活性自由基聚合,RAFT
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2. The intermediate radicals 2 and 4 should fragment rapidly
(high kβ, weak S–R bond) and give no side reactions. 3. The intermediate 2 should partition in favour of products (kβ ≥k–add).
The proportion of dead chains Dc：
Ctr = ktr / k p
忽略引发和双基 终止产生的链
Ctr 测定：
传统自由基聚合测链转移常数：
11
[T ]
Xn
X n0
CT
[M ]
Ctr 测定： 不忽略引发和双基终止产生的链
C−tr = 0, and for less active RAFT agents at low monomer conversion
4. The expelled radicals (R•) must efficiently re-initiate the
polymer molecular weight distributions for a conventional and a RAFT polymerization of styrene under similar experimental conditions.
Xn(calc) is the expected number-average degree of
polymerization assuming complete consumption of transfer agent.
Ctr 的主要影响因素: R和Z基团
Z基团可以活化C=S键，使其更容易与自由基发生反应，而R 基团一般是一个良好的均裂离去基团，并且离去后产生的自由 基R应可以有效地再引发单体的聚合。改变Z与R基团结构， 相应的Ctr大小可以有5个数量级的改变(0.01到1000以上)。
Macromolecules 1998, 31, 5559-5562
RAFT聚合机理和动力学：
稳态与平衡，与ITP相同：
A steady state concentration of radicals is established via initiation and termination processes as in conventional RP.
The deactivation-activation equilibria are chain-transfer reactions.
Radical–radical termination is not directly
suppressed by the RAFT process.
稳态与平衡：
RAFT Polymerization Schematic
CM
CI
[I] [M ]
CS
[S] [M ]
CP
[P] [M ]
1 Xn
(C 2
D)
2kt Rp k p2[M ]2
CM
CI
[I] [M ]
CS
[S] [M ]
CP
[P] [M ]
1 Xn
CA
[ A] [M ]
调聚反应！
基于可逆加成-碎裂型链转移剂的 活性自由基聚合
CSIRO，澳大利亚联邦科学与工业研究组织( Commonwealth Scientific and Industrial Research Organisation )
is the initiator efficiency.
原因：MMA歧化终止为主，St几乎都为偶合终止！
（7）The fraction of living chains (L)
M n,exp / M n,th （8）
In an ideal RAFT process，L=1.0
In a well-designed RAFT polymerization, L will be >0.95。
The transfer constants of various RAFT agents have been measured in the range of 0.01 to above 1000 depending on the nature of Z, R, and type of monomer. It has been reported that to obtain narrow polydispersity polymers (Mw=Mn < 1.5) in a batch process with degenerative chain transfer (e.g., RAFT process), the Ctr of the transfer agent should be greater than 2. However, this limitation can be overcome by the use of a monomer feed polymerization process to reduce the rate of propagation and thereby produce narrow polydispersity polymers from a less active CTA.
In an ideal RAFT process, the RAFT agent should behave as a transfer agent. Retention of the thiocarbonylthio groups in the polymeric product is responsible for the living character of RAFT polymerization and renders the process suitable for synthesizing block copolymers and end functional polymers.
烯丙基硫化物链转移剂的分子结构式
硫代羰基化合物类链转移剂的分子结构式
加成-断裂均为高活性，大分子的加成断裂也为高活性！ reversible addition-fragmentation chain transfer (RAFT) agent
Preequilibrium Main equilibrium
In 1986, CSIRO in Australia reported the use of PMMA macromonomers as chain transfer agents (CTAs) in radical polymerization. They called the process addition-fragmentation chain transfer (AFCT):
当链较长后φ为0.5
ktr
k
k add kadd k
k (1 )
忽略引发剂产生的链
（5）
d is the number of chains produced in a radical–radical termination event (d ∼ 1.67 for MMA polymerization and ∼1.0 for styrene polymerization) and f
Z基团的影响：
苯乙烯本体聚合(80℃)中的结果表明，相同R不同Z的RAFT 试剂链转移常数按下面的次序递减:二硫代苯甲酸酯>三硫代 碳酸酯~脂肪二硫代羧酸酯>黄原酸酯>二硫代氨基甲酸酯。 （最后两种基本不可控）
最后两种：Z基团给电子性，降低C=S的反应活性？
当富电子原子（O/N)上有吸电子取代基，特别是可与O/N原子中孤 对电子发生离域作用的取代基取代后，可以显著提高其转移常数。
Moad, G.; Rizzardo, E.; Thang, S. H. Acc. Chem. Res. 2008, 41, 1133-1142.
