6.3 Techniques of Free Radical Polymerization.
6.4 Kinetic and Mechanism of polymerization.
6.5 Stereochemistry of polymerization.
6.6 Polymerization of Dienes
6.7 Monomer Reactivity
6.8 Copolymerization.
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Free Radical Polymerization презентация
Содержание
- 2. A. Type of polymerization. 6. 1
- 3. B. Commercialized free-radical polymerization.
- 4. 6.2 Free Radical Initiators. 6.2.1 Peroxides
- 5. d. Other peroxides. Diacetyl peroxide
- 6. e. Promoters : Inducing initiation at lower
- 7. B. Hydroperoxide a.
- 8. A. α,α'-Azobis(isobutyronitrile) (AIBN).
- 9. B. Side reaction : Cage effect.
- 10. A. One electron transfer reaction.
- 11. A. Peroxide and Azo compound.
- 12. A. Polymerization without initiators.
- 13. 6.2.6 Electrochemical Polymerization. A. Polymerization of
- 14. 6.3 Techniques of Free Radical Polymerization.
- 15. 6.3 Techniques of Free Radical Polymerization.
- 16. 6.3.2 Suspension. A. Reactor charges.
- 17. 6.3.3 Solution. A. Reactor charges.
- 18. 6.3.4 Emulsion. A. Reactor charges.
- 19. 6.3.4 Emulsion. TABLE 6.3. Typical
- 20. 6.4 Kinetic and Mechanism of polymerization.
- 21. b. Propagation. (6.26) 1) Head-to-tail orientation
- 22. c. Termination. 1)
- 23. 2) Disproportionation. Poly(methyl methacrylate) radical.
- 24. B. Kinetic of free
- 25. c. Termination rate ( Rt )
- 26. e. Average kinetic chain length (
- 27. f. Gel effect : Trommsdorff effect, Norris-smith
- 28. by hydrogen abstracting. Lowering average kinetic
- 29. c. Moving to initiators or monomers.
- 30. e. Moving to chain transfer agent.
- 31. a. Copper(I) bypyridyl(bpy) complex:
- 32. c. Synthesis of block copolymers like anionic
- 33. 6.5 Stereochemistry of polymerization.
- 34. B. Factors influencing stereochemistry in free-radical polymerization.
- 35. c. Terminal carbon : sp2( planar )
- 36. 6.6.1 Isolated Dienes
- 37. A. Structure of conjugated Diene monoer.
- 38. C. 1,4-Addition : Delocalized double bond
- 39. TABLE 6.6 Structure of Free Radical-Initiated Diene
- 40. F. s-cis and s-trans 6.6.2 Conjugated Dienes.
- 41. A. Thermodynamic feasibility.
- 42. 6.7 Monomer Reactivity
- 43. B. Factors of monomer reactivity in free
- 44. C. The inverse relationship between monomer stability
- 45. D. Ceiling temperature (Tc)
- 46. A. Mechanism of copolymerization. 6.8 Copolymerization.
- 47. a. b.
- 48. a. r1 = r2
- 49. D. Alfrey-price Q-e scheme.
- 50. E. Charge transfer complex polymerization(alternating copolymer).
- 51. b. c. E. Charge transfer complex polymerization (alternating copolymer). (6.58) (6.57)
A. Type of polymerization. 6. 1 Introduction Free-radical polymerization Ionic polymerization Complex coordination polymerization
Слайд 1
Chapter 6. Free Radical Polymerization
6.1 Introduction
6.2 Free Radical Initiators.
Слайд 2A. Type of polymerization.
6. 1 Introduction
Free-radical polymerization
Ionic polymerization
Complex coordination
polymerization
Слайд 46.2 Free Radical Initiators.
6.2.1 Peroxides and Hydroperoxides
A.
Benzoly peroxide and other peroxides
a. Thermal decomposition of BPO.
a. Thermal decomposition of BPO.
b. Half-life of benzoyloxy radical : 30 min at 100℃
c. Cage effect : confining effect of solvent molecules.
Слайд 5d. Other peroxides.
Diacetyl peroxide Di-t-butyl peroxide
Diacetyl peroxide Di-t-butyl peroxide
(half-life:10hours at 120℃)
6.2.1 Peroxides and Hydroperoxides
Слайд 6e. Promoters : Inducing initiation at lower temperature.
(6.9)
(6.10)
+
+
+
-
6.2.1 Peroxides and
Hydroperoxides
Слайд 7B. Hydroperoxide
a. Thermal decomposition hydroperoxide
b. Cumyl hydroperoxide.
