苏州大学聚合物合成与改性作业答案解析.doc

Chapter 1
1、 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.

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 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 (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 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 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?
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 polymerization and 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 elementary reactions——initiation, 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 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 polymerization 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 whole 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 polymerization 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 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 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-azobisisobutyronitrile) BPO (benzyl peroxide)

KPS (potassium persulfate) cumyl hydroperoxide
14、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 the percentage of coupling and disproportionation
When chain transfer occurs:
l
15、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 specific 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 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 2
1、 What are basic features of living polymerization 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 polymer;
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 radical 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 application of ATRP.
ATRP is a kind of transition metal mediated living radical polymerization, and its mechanism is shown below:
Or
Applications 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 architecture (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 basic 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 copolymer, 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 5
1、 Take Na-naphthalene 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 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, gene delivery, optics, sensors, blood substitution, nanoparticles, and other fields.
4、 Please list three types of dendrimers. What is the repeating unit of Tomalia-type poly(amidoamine) dendrimer?
Tomalia-type poly(amidoamine) (PAMAM)、Newkome’s arborol dendrimers、Phosphorus containing dendrimers、Fréchet-type poly(benzylether).
Repeating unit of PAMAM dendrimers:

5、 Please list the main methods to synthesize dendrimers.
l Divergent synthesis: multiplicative growth from 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 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, multifunctional.
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 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.

Where L is imperfectly branched unit (linear unit), T is terminal unit, and D is perfectly branched unit.

Chapter 6
1、 Please list four types of morphologies of diblock 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: covalent, 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.
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 method 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 copolymer 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) can 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 7
1、 At room temperature, which types of polymers will act as glassy 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(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.
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 to 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 temperature, 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 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, are a special class of elastomers, and a class of copolymers of a physical mix of polymers (hard and soft mers, usua