Preequilibrium mainequilibrium
Ctr = ktr / k p
Ctr= ktr / ki
ktr
kadd
k kadd k
kadd
In the early 1980s a CSIRO team led by David Solomon and Ezio Rizzardo devised a radical-trapping technique. During the next decade the team introduced catalytic chain transfer agents, macromonomers, additionfragmentation chemistry and pioneered a form of living radical polymerisation mediated by nitroxides. The patent for this last invention Nitroxide-mediated living radical polymerisation (NMP) has been in the top 10 of the world's most cited patents since 1999 (CAS Science Spotlight). The novelty and the potential industrial utility of their science was recognised by DuPont in 1990 and a Strategic Research Alliance with CSIRO formed.
1988-1996年间 irreversible addition-fragmentation chain transfer agent,
分子量调节剂，末端官能化试剂（引入双键等）
irreversible addition-fragmentation chain transfer agent, 分子量调节剂，末端官能化试剂
基于可逆加成-碎裂型链转移剂 的活性自由基聚合
Living radical polymerization in the presence of reversible addition-fragmentation chain transfer –RAFT, 1998
1 Xn
(C 2
D)
2kt Rp k p2[M ]2
A negative deviation from the line predicted by equation indicates that other sources of polymer chains are significant (e.g. the initiator, chain transfer to solvent, monomer). A positive deviation from the line predicted by equation indicates incomplete usage of transfer agent。
Initiator/RAFT 多为5/1, 更宽的范围为20:1-3:1
For an efficient RAFT polymerization:
1. The initial RAFT agents 1 and the polymer RAFT agent 3
should have a reactive C=S double bond (high kadd).
R基团的影响：
R基团对自由基与RAFT试剂的反应没有太大影响，但它决定 反应中形成的自由基中间体的分解方向，而分解形成的自由基 R·的立体位阻、极化性能和稳定性等决定了一个RAFT试剂链 转移常数的大小。R·的离去能力和再引发能力要平衡！
不同R基团有如下递减规律: -C(alkyl)2CN,-C(Me)2Ar> -C(Me)2(C=O)O(alkyl)> -C(Me)2(C=O)NH(alkyl)> -C(Me)2CH2C(Me)3≥ -C(Me)HPh> -C(Me)3, -CH2ph，只有当 R=C(Me)2Ph和-C(Me)2CN时才能得到可控的MMA聚合物。
(high kβ, weak S–R bond) and give no side reactions. 3. The intermediate 2 should partition in favour of products (kβ ≥k–add).
The proportion of dead chains Dc：
Ctr = ktr / k p
忽略引发和双基 终止产生的链
Ctr 测定：
传统自由基聚合测链转移常数：
11
[T ]
Xn
X n0
CT
[M ]
Ctr 测定： 不忽略引发和双基终止产生的链
C−tr = 0, and for less active RAFT agents at low monomer conversion
4. The expelled radicals (R•) must efficiently re-initiate the
polymer molecular weight distributions for a conventional and a RAFT polymerization of styrene under similar experimental conditions.
Xn(calc) is the expected number-average degree of
polymerization assuming complete consumption of transfer agent.
Ctr 的主要影响因素: R和Z基团
Z基团可以活化C=S键，使其更容易与自由基发生反应，而R 基团一般是一个良好的均裂离去基团，并且离去后产生的自由 基R应可以有效地再引发单体的聚合。改变Z与R基团结构， 相应的Ctr大小可以有5个数量级的改变(0.01到1000以上)。
Macromolecules 1998, 31, 5559-5562
RAFT聚合机理和动力学：
稳态与平衡，与ITP相同：
A steady state concentration of radicals is established via initiation and termination processes as in conventional RP.
The deactivation-activation equilibria are chain-transfer reactions.
Radical–radical termination is not directly
suppressed by the RAFT process.
稳态与平衡：
RAFT Polymerization Schematic
CM
CI
[I] [M ]
CS
[S] [M ]
CP
[P] [M ]
1 Xn
(C 2
D)
2kt Rp k p2[M ]2
CM
CI
[I] [M ]
CS
[S] [M ]
CP
[P] [M ]
1 Xn
CA
[ A] [M ]
调聚反应！
基于可逆加成-碎裂型链转移剂的 活性自由基聚合
CSIRO，澳大利亚联邦科学与工业研究组织( Commonwealth Scientific and Industrial Research Organisation )
is the initiator efficiency.
