Topics in Current Chemistry (2018) 376:44
1 3
in THF/hexane (99/1 v/v) used as the initiator. The polymers/copolymers could be
obtained at the temperature from − 28 °C to room temperature with narrow molecular weight distributions (PDI < 2) by virtue of fast mixing and precise residence time
control in the microreactor. Moreover, block polymerization could be achieved with
sequential use of two different monomers in this microreactor system. As claimed
by the authors, the observations illustrated in this work open a new possibility of
living anionic polymerization for the synthesis of structurally well-defined polymers
and copolymers having various functions in both laboratory synthesis and industrial
production.
Nagaki et al. conducted the living anionic polymerization of styrene in THF/
hexane in the microreactor system, which was integrated by two T-micromixers and
two microchannel reactors [114]. n-BuLi or s-BuLi could be used as an initiator in
this polymerization process. Poly(styrene) with high molecular weight ranging from
5000 to 14,000 and accordingly with the PDI values of 1.06–1.17 could be synthesized. Moreover, the microreactor system could continuously run for 3 h producing
1 kg of the polymer. Although the production still had large room to be increased,
this study exhibited the potential application of microreactors in the scale-up for living anionic polymerization.
4.3.1 Controlled Radical Polymerization
Free radical polymerization (FRP) processes can meet more than half of the polymer
production in industry. However, it is difficult to control the macromolecular structure and the molecular weight distribution precisely via FRP due to the uncontrollable reaction mechanism. Nevertheless, the application of living polymerization also
has intrinsic limitations due to its stringent reaction conditions and rather confined
adaptable monomers. Controlled radical polymerization (CRP), combining the characteristics of FRP and living polymerization, has been developed and attracted much
attention since the 1980s. Active and dormant species can be balanced during CRP.
CRP is based on an equilibrium between the active and dormant species, which slows
the rate of propagation and enables uniform chain growth while limiting the termination of the reaction, thus inherently improving the controllability of macromolecular features. A variety of monomers can be polymerized to form macromoleculars
with well-defined structures and narrow molecular weight distributions by the CRP
method including atom transfer radical polymerization (ATRP), reversible additionfragmentation chain transfer radical polymerization (RAFT), and nitroxide-mediated
polymerization (NMP) [110, 115]. In the past several years, CRP has been conducted
by the continuous-flow approach with the development of microreactor technology.
4.4 ATRP Processes
Parida et al. carried out the polymerization of 2-(dimethylamino) ethyl methacrylate
using the ATRP method in tubular microreactors with inner diameters from 0.876 to
4.083 mm [116]. The polymers with the molecular weight of about 2 × 10
4
g/mol and
the PDI value below 1.7 were synthesized with the throughput from 0.28 to 5.66 g/h.
166
Reprinted from the journal
1 3
in THF/hexane (99/1 v/v) used as the initiator. The polymers/copolymers could be
obtained at the temperature from − 28 °C to room temperature with narrow molecular weight distributions (PDI < 2) by virtue of fast mixing and precise residence time
control in the microreactor. Moreover, block polymerization could be achieved with
sequential use of two different monomers in this microreactor system. As claimed
by the authors, the observations illustrated in this work open a new possibility of
living anionic polymerization for the synthesis of structurally well-defined polymers
and copolymers having various functions in both laboratory synthesis and industrial
production.
Nagaki et al. conducted the living anionic polymerization of styrene in THF/
hexane in the microreactor system, which was integrated by two T-micromixers and
two microchannel reactors [114]. n-BuLi or s-BuLi could be used as an initiator in
this polymerization process. Poly(styrene) with high molecular weight ranging from
5000 to 14,000 and accordingly with the PDI values of 1.06–1.17 could be synthesized. Moreover, the microreactor system could continuously run for 3 h producing
1 kg of the polymer. Although the production still had large room to be increased,
this study exhibited the potential application of microreactors in the scale-up for living anionic polymerization.
4.3.1 Controlled Radical Polymerization
Free radical polymerization (FRP) processes can meet more than half of the polymer
production in industry. However, it is difficult to control the macromolecular structure and the molecular weight distribution precisely via FRP due to the uncontrollable reaction mechanism. Nevertheless, the application of living polymerization also
has intrinsic limitations due to its stringent reaction conditions and rather confined
adaptable monomers. Controlled radical polymerization (CRP), combining the characteristics of FRP and living polymerization, has been developed and attracted much
attention since the 1980s. Active and dormant species can be balanced during CRP.
CRP is based on an equilibrium between the active and dormant species, which slows
the rate of propagation and enables uniform chain growth while limiting the termination of the reaction, thus inherently improving the controllability of macromolecular features. A variety of monomers can be polymerized to form macromoleculars
with well-defined structures and narrow molecular weight distributions by the CRP
method including atom transfer radical polymerization (ATRP), reversible additionfragmentation chain transfer radical polymerization (RAFT), and nitroxide-mediated
polymerization (NMP) [110, 115]. In the past several years, CRP has been conducted
by the continuous-flow approach with the development of microreactor technology.
4.4 ATRP Processes
Parida et al. carried out the polymerization of 2-(dimethylamino) ethyl methacrylate
using the ATRP method in tubular microreactors with inner diameters from 0.876 to
4.083 mm [116]. The polymers with the molecular weight of about 2 × 10
4
g/mol and
the PDI value below 1.7 were synthesized with the throughput from 0.28 to 5.66 g/h.
166
Reprinted from the journal