Radical Polymerisation

1
Radical Polymerisation Chain or Addition
Polymerisation

• Carried out under undemanding conditions
• Simple
• Basic mechanism from the 1940s and 50s
• Well established
• Range of processes including Aqueous media

2
(No Transcript)
3
(No Transcript)
4
(No Transcript)
5
HEATS OF POLYMERISATION
MONOMER Hp (kcal mol-1) Ethylene 22.7 Prop
ylene 20.5 Isobutene 12.3 1,3
Butadiene 17.4 Isoprene 17.8 Styrene 1
6.7 -Methyl styrene 8.4 Vinyl
chloride 22.9 Vinylidene chloride 18.0 Tetr
afluoroethylene 37.2 Methyl acrylate 18.8 Me
thyl methacrylate 13.5 Vinyl
acetate 21.0 Hp refers to the conversion
of liquid monomer to amorphous or slightly
crystalline polymer
6
(No Transcript)
7
BULK (MASS) POLYMERISATION
Polymer
Monomer Initiator
FEATURES High purity ve very high
molecular weight (105 - 106) -ve
Exothermic - Trommsdorf Polymer/monomer
solubility
8
SUSPENSION (MINI BULK)
Monomer(s) Initiator (monomer soluble) Water Prote
ctive colloid
Water
--gt 200
Monomer Initiator
Protective Colloid

• Features
• Monomer droplets suspended in water stabilised
  by protective colloid
• Initiator soluble in water (cf Azo)
• Kinetics like bulk polymerisation BUT
• Taken to full conversion because viscosity
  independent of mol.wt conv

9
EMULSION POLYMERISATION
Monomer(s) - Water insoluble Initiator(s) -
Water soluble Surfactant(s) Water
INITIAL FINAL
Polymerisation
Monomer Droplets ps 1-10 um
Polymer Particles 0.05 -
0.3 um Volume fraction 0.5
10
monomer droplets (1-10 um)
m
I R1 R1. mn pptes
mn.

• Initiation in aqueous phase
• Oligomerisation in aqueous phase and
  precipitation onto existing particles or
  solubilisation in micelles
• Propagation in particles

11
(No Transcript)
12
(No Transcript)
13
INITIATION
Thermal Initiation
Peroxides e.g. Benzoyl Peroxide
Azo compounds e.g. AIBN
14
t 1/2 0.693/kd
15
Initiator efficiency

• Reaction with oxygen, solvent, impurity, etc
• Primary-primary radical combination
• Decomposition

f Rate of initiation of propagating chains
n. Rate of initiator disappearance
Effective Rate of Initiation Ri 2kd f I2
16
Photochemical decomposition

• Azo compounds 350 - 370 nm
• Used in PLP experiments to determine kp
• Also Diacyl Peroxides weak absorbance at 280 nm