6.2.1 Peroxides and Hydroperoxides
Слайд 8
A. α,α'-Azobis(isobutyronitrile) (AIBN).
a. Decomposition of AIBN.
b. Half-life of
isobutyronitrile radical : 1.3 hours at 80℃.
6.2.2 Azo Compounds.
Слайд 9B. Side reaction : Cage effect.
a. Tetramethylsuccinonitrile
b. Ketenimine
6.2.2 Azo Compounds.
Слайд 10 A. One electron transfer reaction.
a.
Making free radical by one electron transfer by redox reaction.
b. Low-temperature reaction.
c. Emulsion polymerization.
b. Low-temperature reaction.
c. Emulsion polymerization.
B. Example of redox system.
6.2.3 Redox Initiators.
Слайд 11
A. Peroxide and Azo compound.
Photolysis
and thermalysis.
B. Photolabile initiator.
6.2.4 Photoinitiator
Слайд 12A. Polymerization without initiators.
a. Dimer formation by Diels-Alder
reation.
11
12
·
b. Radical formation from dimer.
·
6.2.5 Thermal Polymerization.
Слайд 136.2.6 Electrochemical Polymerization.
A. Polymerization of electrolysis.
a. Cathode
reaction :
electron transfer to monomer ion forming radical anion (6.22)
b. Anode reaction :
electron transfer to anode forming radical cation (6.23)
B. Coating metal surfaces with polymers.
electron transfer to monomer ion forming radical anion (6.22)
b. Anode reaction :
electron transfer to anode forming radical cation (6.23)
B. Coating metal surfaces with polymers.
Слайд 15 6.3 Techniques of Free Radical Polymerization.
6.3.1 Bulk
A. Reactor charges.
a. Monomer.
b. Initiator (soluble in monomer).
B. Problems.
a. Heat transfer.
b. Viscosity.
c. Auto-acceleration.
Слайд 16 6.3.2 Suspension.
A. Reactor charges.
a. Monomer.
b. Initiator (soluble
in monomer).
c. Water or other liquid.
d. Stabilizer: Poly(vinyl alcohol), CMC
B. Vigorously stirring to keep suspension.
c. Water or other liquid.
d. Stabilizer: Poly(vinyl alcohol), CMC
B. Vigorously stirring to keep suspension.
Слайд 176.3.3 Solution.
A. Reactor charges.
a. Monomer (soluble in
solvent).
b. Initiator (soluble in solvent).
c. Solvent.
B. Refluxing solution.
b. Initiator (soluble in solvent).
c. Solvent.
B. Refluxing solution.
Слайд 18 6.3.4 Emulsion.
A. Reactor charges.
a. Monomer.
b. Redox initiator
c. Soap or emulsifier.
d. Water.
e. Others (cf. Table 6.3).
B. Polymerization in swollen micelle.
Latex products.
Слайд 19
6.3.4 Emulsion.
TABLE 6.3. Typical Emulsion Polymerization Recipesa
Ingredients, Conditions
Ingredients (parts by
weight)
Water
Butadiene
Styrene
Ethyl acrylate
2-Chloroethyl vinyl ether
p-Divinylbenzene
Soap
Potassium persulfate
1-Dodecanethiol
Sodium pyrophosphate
Conditions
Time
Temperature
Yield
Water
Butadiene
Styrene
Ethyl acrylate
2-Chloroethyl vinyl ether
p-Divinylbenzene
Soap
Potassium persulfate
1-Dodecanethiol
Sodium pyrophosphate
Conditions
Time
Temperature
Yield
aRecipes from Cooper.23
bSodium lauryl sulfate.
190
70
30
-
-
-
5
0.3
0.5
-
12hr
50oC
65%
Styrene-Buradiene
Copolymer
Polyacrylate
Latex
133
-
-
93
5
2
3b
1
-
0.7
8hr
60oC
~100%
Слайд 206.4 Kinetic and Mechanism of polymerization.
A. Mechanism of free-radical polymerization.
a. Initiation.
1) Decomposition.
Initiator → 2R․
2) Addition.
(6.25)
Слайд 21b. Propagation.
(6.26)
1) Head-to-tail orientation : predominant reaction.
Steric and electronic
effects.
2) Examples of not exclusively head-to-tail orientation.
2) Examples of not exclusively head-to-tail orientation.
(13-17% of head to head) (5-6% of head to head) (19% of head to head)
6.4 Kinetic and Mechanism of polymerization.
Слайд 22 c. Termination.
1) Combination.
(6.27)
Polystyrene radical.
(6.29)
6.4 Kinetic and
Mechanism of polymerization.
Слайд 23 2) Disproportionation.
Poly(methyl methacrylate) radical.
① Repulsion of ester
group.
