Semi-Covalent Imprinting

C. Ring-Opening Metathesis Polymerization with a Semi-Covalent Imprinting Strategy... 

Caro E et al (2002) Non-covalent and semi-covalent molecularly imprinted polymers for selective on-line solid-phase extraction of 4-nitrophenol from water samples. J Chromatogr A 963(1-2) 169-178... 

Figure 2.3 Semi-covalent molecular imprinting of cholesterol using the sacrificial spacer approach. Polymerization (1) cleavage and extraction (2) rebinding (association) (3) and dissociation (4).

The imprint is achieved by arranging polymerizable functional monomers around a guidable template, and the complexes are formed through covalent, non-covalent, or semi-covalent interactions between the template and monomers... 

The semi-covalent approach combines the advantages of the previous two methods, employing reversible covalent bonds in the imprinting step and noncovalent interactions in the recognition process, after the cleavage of the template from the polymer. 

This in turn leads to a much broader range of applicability compared to covalent and semi-covalent techniques. The diversity of target compounds that have been imprinted using noncovalent techniques is vast and a brief general overview of substance classes is listed in Table 2. Finally, compared to covalent techniques, the noncovalent approach utilizes interactions that are more similar to those seen in natural, biochemical processes. Thus, the noncovalent approach is regarded as the most promising technique for mimicking nature s selectivity. 

One consequence of the uniform binding site distribution and high capacity of these polymers is that they may be rather better suited to the preparation of chromatographic (HPLC) stationary phases than noncovalently imprinted materials. In fact this was the conclusion arrived at by Hwang and Lee [15], who compared the chromatographic performance of cholesterol-imprinted polymers prepared by the semi-covalent (carbonate spacer) method with noncovalent MIPs incorporating... 

The semi-covalent" and sacrificial spacer approaches of imprinting bear similarities to the covalent imprinting approach, at least in the imprinting step, where the template is covalently bound to the functional monomer. In the latter approach, labile covalent bonds, such as carbonates... 

MIPs can be synthesized following three different imprinting approaches named covalent, non-covalent and semi-covalent procedure, according to the kind of interaction between a template and functional groups during the synthesis and recognition phases (Caro et al., 2002). 

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