82
were also extrapolated to macromolecules by Gai et al. (2010), achieving the
imprinting bovine serum albumin (Gai et al. 2011) and lysozime (Gai et al. 2010)
on the surface of magnetite (Fe 3 O 4 ) beads using phosphate buffer as solvent. The
research on surface printing underwent a notable expansion thereafter, being mainly
applied to carbon based materials (Xu et al. 2011a; Ji et al. 2013), core-shell (Liu
et al. 2011; Zhang et al. 2013; Liu et al. 2014) and magnetic particles (Liu et al.
2012; Zou et al. 2014), membranes (Bing et al. 2011; Lu et al. 2015; Qiu et al.
2016), monoliths (Ban et al. 2013) and thin films (Sasaki et al. 2015).
Adali-Kaya et al. (2015) have contributed significantly to this field, reporting a
new iridium photoredox catalyst, which was capable of conducting photoinitiated
ATRP under mild conditions, thus widening the range of functional monomers, and
therefore, molecular templates usable in ATRP imprinting. In recent years, interest
in MIPs synthesized under ATRP polymerization continues its own expansion.
From this point of view, laser-induced metal-free ATRP has been used to graft MIP
thin films on titanium surfaces to develop sensors compatible with in vivo measurements (Ramakers et al. 2019). Other sensors having biocompatible matrices have
also been developed so far to determine, e.g. glycoproteins such as ovalbumin in
eggs (Saeki et al. 2019).
5.2.2.4 Reversible Addition-Fragmentation Chain Transfer
Polymerization
Chiefari et al. (1998) (CSIRO group) presented a new living free-radical polymerization of exceptional efficiency and versatility, namely, reversible additionfragmentation chain transfer polymerization or RAFT polymerization. This
approach is nowadays one of the most powerful CRP approaches thanks to its tolerance to a wide range of reaction conditions and functional monomers (Zhang 2013).
It also provides great control over Mw and allows reducing polymer heterogeneity
(Salian and Byrne 2013). Nevertheless, polymerization times are slow and obtaining polymers with high Mw is quite difficult (Hill et al. 2015).
RAFT polymerization is more closely associated with reactions in which thiocarbonylthio (S=C(Z)S-R) compounds are involved as chain transfer agents (RAFT
agents) (Lowe and McCormick 2007) such as dithioesters, dithiocarbamates (Moad
2019) and trithiocarbonates (Chong et al. 2003), which allow polymerization to be
controlled through a fast degenerative chain transfer of propagating radicals. In
these degenerative systems, a radical source such as a free radical initiator is
required, since the total number of radicals during the activation-deactivation process remains constant (Perrier 2017). Polymerization is initiated through the cleavage of this initiator, resulting in two active radicals, which react with the monomers
to form propagation radical species (Fig. 5.6). Very often, these initiators are conventional initiators that can be activated thermally, such as AIBN. However, other
radical sources which come from direct photolysis of the RAFT agent, redox or
even photo-redox chemistry have also been used (Moad 2017).
A. Gómez-Caballero et al.
were also extrapolated to macromolecules by Gai et al. (2010), achieving the
imprinting bovine serum albumin (Gai et al. 2011) and lysozime (Gai et al. 2010)
on the surface of magnetite (Fe 3 O 4 ) beads using phosphate buffer as solvent. The
research on surface printing underwent a notable expansion thereafter, being mainly
applied to carbon based materials (Xu et al. 2011a; Ji et al. 2013), core-shell (Liu
et al. 2011; Zhang et al. 2013; Liu et al. 2014) and magnetic particles (Liu et al.
2012; Zou et al. 2014), membranes (Bing et al. 2011; Lu et al. 2015; Qiu et al.
2016), monoliths (Ban et al. 2013) and thin films (Sasaki et al. 2015).
Adali-Kaya et al. (2015) have contributed significantly to this field, reporting a
new iridium photoredox catalyst, which was capable of conducting photoinitiated
ATRP under mild conditions, thus widening the range of functional monomers, and
therefore, molecular templates usable in ATRP imprinting. In recent years, interest
in MIPs synthesized under ATRP polymerization continues its own expansion.
From this point of view, laser-induced metal-free ATRP has been used to graft MIP
thin films on titanium surfaces to develop sensors compatible with in vivo measurements (Ramakers et al. 2019). Other sensors having biocompatible matrices have
also been developed so far to determine, e.g. glycoproteins such as ovalbumin in
eggs (Saeki et al. 2019).
5.2.2.4 Reversible Addition-Fragmentation Chain Transfer
Polymerization
Chiefari et al. (1998) (CSIRO group) presented a new living free-radical polymerization of exceptional efficiency and versatility, namely, reversible additionfragmentation chain transfer polymerization or RAFT polymerization. This
approach is nowadays one of the most powerful CRP approaches thanks to its tolerance to a wide range of reaction conditions and functional monomers (Zhang 2013).
It also provides great control over Mw and allows reducing polymer heterogeneity
(Salian and Byrne 2013). Nevertheless, polymerization times are slow and obtaining polymers with high Mw is quite difficult (Hill et al. 2015).
RAFT polymerization is more closely associated with reactions in which thiocarbonylthio (S=C(Z)S-R) compounds are involved as chain transfer agents (RAFT
agents) (Lowe and McCormick 2007) such as dithioesters, dithiocarbamates (Moad
2019) and trithiocarbonates (Chong et al. 2003), which allow polymerization to be
controlled through a fast degenerative chain transfer of propagating radicals. In
these degenerative systems, a radical source such as a free radical initiator is
required, since the total number of radicals during the activation-deactivation process remains constant (Perrier 2017). Polymerization is initiated through the cleavage of this initiator, resulting in two active radicals, which react with the monomers
to form propagation radical species (Fig. 5.6). Very often, these initiators are conventional initiators that can be activated thermally, such as AIBN. However, other
radical sources which come from direct photolysis of the RAFT agent, redox or
even photo-redox chemistry have also been used (Moad 2017).
A. Gómez-Caballero et al.