② Easy alpha hydrogen abstraction.
3) Acrylonitrile : Combination virtually exclusively at 60℃.
4) Poly(vinyl acetate) : Disproportionation.
② Easy alpha hydrogen abstraction.
3) Acrylonitrile : Combination virtually exclusively at 60℃.
4) Poly(vinyl acetate) : Disproportionation.
6.4 Kinetic and Mechanism of polymerization.
Слайд 24 B. Kinetic of free radical polymerization.
a. Assumption.
1) The rates of initiation, propagation, and termination are all different.
2) Independent of chain length.
3) Negligible end group.
4) At steady state, constant radical concentration.
(steady state assumption)
1) The rates of initiation, propagation, and termination are all different.
2) Independent of chain length.
3) Negligible end group.
4) At steady state, constant radical concentration.
(steady state assumption)
b. Initiation (Ri)
f : Initiator efficiency.
kd : Decomposition rate constant.
[I] : molar concentration of initiator.
[M ·] : molar concentration of radical.
Слайд 25 c. Termination rate ( Rt )
d. Propagation rate
( Rp )
Steady state assumption.
Steady state assumption.
kt = ktc+ ktd
Ri=Rt
B. Kinetic of free radical polymerization.
Слайд 27 f. Gel effect : Trommsdorff effect, Norris-smith effect.
1) Difficult
termination reaction because of viscosity.
2) Ease propagation reaction because monomer size is small,
even though high viscosity.
3) Autoacceleration by exotherm of propagation reaction.
4) To obtain extraordinary high molecular weight polymer like gel.
2) Ease propagation reaction because monomer size is small,
even though high viscosity.
3) Autoacceleration by exotherm of propagation reaction.
4) To obtain extraordinary high molecular weight polymer like gel.
B. Kinetic of free radical polymerization.
Слайд 28 by hydrogen abstracting.
Lowering average kinetic chain length.
a. Growing radicals
move to other polymer chain.
b. Backbiting self polymer chain.
LDPE : branching polymer.
(6.33)
C. Chain transfer reactions : Growing radicals move to other parts
Слайд 29 c. Moving to initiators or monomers.
d. Moving to solvent.
(6.34)
(6.35)
(6.36)
(6.37)
C.
Chain transfer reactions
Слайд 30e. Moving to chain transfer agent.
Ct : Chain transfer constant.
[T] : Concentration of chain transfer agent.
f. Telomerization : At high concentration of transfer agent, ktr>kp.
Low-molecular-weight polymers are obtained.
(Telomer)
[T] : Concentration of chain transfer agent.
f. Telomerization : At high concentration of transfer agent, ktr>kp.
Low-molecular-weight polymers are obtained.
(Telomer)
(6.39)
C. Chain transfer reactions
Слайд 31
a. Copper(I) bypyridyl(bpy) complex:
b. TEMPO (18) : 2,2,6,6-tetramethylpiperidinyl-1-oxy.
(6.42)
(6.43)
(6.44)
(6.45)
D.
Leaving free radical polymerization : Atom transfer polymerization.
Слайд 32 c. Synthesis of block copolymers like anionic polymerization.
d. Monodisperse polymerization
(PI=1.05).
E. Kinetics of Emulsion polymerization.
a.
N : the number of particles.
b.
E. Kinetics of Emulsion polymerization.
a.
N : the number of particles.
b.
6.4 Kinetic and Mechanism of polymerization.
Слайд 336.5 Stereochemistry of polymerization.
A. General consideration.
a.
Stereoregular polymerization : Ionic and complex coordination
polymerization.
1) Terminal ion pair : counter ion.
2) Terminal complex active site.
3) Low temperature.
b. Stereo-irregular polymerization : Free-radical polymerization.
1) No stereoregulating radical terminal group.
2) Somewhat higher temperature.
polymerization.
1) Terminal ion pair : counter ion.
2) Terminal complex active site.
3) Low temperature.
b. Stereo-irregular polymerization : Free-radical polymerization.
1) No stereoregulating radical terminal group.
2) Somewhat higher temperature.
Слайд 34B. Factors influencing stereochemistry in free-radical polymerization.
a. Interaction between the
terminal chain carbon and the
approaching monomer molecule.
approaching monomer molecule.
C. Stereoregular free-radical polymerization of PMMA.
(syndiotatic PMMA)
a. Polymerization temperature : below 0℃.
b.
(6.48)
6.5 Stereochemistry of polymerization.
Слайд 35 c. Terminal carbon : sp2( planar )
Penultimate repeating unit :
Bulky ester group.
d. Poly(2,4,6-triphenylbenzylmethacrylate)
d. Poly(2,4,6-triphenylbenzylmethacrylate)
1) Less syndiotatic than PMMA.
