1.3 Anionic Polymerization
1.3.1 Controlled/Living Anionic Polymerization of Vinyl Monomers
Living anionic polymerizations have received significant attention since Michael
Szwarc’s first report in 1956 [132]. Anionic polymerization [133–137] serves as an
important and powerful method for macromolecular engineering, permitting the
preparation of highly defined block copolymers, star polymers, and further complex
architectures, because the anionic polymer ends are living even in the absence of a
capping agent [138, 139]. In fact, the anionic growing polymer ends (usually
organolithium species) can be utilized for end-functionalization reactions with
various electrophiles and block copolymerization with other monomers. A major
drawback of conventional anionic polymerization in polar solvents in batch
macroreactors is the requirement for low temperatures, such as À78
C [140]. Such
a requirement causes severe limitations in the use of this highly useful polymerization
in industry. Using nonpolar solvents, the polymerization can be conducted at higher
temperatures, but much longer reaction time is needed for completion. It is also
problematic that the use of individually manufactured laboratory equipment is
frequently necessary.
Kinetic studies on anionic polymerization in a continuous flow mode have
also been reported by Szwarc and coworkers [141, 142], Schulz and coworkers
[141, 142], and Muller and coworkers [143, 144]. However, preparative anionic
polymerizations in continuous flow mode have not been studied until recently.
1.3.2 Controlled/Living Anionic Polymerization of Styrenes
Anionic polymerization of styrenes is a highly useful technique for the synthesis
of polystyrenes with precisely adjustable molecular weights and molecular weight
distributions and is applied for the synthesis of structurally well-defined polymers
such as end-functionalized polymers and block copolymers.
Controlled/Living Anionic Polymerization of Styrenes in Polar Solvent Using Flow
Microreactor Systems [145]
In a conventional anionic polymerization of styrenes in polar solvents in a batch
macroreactor, major drawbacks include the requirement of low temperature such
as À78
C. In contrast, Nagaki et al. reported that controlled anionic polymerization
of styrene can be conducted under easily accessible conditions such as 0
C in a
polar solvent using a flow microreactor to obtain the polystyrene with narrower
molecular weight distribution (M n ¼ 1,200–20,000, M w /M n ¼ 1.09–1.13) (Fig. 9)
[146]. Moreover, the molecular weight can be easily controlled by changing the
flow rates of monomer and initiator solutions. Furthermore, these methods can be
Controlled Polymerization in Flow Microreactor Systems
13
1.3.1 Controlled/Living Anionic Polymerization of Vinyl Monomers
Living anionic polymerizations have received significant attention since Michael
Szwarc’s first report in 1956 [132]. Anionic polymerization [133–137] serves as an
important and powerful method for macromolecular engineering, permitting the
preparation of highly defined block copolymers, star polymers, and further complex
architectures, because the anionic polymer ends are living even in the absence of a
capping agent [138, 139]. In fact, the anionic growing polymer ends (usually
organolithium species) can be utilized for end-functionalization reactions with
various electrophiles and block copolymerization with other monomers. A major
drawback of conventional anionic polymerization in polar solvents in batch
macroreactors is the requirement for low temperatures, such as À78
C [140]. Such
a requirement causes severe limitations in the use of this highly useful polymerization
in industry. Using nonpolar solvents, the polymerization can be conducted at higher
temperatures, but much longer reaction time is needed for completion. It is also
problematic that the use of individually manufactured laboratory equipment is
frequently necessary.
Kinetic studies on anionic polymerization in a continuous flow mode have
also been reported by Szwarc and coworkers [141, 142], Schulz and coworkers
[141, 142], and Muller and coworkers [143, 144]. However, preparative anionic
polymerizations in continuous flow mode have not been studied until recently.
1.3.2 Controlled/Living Anionic Polymerization of Styrenes
Anionic polymerization of styrenes is a highly useful technique for the synthesis
of polystyrenes with precisely adjustable molecular weights and molecular weight
distributions and is applied for the synthesis of structurally well-defined polymers
such as end-functionalized polymers and block copolymers.
Controlled/Living Anionic Polymerization of Styrenes in Polar Solvent Using Flow
Microreactor Systems [145]
In a conventional anionic polymerization of styrenes in polar solvents in a batch
macroreactor, major drawbacks include the requirement of low temperature such
as À78
C. In contrast, Nagaki et al. reported that controlled anionic polymerization
of styrene can be conducted under easily accessible conditions such as 0
C in a
polar solvent using a flow microreactor to obtain the polystyrene with narrower
molecular weight distribution (M n ¼ 1,200–20,000, M w /M n ¼ 1.09–1.13) (Fig. 9)
[146]. Moreover, the molecular weight can be easily controlled by changing the
flow rates of monomer and initiator solutions. Furthermore, these methods can be
Controlled Polymerization in Flow Microreactor Systems
13