93
film casting and subsequent phase inversion (Ulbricht 2004; Silvestri et al. 2006;
Boysen et al. 2017). In this approach, the synchronization of film imprinting and
solidification process are of critical importance for the function, the shape and the
structure of MIM.
Apart from the abovementioned strategies, Cowieson et al. (2013) demonstrated
that poly(ethylene) membranes could also be grafted with thin MIP films using
plasma-induced in situ polymerization. The plasma treatment parameters were optimized in order to achieve a balance between ablation and polymerization processes.
The grafted atrazine MIP allowed to differentiate atrazine from structural analogues
such as simazine (Cowieson et al. 2013).
With respect to phase inversion methods, evaporation of the polymer solvent (dry
phase separation) or the precipitation of the pre-synthesized polymer (wet phase
inversion process) can be used. This strategy involves the dispersion of a preformed
imprinted polymer into a matrix and subsequent membrane formation. Asman et al.
(2012) synthesized by this process, a MIP membrane by hybridizing MIP with cellulose acetate or poly(sulfone) polymers selected as supports. More recently, the
generation of hybrid-imprinted membranes with specific molecular recognition for
theophylline has been proposed. Permeability values in the developed membranes
increased with the amount of MIP, which was attributed to a rearrangement of polymer chains of the membrane due to the presence of MIP particles during membrane
formation (Algieri et al. 2018).
Composite membranes have attracted considerable attention in research, since
they combine mechanical properties of the starting membrane and outstanding
selectivity of MIPs. Macroporous composite membranes can be functionalized with
MIP to achieve high performance MIM. The base membrane structure can be used
to adapt both the pore size (permeability) and internal surface area (bonding capacity) (Ulbricht 2004). With this in mind, Renkecz et al. (2012) described a novel
approach to prepare composite membranes incorporating micro- or NPs imprinted
into commercial filtration membranes. Molecularly imprinted particles were formed
in situ in the pores of the support membrane (Renkecz et al. 2012). On the other
hand, a selective MIP membrane for the pesticide monocrotophos was prepared by
in situ polymerization on Nylon-6 membranes (Zhu et al. 2006).
MIP membranes can also be considered as alternative to traditional MIP particles
for sensing applications. From this point of view, polyvinyl chloride (PVC) membranes have been widely used to assemble MIP NPs with electrochemical transducers. Very often, the MINs are mixed with a plasticizer in a volatile solvent such as
tetrahydrofuran, and after drying, a membrane is formed having the immobilized
NPs. This approach is quite common to integrate NPs into potentiometric sensors
(Basozabal et al. 2014; Smolinska-Kempisty et al. 2017).
Other immobilization approaches include the use of self-assembled monolayers
(SAM) to design sensing elements (Wang et al. 2010). In SAM formation, the functionalized molecules are suitably assembled on a solid surface to form a densely packed
monolayer and covalently anchored. Since SAM are very stable, physically adsorbed
or unreacted molecules can be easily removed without affecting the monolayer. Two
main approaches can be used to immobilize polymers on SAMs, namely the ‘grafting
to’ and the ‘grafting from’ approaches. In the former, a polymer is grafted into the
5 Plastic Receptors Developed by Imprinting Technology as Smart Polymers Imitating…
film casting and subsequent phase inversion (Ulbricht 2004; Silvestri et al. 2006;
Boysen et al. 2017). In this approach, the synchronization of film imprinting and
solidification process are of critical importance for the function, the shape and the
structure of MIM.
Apart from the abovementioned strategies, Cowieson et al. (2013) demonstrated
that poly(ethylene) membranes could also be grafted with thin MIP films using
plasma-induced in situ polymerization. The plasma treatment parameters were optimized in order to achieve a balance between ablation and polymerization processes.
The grafted atrazine MIP allowed to differentiate atrazine from structural analogues
such as simazine (Cowieson et al. 2013).
With respect to phase inversion methods, evaporation of the polymer solvent (dry
phase separation) or the precipitation of the pre-synthesized polymer (wet phase
inversion process) can be used. This strategy involves the dispersion of a preformed
imprinted polymer into a matrix and subsequent membrane formation. Asman et al.
(2012) synthesized by this process, a MIP membrane by hybridizing MIP with cellulose acetate or poly(sulfone) polymers selected as supports. More recently, the
generation of hybrid-imprinted membranes with specific molecular recognition for
theophylline has been proposed. Permeability values in the developed membranes
increased with the amount of MIP, which was attributed to a rearrangement of polymer chains of the membrane due to the presence of MIP particles during membrane
formation (Algieri et al. 2018).
Composite membranes have attracted considerable attention in research, since
they combine mechanical properties of the starting membrane and outstanding
selectivity of MIPs. Macroporous composite membranes can be functionalized with
MIP to achieve high performance MIM. The base membrane structure can be used
to adapt both the pore size (permeability) and internal surface area (bonding capacity) (Ulbricht 2004). With this in mind, Renkecz et al. (2012) described a novel
approach to prepare composite membranes incorporating micro- or NPs imprinted
into commercial filtration membranes. Molecularly imprinted particles were formed
in situ in the pores of the support membrane (Renkecz et al. 2012). On the other
hand, a selective MIP membrane for the pesticide monocrotophos was prepared by
in situ polymerization on Nylon-6 membranes (Zhu et al. 2006).
MIP membranes can also be considered as alternative to traditional MIP particles
for sensing applications. From this point of view, polyvinyl chloride (PVC) membranes have been widely used to assemble MIP NPs with electrochemical transducers. Very often, the MINs are mixed with a plasticizer in a volatile solvent such as
tetrahydrofuran, and after drying, a membrane is formed having the immobilized
NPs. This approach is quite common to integrate NPs into potentiometric sensors
(Basozabal et al. 2014; Smolinska-Kempisty et al. 2017).
Other immobilization approaches include the use of self-assembled monolayers
(SAM) to design sensing elements (Wang et al. 2010). In SAM formation, the functionalized molecules are suitably assembled on a solid surface to form a densely packed
monolayer and covalently anchored. Since SAM are very stable, physically adsorbed
or unreacted molecules can be easily removed without affecting the monolayer. Two
main approaches can be used to immobilize polymers on SAMs, namely the ‘grafting
to’ and the ‘grafting from’ approaches. In the former, a polymer is grafted into the
5 Plastic Receptors Developed by Imprinting Technology as Smart Polymers Imitating…