2) More polar effect than steric effect.
6.5 Stereochemistry of polymerization.
19
Слайд 37A. Structure of conjugated Diene monoer.
Isoprene
B. a. 1,2-Addition :
Pendent vinyl group.
b. Stereochemistry : isotactic, syndiotactic, atactic.
6.6.2 Conjugated Dienes.
23
25
Слайд 38C. 1,4-Addition : Delocalized double bond
a.
D. 3,4-Addition
E.
Polymerization reaction and temperature.
24
26
27
29
6.6.2 Conjugated Dienes.
Слайд 39TABLE 6.6 Structure of Free Radical-Initiated Diene Polymersa
polymerization
Temperature (oC)
-20
20
100
233
-20
-5
50
100
257
-46
46
100
100
257
-46
46
100
Monomer
Butadiene
Isoprene
Chloroprene
cis-1,4 trans-1,4 1,2 3,4
Percent
6
22
28
43
1
7
18
23
12
5
10
13
77
58
51
39
90
82
72
66
77
94
81-86
71
17
20
21
18
5
5
5
5
2
1
2
2.4
-
-
-
-
4
5
5
6
9
0.3
1
2.4
aData from Cooper34 p. 275.
6.6.2 Conjugated Dienes.
Слайд 41
A. Thermodynamic feasibility.
a. ΔGp = ΔHp - TΔSp
ΔGp : Gibbs free energy change of polymerization.
ΔHp : Enthalpy change of polymerization.
ΔSp : Entropy change of polymerization.
ΔGp < 0 : favorable free energy of polymerization.
b. Values of ΔH and ΔS for several monomers.
c. Polypropylene and isobutylene :
ΔG < 0 → unfavorable polymerization.
because of kinetic feasibility
6.7 Monomer Reactivity
Слайд 43B. Factors of monomer reactivity in free radical polymerization.
a.
The stability of the monomer toward addition of a free radical.
b. The stability of the monomer radicals.
b. The stability of the monomer radicals.
c. Order of monomer reactivity.
Acrylonitrile > Styrene > Vinyl acetate.
d. Order of benzoyloxy radical initiation.
Syrene > Vinyl acetate > Acrylonitrile
Benzoyloxy radical : Ph14CO2․
6.7 Monomer Reactivity
Слайд 44C. The inverse relationship between monomer stability and
polymerization rate.
a.
Vinyl acetate: not Stable monomer but high rate constant.
b. Steric and polar effects: Not clear-cut generalization.
Lower rate constant of MMA than MA.
c. 1,2 disubstituted monomer difficult to polymerize in free radical.
Exception: Tetrafluoroethylene.
b. Steric and polar effects: Not clear-cut generalization.
Lower rate constant of MMA than MA.
c. 1,2 disubstituted monomer difficult to polymerize in free radical.
Exception: Tetrafluoroethylene.
6.7 Monomer Reactivity
Слайд 45D. Ceiling temperature (Tc)
a.
b. Definition of
ceiling temperature.
ΔGp = 0 : equal forward and backword reactions.
ΔGp = 0 : equal forward and backword reactions.
c. High Tc : favorable polymerization.
Low Tc : unfavorable polymerization.
Exception : α-methylstyrene (Tc=66℃).
6.7 Monomer Reactivity
Слайд 47 a.
b.
c. let,
(reactivity ratio)
steady state assumption.
d. solving
: Copolymer equation or copolymer composition equation.
d[M1]/d[M2] : the molar ratio of the two monomers in the copolymer
[M1], [M2] : the initial molar concentration of monomers in the
reaction mixture
steady state assumption.
d. solving
: Copolymer equation or copolymer composition equation.
d[M1]/d[M2] : the molar ratio of the two monomers in the copolymer
[M1], [M2] : the initial molar concentration of monomers in the
reaction mixture
B. Kinetics of copolymerization.
and
Слайд 48
a. r1 = r2 = ∞ : Homopolymer.
b. r1 = r2 = 0 : Alternating polymer.
c. r1 = r2 = 1 : Copolymer composition depending on feeding
monomers in the reaction temperature.
d. r1 × r2 = 1 :Ideal copolymerization like ideal liquid vaporization.
e. r1 × r2 > 1 : Azotropic copolymerization
(polymer composition not depending on feeding).
f. Determination of r1, r2 : Measure copolymer composition by
NMR or other method at low conversion ( <10% )
C. Significance of reactivity ratio (r1, r2).
Слайд 50E. Charge transfer complex polymerization(alternating copolymer).
a. Styrene
and maleic anhydride(D-A complex).