17
Other types of Thermal Initiator
Cumyl Peroxide
t-Butyl peroxide
Hydroperoxides
Peresters
18
Redox Initiation
Usually carried out in aqueous systems e.g.
emulsion polymerisation
also Cr(II), V(II), Ti(III), Co(II), Cu(I)
Also Hydrogen Peroxide Fe(II), Ce(IV)
Organic, etc
19
Thermal self-initiation of Styrene
0.1 per hour at 60oC 2 _at_ 100oC
20
Chain Transfer
The chain transfer constant, C, is defined as the
ratio of the chain transfer and propagation rate
constants C ktr/kp Cs is the transfer
constant to transfer agent but also monomer,
solvent, polymer. The higher the value of C the
smaller amount is required to lower the MWt
21
(No Transcript)
22
CHAIN TRANSFER AGENTS
Chain transfer activity dependent upon the
monomer being polymerised and the structure of
the CTA eg Styrene _at_ 60oC CTA Cs x
104 Comment Benzene 0.02 Addition to
propagating Toluene 0.1 radical Ethyl
Benzene 0.7 Weakening of C-H Acetone
4.1 Bond Carbon 110 Weak C-C1
Bond Tetrachloride n-Butyl mercaptan 210,000 Wea
k S-H Bond
23
(No Transcript)
24
(No Transcript)
25
Generic Mayo plot
26
EFFECT OF CTA ON DEGREE OF POLYMERISATION FOR
STYRENE _at_ 60OC
n-Butyl mercaptan (CS 210,000)
CCl4 (CS 110)
1/DP 1/(mol.wt)
BENZENE (CS 0.02)
no CTA
Transfer Agent Styrene
27
EFFECT OF CTAS
Without eg mercaptans
Consumption then unmediated
Conversion
Hindered Phenols
Time
28
Macromolecules, 32 (19), 6019 -6030, 1999
Comparison of the Mayo and Chain Length
Distribution Procedures for the Measurement of
Chain Transfer Constants
DPn Mn/100.12
DPn Mw/(2 100.12)
29
Molecular weight distributions obtained in the
experiment for the determination of the chain
transfer constant of n-dodecanethiol in methyl
methacrylate at 40 C.
30
A typical molecular weight distribution plotted
as (a) w(log(M)) vs log(M) and (b) ln(P(M)) vs M.
The positions of the most important molecular
weight averages and the position where high is
determined (A-B) are indicated.
31
In summary, it can be concluded that both the
Mayo and CLD procedures are suitable and robust
for the determination of CS values under our
experimental conditions. In particular, neither
method is significantly affected by changing
initiator concentration i.e., any possible
chain-length dependence of the termination
reaction is not significantly affecting the
results of either method.
32
Catalytic Chain Transfer Polymerisation

• Use of low spin cobalt(II) macrocycles
• Typically MMACo 106 - 107

33
Polymerisation of MMA at 60 C with COBF
34
Catalytic Chain Transfer
35
Types of Catalysts
36
Mechanism of CCTP
37
(No Transcript)
38
(No Transcript)
39
Molecular weight distributions obtained in
supercritical CO2 (solid line) and the control
experiments run contemporaneously in bulk MMA
(dotted line)
40
Catalytic Chain Transfer Agents
41
Comparison of Catalysts
42
Emulsion Polymerisation
43
Emulsion Polymerisation of MMA by CCTP
K. G. Suddaby, D. M. Haddleton, Macromolecules,
1996, 29, 8083
44
Emulsion Polymerisation of MMA by CCTP
45
Macromolecules, 32 (12), 3907 -3912, 1999
Temperature dependence of the chain transfer
constants of COBF in the free-radical
polymerizations of () MMA, () EMA and () BMA in
the temperature range of 40-70 C
46
MALDI TOF MS of a BMA-MMA Co-Polymer by Emulsion
CCT
47
Acrylate Monomers
No Catalytic Chain Transfer Cobalt-Mediated
Living Polymerisation
B. B. Wayland, L. Basickles, S. Murkerjee, M. Wei
and M. Fryd, Macromolecules, 1997, 30, 8109
48
CCT with different Monomers
CS 30,000 ktr 1.4?107
CS 600 ktr 1?105
CS 800,000 ktr 1?106
see T. P. Davis and H Heuts, Macromolecules. 1999
49
CCTP methacrylic acid by aq. CCTP
App CS 1500
50
Further reaction of CCTP macromonomer products
51
Macromonomer Synthesis via Addition-Fragmentation
The Use of a-Bromomethylated Monomers
allyl bromide (XC, YC, zH and RBr) methyl
a-bromo methacrylate (XC, YC, zCO2Me and RBr)
52
Controlled/Living Radical Polymerisation
Atom Transfer Polymerisation Cu(I)Br/Ligand RAF
T thioesters/xanthates Nitroxide
mediated stable free radicals e.g. TEMPO
53
(No Transcript)
54
Control of Macro-Molecular Structure
Molecular weight Chain Architecture
Functionality Rate/Exotherm
55
Commercial impact of living/controlled
polymerisation

• Anionic Polymerisation is the most
• established form of living polymerisation
• Although discovered in 1956 commercial
  applications have probably not lived up to
  expectations
• Notable exception is styrene-diene
• block/star copolymers (Kraton rubbers)
• Generally anionic polymerisation requires low
• temperatures, solvents which do not chain
  transfer and extremely pure solvents and
  reagents.

