NMP Using Flow Microreactor Systems
NMP [191–193] can be applied to a wide range of monomers such as styrenes,
acrylates, acrylamides, acrylonitrile, and 1,3-dienes. Acyclic nitroxides such as
2,2,5-trimethyl-4-phenyl-3-azahexane-3-nitroxide (TIPNO) or N-tert-butyl-N-(1diethyl phosphono-2,2-dimethylpropyl) nitroxide (DEPN) enables the reversible
termination of the growing polymer chains.
NMP of styrene and n-butyl acrylate at 140
C has been performed in a
continuous-flow microtubular reactor (Fig. 27) consisting of a stainless steel tube
reactor and a back-pressure cartridge [212]. In the case of styrene polymerization,
there is no difference between batch reactors and flow microreactors. However, for
n-butyl acrylate, a better control of the polymerization has been observed in the
flow microreactor (M w /M n of 1.80 for the batch reactor and 1.44 for the flow
microreactor). Moreover, consumption of the monomer is much faster using the
flow microreactor (Fig. 28).
NMP of styrene in a miniemulsion can be also performed in a tubular reactor
[213]. In the first step, a macroinitiator is prepared by bulk polymerization in a batch
reactor and the subsequent miniemulsion polymerization is carried out in a tubular
reactor. The polymerization kinetics in the tubular reactor are similar to those in
a batch reactor. It is also noteworthy that both preparation of a macroinitiator and
a miniemulsion polymerization can be achieved in a continuous tubular reactor to
obtain polystyrene-block-poly(butyl acrylate) diblock and polystyrene-block-poly
(butyl acrylate)-block-polystyrene triblock copolymers [214].
Fig. 27 Continuous flow microreactor system for nitroxide-mediated radical polymerization
(NMP) of poly(styrene) or poly(n-butyl acrylate). R microtube reactor
Table 6 Conversion of the RAFT polymerization and poly(nisopropylacrylamide) (PNIPAM)
properties after 60 min at 90
C
Method
Heating method
Conversion (%)
M n
M w /M n
Flow
Oil bath
88
21,500
1.15
Flow
Oil bath
78
17,200
1.31
Flow
Oil bath
79
20,000
1.31
Batch
Oil bath
40
13,400
1.12
Batch
Microwave
85
19,400
1.16
26
A. Nagaki and J.-i. Yoshida
NMP [191–193] can be applied to a wide range of monomers such as styrenes,
acrylates, acrylamides, acrylonitrile, and 1,3-dienes. Acyclic nitroxides such as
2,2,5-trimethyl-4-phenyl-3-azahexane-3-nitroxide (TIPNO) or N-tert-butyl-N-(1diethyl phosphono-2,2-dimethylpropyl) nitroxide (DEPN) enables the reversible
termination of the growing polymer chains.
NMP of styrene and n-butyl acrylate at 140
C has been performed in a
continuous-flow microtubular reactor (Fig. 27) consisting of a stainless steel tube
reactor and a back-pressure cartridge [212]. In the case of styrene polymerization,
there is no difference between batch reactors and flow microreactors. However, for
n-butyl acrylate, a better control of the polymerization has been observed in the
flow microreactor (M w /M n of 1.80 for the batch reactor and 1.44 for the flow
microreactor). Moreover, consumption of the monomer is much faster using the
flow microreactor (Fig. 28).
NMP of styrene in a miniemulsion can be also performed in a tubular reactor
[213]. In the first step, a macroinitiator is prepared by bulk polymerization in a batch
reactor and the subsequent miniemulsion polymerization is carried out in a tubular
reactor. The polymerization kinetics in the tubular reactor are similar to those in
a batch reactor. It is also noteworthy that both preparation of a macroinitiator and
a miniemulsion polymerization can be achieved in a continuous tubular reactor to
obtain polystyrene-block-poly(butyl acrylate) diblock and polystyrene-block-poly
(butyl acrylate)-block-polystyrene triblock copolymers [214].
Fig. 27 Continuous flow microreactor system for nitroxide-mediated radical polymerization
(NMP) of poly(styrene) or poly(n-butyl acrylate). R microtube reactor
Table 6 Conversion of the RAFT polymerization and poly(nisopropylacrylamide) (PNIPAM)
properties after 60 min at 90
C
Method
Heating method
Conversion (%)
M n
M w /M n
Flow
Oil bath
88
21,500
1.15
Flow
Oil bath
78
17,200
1.31
Flow
Oil bath
79
20,000
1.31
Batch
Oil bath
40
13,400
1.12
Batch
Microwave
85
19,400
1.16
26
A. Nagaki and J.-i. Yoshida