原因：MMA歧化终止为主，St几乎都为偶合终止！
（7）The fraction of living chains (L)
M n,exp / M n,th （8）
In an ideal RAFT process，L=1.0
In a well-designed RAFT polymerization, L will be >0.95。
The transfer constants of various RAFT agents have been measured in the range of 0.01 to above 1000 depending on the nature of Z, R, and type of monomer. It has been reported that to obtain narrow polydispersity polymers (Mw=Mn < 1.5) in a batch process with degenerative chain transfer (e.g., RAFT process), the Ctr of the transfer agent should be greater than 2. However, this limitation can be overcome by the use of a monomer feed polymerization process to reduce the rate of propagation and thereby produce narrow polydispersity polymers from a less active CTA.
In an ideal RAFT process, the RAFT agent should behave as a transfer agent. Retention of the thiocarbonylthio groups in the polymeric product is responsible for the living character of RAFT polymerization and renders the process suitable for synthesizing block copolymers and end functional polymers.
烯丙基硫化物链转移剂的分子结构式
硫代羰基化合物类链转移剂的分子结构式
加成-断裂均为高活性，大分子的加成断裂也为高活性！ reversible addition-fragmentation chain transfer (RAFT) agent
Preequilibrium Main equilibrium
In 1986, CSIRO in Australia reported the use of PMMA macromonomers as chain transfer agents (CTAs) in radical polymerization. They called the process addition-fragmentation chain transfer (AFCT):
当链较长后φ为0.5
ktr
k
k add kadd k
k (1 )
忽略引发剂产生的链
（5）
d is the number of chains produced in a radical–radical termination event (d ∼ 1.67 for MMA polymerization and ∼1.0 for styrene polymerization) and f
Z基团的影响：
苯乙烯本体聚合(80℃)中的结果表明，相同R不同Z的RAFT 试剂链转移常数按下面的次序递减:二硫代苯甲酸酯>三硫代 碳酸酯~脂肪二硫代羧酸酯>黄原酸酯>二硫代氨基甲酸酯。 （最后两种基本不可控）
最后两种：Z基团给电子性，降低C=S的反应活性？
当富电子原子（O/N)上有吸电子取代基，特别是可与O/N原子中孤 对电子发生离域作用的取代基取代后，可以显著提高其转移常数。
Moad, G.; Rizzardo, E.; Thang, S. H. Acc. Chem. Res. 2008, 41, 1133-1142.
Preequilibrium mainequilibrium
Ctr = ktr / k p
Ctr= ktr / ki
ktr
kadd
k kadd k
kadd
In the early 1980s a CSIRO team led by David Solomon and Ezio Rizzardo devised a radical-trapping technique. During the next decade the team introduced catalytic chain transfer agents, macromonomers, additionfragmentation chemistry and pioneered a form of living radical polymerisation mediated by nitroxides. The patent for this last invention Nitroxide-mediated living radical polymerisation (NMP) has been in the top 10 of the world's most cited patents since 1999 (CAS Science Spotlight). The novelty and the potential industrial utility of their science was recognised by DuPont in 1990 and a Strategic Research Alliance with CSIRO formed.
1988-1996年间 irreversible addition-fragmentation chain transfer agent,
分子量调节剂，末端官能化试剂（引入双键等）
irreversible addition-fragmentation chain transfer agent, 分子量调节剂，末端官能化试剂
基于可逆加成-碎裂型链转移剂 的活性自由基聚合
Living radical polymerization in the presence of reversible addition-fragmentation chain transfer –RAFT, 1998
1 Xn
(C 2
D)
2kt Rp k p2[M ]2
A negative deviation from the line predicted by equation indicates that other sources of polymer chains are significant (e.g. the initiator, chain transfer to solvent, monomer). A positive deviation from the line predicted by equation indicates incomplete usage of transfer agent。
Initiator/RAFT 多为5/1, 更宽的范围为20:1-3:1
For an efficient RAFT polymerization:
1. The initial RAFT agents 1 and the polymer RAFT agent 3
should have a reactive C=S double bond (high kadd).
R基团的影响：
R基团对自由基与RAFT试剂的反应没有太大影响，但它决定 反应中形成的自由基中间体的分解方向，而分解形成的自由基 R·的立体位阻、极化性能和稳定性等决定了一个RAFT试剂链 转移常数的大小。R·的离去能力和再引发能力要平衡！
不同R基团有如下递减规律: -C(alkyl)2CN,-C(Me)2Ar> -C(Me)2(C=O)O(alkyl)> -C(Me)2(C=O)NH(alkyl)> -C(Me)2CH2C(Me)3≥ -C(Me)HPh> -C(Me)3, -CH2ph，只有当 R=C(Me)2Ph和-C(Me)2CN时才能得到可控的MMA聚合物。