56
RAFT Polymerisation
57
Macromolecules, ASAP Article 10.1021/ma991451a
S0024-9297(99)01451-5 Web Release Date January
6, 2000
58
GPC traces of (a) PMA prepared using 5 and (b)
the same PMA treated with ethylenediamine in THF
at room temperature
59
GPC traces for (a) PSt 9 (n 20 100, w/n
1.11), prepared in bulk at 110 C
using S,S-di(1-phenylethyl)trithiocarbonate 6
(0.0173 M) as the chain transfer agent and (b)
poly(styrene-block-n-butyl acrylate-block-styrene)
(n 161 500, w/n 1.16) prepared by chain
extension of PSt 9 (0.0016 M) with n-butyl
acrylate (2.79 M), AIBN (0.073 10-2M) at 60 C
for 8 h.
60
Macromolecules, 31 (16), 5559 -5562, 1998
Living Free-Radical Polymerization by
Reversible Addition-Fragmentation Chain Transfer
The RAFT Process
61
Molecular weight distributions for
poly(styrene-co-acrylonitrile) polymerized
by heating styrene and acrylonitrile (6238 mole
ratio) at 100 C in the presence of cumyl
dithiobenzoate
62
Reversible Homolytic Dissociation

• Covalent adduct
• Persistent radical

63
Acc. Chem. Res., 30 (9), 373 -382, 1997
64
Variation in experimentally determined molecular
weight, Mn, and the theoretical molecular
weights for thepolymerization of styrene at 125 C
using varying amounts of the unimolecular
initiator 9.
65
CRP of Styrene in Bulk

• T 393 K
• L0 5 10-2 M

66
Library of alkoxyamine structures evaluated as
initiators for the living free radical
polymerization of styrene and n-butyl acrylate.
67
TEMPO
68
Living Polymerisation of Dienes
69
(No Transcript)
70
Macromolecules, 31 (2), 213 -219, 1998
71
(No Transcript)
72
(No Transcript)
73
K. Matyjaszewski Macromolecules 1997, 30, p7697
7042 7034 7348 8161 7692 6507, 6513, 6398
JACS 1997, 119, p674 V Percec Macromolecules
1997, 30, p6705, 8526 M Sawamoto Macromolecules
1997, 30, p2244, 2249 Teyssie Macromolecules
1997, 30, p7631, Haddleton Macromolecules 1997,
30, p2190
74
Macromolecules, 30 (25), 7697 -7700, 1997.
75
Macromolecules, 31 (4), 1064 -1069, 1998
76
(No Transcript)
77
Macromolecules, 31 (20), 6762 -6768, 1998
Jiro Ueda, Masami Kamigaito, and Mitsuo Sawamoto
78
Macromolecules, 31 (20), 6756 -6761, 1998
Hiroko Uegaki, Yuzo Kotani, Masami Kamigaito,
and Mitsuo Sawamoto
79
Macromolecules, 32 (7), 2204 -2209, 1999
80
(No Transcript)
81
Reaction rate dependence on the Cu(I)
82
Too much catalyst leads to problems of cost
and residual metal in products. Rate can be
accelerated Reduction of copper(II) to
copper(I) e.g. disproportionation with
copper(0) - Matyjaszewski Addition of rate
enhancers e.g. acid, alcohols Use of mildly
co-ordinated solvents However, for many
applications we require Much lower levels of
metal Recycling of metal Acceptable rates of
polymerisation
83
(No Transcript)
84
Synthesis of Initiators from alcohols
85
?- Functional polymers from functional initiators
based on phenols
86
Synthesis of Oligosaccharide-Carrying Initiator
Ac2O, DMAP
H2SO4
in Pyridine, at r.t.
in Ac2O, at 55 oC
Benzylamine
in THF, at r.t.
Triethylamine
in CH2Cl2, at 0 oC
87
Macromolecules, 31 (2), 538 -541, 1998
88
Macromolecules, 31 (20), 6748 -6755, 1998
89
(No Transcript)