepolymerization to initiators that decompose in the whole process of polymerization;● Kinetic chain length: the average number of monomer molecules consumed pereach radical which initiates a polymer chain, and it can be given by the ratio of polymerization rate to initiation rate;[][]2p p p i t t M k M R R v R R k •=== ● Autoacceleration: autoacceleration is a common phenomenon where thepolymerization rate increases for certain period in radical polymerization which is caused by the increase of the system viscosity, thus is also called gel effect;● Radical life: the time from production to termination of radicals;[][][]122s p t s t pM M k M Rt k k R τ••=== ● Polymerization rate: describe how the polymerization concentration orconversion changes with the reaction time, which consists of three elementary reactions —initiation, propagation, and termination, and can be expressed by the following equation:[]p d M dP R dt dt =-= [][]1/21/2()d p p tfk R k I M k = ● Inhibition: a phenomenon in which the reactivity of radicals and stoppedand the polymerization is completely halted due to the addition of inhibitors;● Retardation: a phenomenon in which only a portion of the radicals are stoppedand polymerization occurs at a lower rate and lower polymer molecular weightdue to the addition of retarders;13、Chemical structures: AIBN, BPO, KPS, cumyl hydroperoxide.AIBN (2,2-azobisisobutyronitrile) 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:● Coupling termination: 2Xn v =;● Disproportionation termination: Xn v =;● The two modes coexist: 2v Xn v <<2vXn C D =+ C 、 D represent the percentage of coupling anddisproportionationWhen chain transfer occurs:● [][][][]1(2)2M S I S I a C C C Xn v M M -=+++ 15、Please explain basic principles of dilatometer method.The principles of dilatometer method are based on the linear relationshipbetween the volume contraction and the conversion of the reaction system: 100%m p mV V K V -=⨯ Where m V is the specific volume of monomer, p V 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: 01C%V K V ∆= Where 0V is the original volume of the system, and V ∆denotes the contractionvalue of volume.The dilatometer consists of two parts: the lower part is the reactor, and theupper 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 polymerization systems?●Constant number of polymer chains;●No permanent chain stopping reactions;●Control of chain growth;●Dormant and active states;●Narrow molecular weight distribution;●The plot of Mn versus monomer conversion is linear;●Synthesis of block copolymers, star polymers and comb polymer;●Synthesis of telechelic polymers (control of end groups).2、Please list the main types of “living”/controlled radical polymerization.●Reversible hemolytic cleavage: NMP (nitroxide-mediated polymerization, aspecial kind of SFRP, stable free-radical polymerization) and ATRP (atom transfer radical polymerization);●Chain transfer process: addition fragmentation, RAFT (reversibleaddition-fragmentation chain transfer polymerization), CCTP (catalytic chain transfer polymerization);●Iniferters methods;●Organotellurium and boroxyl-based initiators.3、Please list the basic mechanism and application of ATRP.ATRP is a kind of transition metal mediated living radical polymerization, and its mechanism is shown below:OrApplications of ATRP:●To prepare well-defined macromolecules with predetermined Mw and lowpolydispersity (1.04< Mw/Mn <1.50, 300< Mn <200,000);●To control macromolecular architecture (linear, star, polymer brush,dendritic);●To control microstructure of macromolecules (homopolymer, alternating,block, graft);●To prepare macromonomers and functionalized polymers with COOH, OH, NR1R2and vinyl groups (telechelic, multifunctional, end-functionalized).4、Please list the basic mechanism and application of RAFT polymerization, anddescribe the primary roles of Z and R groups of RAFT agent.Mechanism:Application:●Synthesis of block copolymer, gradient copolymer, and graft copolymer;●Synthesis of polymers with different architectures, like telecheliccopolymer, star copolymer, hyperbranched copolymer, and polymers with network;●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-naphthalene based anionic polymerization of styrene for example, pleasedescribe the basic mechanism and application of living anionic polymerization.Mechanism:Application:●To synthesize a monodisperse polymer;●To measure the anionic polymerization rate;●To prepare a block copolymer;●To prepare a telechelic 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, and often adopts a spherical three-dimensional morphology.Dendrimer has lot of applications: suprachemistry, catalyst, drug delivery, genedelivery, optics, sensors,blood substitution, nanoparticles, and other fields.4、 Please list three types of dendrimers. What is the repeating unit of Tomalia-typepoly(amidoamine) dendrimer?Tomalia-type poly(amidoamine) (PAMAM)、Newkome’s arborol dendrimers 、Phosphorus containing dendrimers 、Fr échet-type poly(benzylether).Repeating unit of PAMAM dendrimers:5、 Please list the main methods to synthesize dendrimers.