Topics in Current Chemistry (2018) 376:44
1 3
Kermagoret et al. conducted the cobalt-mediated free-radical photopolymerization of vinyl acetate (VAc) or vinyl acetate/1-octene (VAc/1-Oct) in
a microreactor with ultraviolet irradiation [170]. The alkyl cobalt(III) adduct
([Co(acac) 2 (CH(OAc)–CH 2 ) <4 R 0 ] was used as the initiator of this polymerization,
which generated the radicals in the presence of light. Their results demonstrated
that the microreactor technology not only benefited the preparation of highly pure
poly(vinyl acetate) but also significantly accelerated the polymerization process. In
the preparation of poly(vinyl acetate) by ultraviolet photopolymerization, the conventional batch reactor produced a large part of side products. Interestingly, when
the reaction was carried out in the microreactor, poly(vinyl acetate) was obtained
with a well-defined monomodal mode. This photomicroreactor system was further applied for the copolymerization of vinyl acetate with reactive olefins (e.g.,
1-octene) with the help of iniferter.
Johnson and Chen constructed simple, scalable, and efficient continuous-flow
microreactor systems for the photo-controlled living radical polymerization with the
use of trithiocarbonate (TTC) as an iniferter to produce telechelic poly(N-isopropylacrylamide) (pNiPAAm) and relevant block-polymers [171]. It was proven that
metal-free and switchable photopolymerization could be achieved under flow conditions. Compared to the photo-controlled living radical polymerization in the batch
reactor, the microreactor could accelerate the preparation of polymers with high
molecular weights (e.g., 109,400 g mol
−1
). Cycles of on/off photo-controlled living
radical polymerization in a continuous-flow microreactor confirmed that externally
stimulated light acted as a function of controlled living polymerization (see Fig. 13).
Notably, this photomicroreactor setup could be easily alternated for reactions with
different monomer/TTC ratios enabling control over the molecular weights and
molecular weight distributions. It was claimed that the operational simplicity of
such a continuous-flow technique and its ability to produce high-quality polymers
in a scalable fashion would make it a useful strategy for both academia and industry.
Recently, Melker et al. reported the synthesis of poly(methyl methacrylate)
through the controlled-radical polymerization of Ir-catalyzed photooxidation reduction in a microreactor [172]. In this process, ethyl α-bromophenyl acetate was used
as an initiator, which could induce the MMA polymerization under the visible
light illumination. In particular, different capillary microreactors constructed with
four widely used tube materials including PFA, FEP, tetrafluoroethylene (Tefzel),
and ethylene chlorotrifluoroethylene (Halar) were applied for this photo-mediated polymerization. It was found that the use of the Halar capillary microreactor
with low oxygen permeability was critical for the successful implementation of
this photopolymerization. A first-order kinetics was revealed in both conventional
batch reactors and microreactors, and the polymerization rate with the continuousflow processing was increased by at least 50% compared to conventional batch
polymerization.
Eckardt et al. reported the synthesis of branched poly(butyl acrylate)s using the
photo-induced free-radical polymerization of (n/t)-butyl acrylate in a continuousflow reactor with the presence of tri(propylene glycol) diacrylate (TPGDA) as a
crosslinker and dodecanethiol (DDT) with various amounts as a chain transfer
agent to prevent macroscopic gelation [173]. Branched poly(n-butyl acrylate)s with
180
Reprinted from the journal
1 3
Kermagoret et al. conducted the cobalt-mediated free-radical photopolymerization of vinyl acetate (VAc) or vinyl acetate/1-octene (VAc/1-Oct) in
a microreactor with ultraviolet irradiation [170]. The alkyl cobalt(III) adduct
([Co(acac) 2 (CH(OAc)–CH 2 ) <4 R 0 ] was used as the initiator of this polymerization,
which generated the radicals in the presence of light. Their results demonstrated
that the microreactor technology not only benefited the preparation of highly pure
poly(vinyl acetate) but also significantly accelerated the polymerization process. In
the preparation of poly(vinyl acetate) by ultraviolet photopolymerization, the conventional batch reactor produced a large part of side products. Interestingly, when
the reaction was carried out in the microreactor, poly(vinyl acetate) was obtained
with a well-defined monomodal mode. This photomicroreactor system was further applied for the copolymerization of vinyl acetate with reactive olefins (e.g.,
1-octene) with the help of iniferter.
Johnson and Chen constructed simple, scalable, and efficient continuous-flow
microreactor systems for the photo-controlled living radical polymerization with the
use of trithiocarbonate (TTC) as an iniferter to produce telechelic poly(N-isopropylacrylamide) (pNiPAAm) and relevant block-polymers [171]. It was proven that
metal-free and switchable photopolymerization could be achieved under flow conditions. Compared to the photo-controlled living radical polymerization in the batch
reactor, the microreactor could accelerate the preparation of polymers with high
molecular weights (e.g., 109,400 g mol
−1
). Cycles of on/off photo-controlled living
radical polymerization in a continuous-flow microreactor confirmed that externally
stimulated light acted as a function of controlled living polymerization (see Fig. 13).
Notably, this photomicroreactor setup could be easily alternated for reactions with
different monomer/TTC ratios enabling control over the molecular weights and
molecular weight distributions. It was claimed that the operational simplicity of
such a continuous-flow technique and its ability to produce high-quality polymers
in a scalable fashion would make it a useful strategy for both academia and industry.
Recently, Melker et al. reported the synthesis of poly(methyl methacrylate)
through the controlled-radical polymerization of Ir-catalyzed photooxidation reduction in a microreactor [172]. In this process, ethyl α-bromophenyl acetate was used
as an initiator, which could induce the MMA polymerization under the visible
light illumination. In particular, different capillary microreactors constructed with
four widely used tube materials including PFA, FEP, tetrafluoroethylene (Tefzel),
and ethylene chlorotrifluoroethylene (Halar) were applied for this photo-mediated polymerization. It was found that the use of the Halar capillary microreactor
with low oxygen permeability was critical for the successful implementation of
this photopolymerization. A first-order kinetics was revealed in both conventional
batch reactors and microreactors, and the polymerization rate with the continuousflow processing was increased by at least 50% compared to conventional batch
polymerization.
Eckardt et al. reported the synthesis of branched poly(butyl acrylate)s using the
photo-induced free-radical polymerization of (n/t)-butyl acrylate in a continuousflow reactor with the presence of tri(propylene glycol) diacrylate (TPGDA) as a
crosslinker and dodecanethiol (DDT) with various amounts as a chain transfer
agent to prevent macroscopic gelation [173]. Branched poly(n-butyl acrylate)s with
180
Reprinted from the journal