● Divergent synthesis: multiplicative growth from a central core;● Convergent synthesis: preparation starting from what will become theperiphery of the molecule and progressing inward;● Click chemistry: preparation based on Diels-Alder reactions, thiol-enereactions, and azide-alkyne reactions.6、 By assuming the core functionality is m, and each branching point has threelinking positions, please calculate the surface functionality of dendrimer with generation.*3n n f m =7、 Please describe the advantage of synthesis of dendrimers via orthogonalstrategy.Chemoselective, reduced number of reaction steps, high generation can be achieved, high yield, multifunctional.8、 Please describe the similarity and difference of dendrimer and hyperbranchedpolymer. 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 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 have three kinds of repeating units (DB<1), and their applications are usually coatings. Besides, their synthesis methods are also different.D T DB D T L+=++ 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 diblock copolymers via self-assemblyin 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.●Forces of chemical bonding: covalent, ionic, Van der Waals, hydrogen;●Other forces: magnetic, electrostatic, fluidic;●Polar/Nonpolar: hydrophobicity;●Shape: configurational;●Templates: guided self-assembly;●Kinetic conditions: e.g., diffusion limited.4、Please describe the differences between hairy micelle and crew cut micelle.●Component: when hydrophobic segment is larger than hydrophilic segment, crewcut micelle forms; when hydrophilic segment is larger than hydrophobicsegment, hair micelle forms;●Preparation:⏹Hairy micelle: the block copolymer is directly immersed into selectivesolvents;⏹Crew cut micelle: one method is that the block copolymer is immersedinto cosolvent first, then selective solvent is added slowly withstirring, when the amount of water is up to certain level, thehydrophobic segment combines to form micelle, and dialysis is used toremove cosolvent; the second method is that the block copolymer isdissolved in the mixture of organic solvents and water with differentratio, then selective solvent is added slowly with faster and severeragitation, and dialysis is used to remove the cosolvent;●Shape: for crew cut micelle, different kinds of shapes (spherical, lamellarand others) can be obtained at different conditions; while for hairy micelle, the spherical shape is common;●Investigation and application: the hairy micelle is widely investigated andhas wide applications compared with crew cut micelle.Chapter 71、At room temperature, which types of polymers will act as glassy polymers, rubberyor 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(ethylene 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 affect the crystallizability of polymers.●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);●Cooling rate: slow cooling allows more time for the chains to align;●Annealing: heating to just below the melting temperature can allow chainsto align and form crystals;●Degree of polymerization: it is harder to crystallize longer chains;●Deformation: slow deformation between T g and T m can straighten the chainsallowing them to get closer together.4、Notations: glass transition temperature, melting temperature, thermoplasticelastomer, 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 state—brittleness, stiffness, and rigidity.Melting point: 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, area special class of elastomers, and a class of copolymers of a physical mix ofpolymers (hard and soft mers, usually plastic and rubber) which consist of materials with both thermoplastic and elastomeric properties (recyclable, and do not employ covalent crosslinks);Thermoplastic polymer: a plastic material or polymer (usually linear) that becomes pliable or moldable above a specific temperature and solidifies upon cooling. It can be reshaped by heating and are typically used to produce parts by various polymer processing techniques like injection molding, compression molding, and extrusion;Thermosetting polymer: also known as a thermoset, is a very highly cross-linked polymer that forms a three-dimensional network and irreversible chemical bonds during the curing process. They cannot be reformed once formed.Chapter 81、Please list main types of polyethylene.HDPE(high density), LLDPE(linear low density), LDPE(low density), and high pressure copolymers( AA, VA, MA, EA).2、Notations: filling modification, surface modification, chemical modification.Filling modification: the modification of polymers by adding some inorganic fillings like calcium powder, talcum powder, or silica, to change the properties of polymers or to reduce cost;Surface modification: the act of modifying the surface of a material by bringing physical, chemical, or biological characteristics (roughness, hydrophilicity, surface charge, surface energy, biocompatibility, and reactivity) different from the ones originally found on the surface of a material;Chemical modification: the act of modifying the chemical composition of polymersurfaces by direct chemical reaction with a given solution (wet treatment) or by the covalentbonding of suitable macromolecular chains to the sample surface (grafting).3、What is solution blending? What the features of solution blending?Solution blending is the method of getting blends by adding blending components in the cosolvent with agitation to form uniform solution, followed by heating to remove the solvent, or by nonsolvent coprecipitation. The advantages are that the viscosity of the solution is low when blending, and good performance for systems with good compatibility; the disadvantages are that phase separation occurs when coprecipitating components with poor compatibility, solvent consuming, high cost, and environmentally unfriendly. It applies to polymer systems with cosolvent, blending components that are easily dissolved, investigation for compatibility, and when solution state is directly used. 4、What is blending modification? Please describe its features, classifications,and techniques.Blending modification is the process of mixing of two or more kinds of polymers by physical or/and chemical methods to form macroscopically homogeneous and continuous materials.Features:●It can improve physical and mechanical properties of polymers, like heatresistance, toughness, abrasive resistance, dimensional stability, and someother properties;●It can improve the processability of polymers, like melt fluidity and controlof crystallization behavior of crystalline polymer;●It can reduce the cost on the premise of maintaining its performance;●It can impart some special properties to polymer, like flame resistance,conductivity and damping property.Classifications●Physical blending: melt blending, solution blending, dry powder blending,and emulsion blending;●Chemical blending●Physicochemical blending.Techniques:●Techniques: simple blending(~1950), grafting technique, multilayeremulsion technique(1950~1970), IPN technique, dynamic vulcanizationtechnique, molecular complexation technique, compatilizer technique(1970~), polymer alloy technique (1985~)；●Equipment: banbury mixer, two-roll mill, ball mill, high speed mixer,ribbon-blender.5、Please describe main methods and principles of polymer modification.Methods: blending modification, filling modification, composition modification, chemical modification, and surface modification;Principles:●Adding inorganic or organic materials into polymers through physical andmechanical methods;●Blending different kinds of polymers;●Copolymerization, grafting, blocking, crosslinking of polymers throughchemical methods;●Combination of grafting, blocking, crosslinking, and copolymerization;●To reduce the cost, and impart special properties to materials.Chapter 91、Please describe main polymer processing methods.Extrusion, spinning, coating, injection molding, transfer & compression molding, blow molding & rotational molding, thermoforming, casting, and polymer foaming & shaping.2、What is extrusion molding？How about its features and applications?Definition: a compression process in which the material is forced to flow througha die orifice to provide long, continuous product with regular shape controlledby the orifice shape.Features:●Able to create very complex cross-sections;●Work materials that are brittle;●The extrusion machine forms the basis of nearly all other polymer processes;●Basically involves melting polymer pellets and extruding them out througha two dimensional die;●Produce long, thin products;●Extrusion may be continuous (theoretically producing indefinitely longmaterial) or semicontinuous (producing many species);●The extrusion process can be done with the material hot or cold;●Extrusion defects may occur.Applications:●Food: certain pastas, breakfast cereals, premade cookie dough, some Frenchfries;●Drug carriers: anti-cancer drug Doxorubicin in liposome delivery;●Biomass briquette;●Coating for electrical wire;●Fishing line;●Tubes and bars.3、What is injection molding？How about its features and applications?Definition: a manufacturing process for producing parts by injecting material into a mould.Features:●Injection moulding can be performed with a host of materials, includingmetals, glasses, elastomers, confections, and most commonly thermoplasticand thermosetting polymers;●It the most widely used process;●The injection molding process depends on the injection pressure, injectionvelocity, melt temperature, mold temperature, and holding time;● A high molding speed adapted for mass production is possible;●There is a wide choice of thermoplastic materials providing a variety ofuseful properties;●Short processing cycle and high efficiency;●Automation is easily achieved;●High stability of the products.Applications: wire spools, packaging, bottle caps, pocket combs, storage containers, mechanical parts (including gear), and most other thermoplastic products available.4、What is reaction injection molding？How about its features and applications?Definition: a process of mixing two highly reactive liquids or prepolymers and injected them immediately into the cavity to create thermosets typically of large size.Features:●Production of parts with large size;●Low energy requirement;●Equipment and mold cost are less than injection molding;●Good process reliability;●Wide choice of chemical systems;●Slow cycle times;● A high-density skin is formed with a low-density core.Applications: automotive bumpers, air spoilers, and fenders.（注：可编辑下载，若有不当之处，请指正，谢谢!）。