Selective Adsorption and Steric Recognition by Molecularly Imprinted Polymers: a Study on Molecular Self-Assembly and its Effect on Selectivity

Abstract

This article presents an interesting study on molecular self-assembly and its effect on steric recognition by molecularly imprinted polymers. With S-naproxen as the template and acrylamide as the functional monomer, the self-assembly appears to play important roles in the selective adsorption, affecting not only the adsorption amount but also the enantioselective recognition. Both of them become evident by the change of monomer-template ratio. An increase in the monomer-template ratio will result in a higher level of adsorption. The best selectivity for steric recognition is, however, shown at an optimal composition (corresponding to the saturation interaction of monomer and template). A higher or lower monomer-template ratio leads to a dramatic decrease in this selectivity. Related information indicates that this may be a result from the matched arrangement between the binding sites and the template, which makes the binding sites capable of selectively recognizing the imprint species.

Optimal synthesis of a Ni(II)-dimethylglyoxime ion-imprinted polymer for the enrichment of Ni(II) ions in water, soil and mine tailing samples

“…The optimal monomer to template molar ratio that was obtained from Run 7 was 0.6:1.0, which differed from the 2.83:1.0 to 5.0:1.0 reported for other studies (Yan and Ramström, 2005;Yu and Mosbach, 2000;Zhang and Li, 2006;He et al, 2007;Kim and Spivak, 2003;Andersson et al, 1999;Chu and Lin, 2003;Spivak, 2005), or the 2.0:1.0 that was used without optimisation (Rammika et al, 2011). The optimal 265 molar ratio of NiSO 4 .6H 2 O to 4-VP to DMG was 1:0.6:3.6 which is slightly different from the predicted value of 1:2:2 (similar to that for Run 2; Table 3) or 1:2:4, the ratio that was employed with nickel chloride hexahydrate to 2-(diethylamino) ethyl methacrylate to 8-hydroxyquinoline (Romani et al, 2009 a ).…”

“…The most important parameters that determine the performance of IIPs are the molar ratios of crosslinkers to monomers (Yan and Ramström, 2005;Zhu et al, 2007;Yu and Mosbach, 2000;He et al, 2007;Spivak, 2005), monomers to template (Yan and Ramström, 2005;Yu and Mosbach, 2000;Yilmaz et al, 1999;Zhang and Li, 2006;He et al, 2007;Kim and Spivak, 2003;Andersson et al, 1999;Spivak, 2005), the volume and type of porogen (Yan and Ramström, 2005;Yu and Mosbach, 2000;Song et al, 2009;He et al, 2007;Yoshizako et al, 1998;Spivak, 2003) and the initiator used (Piletska et al, 2009;Mijangos et al, 2006;Yanagihara et al, 1999). The volume/mass of template used ought to be optimised, because increasing the concentration of the components in the polymerisation mixture will favour an increase in the pre-polymer complex, according to Le Chatelier's principle.…”

“…There are several factors that influence the polymerisation, and hence the subsequent performance of the IIPs. These factors include the nature and masses of monomers Yu and Mosbach, 2000;Okutucu and Telefoncu, 2008;Piletska et al, 2009;Yilmaz et al, 1999;Zhang et al, 2005;Zhang and Li, 2006;Song et al, 2009;He et al, 2007;Kim and Spivak, 2003;Andersson et al, 1999), crosslinkers (Wulff and Sarchan, 1972;Yan and Ramström, 2005;Zhu et al, 2007;Yu and Mosbach, 2000;Okutucu and Telefoncu, 2008;Piletska et al, 2009;Yilmaz et al, 1999;Zhang et al, 2005;Zhang and Li, 2006;Song et al, 2009;He et al, 2007;Kim and Spivak, 2003;Andersson et al, 1999;Holland et al, 2010;Mijangos et al, 2006), porogen (Arshady andMosbach, 1981 andWulff andSarchan, 1972;Yan and Ramström, 2005;Zhu et al, 2007;Yu and Mosbach, 2000;Okutucu and Telefoncu, 2008;Holland et al, 2010;Mijangos et al, 2006;Yoshizako et al, 1998), template (Yilmaz et al, 1999;Zhang and Li, 2006;He et al, 2007;…”

“…There are several approaches that can be used to optimise these parameters (Yu and Mosbach, 2000;Okutucu and Telefoncu, 2008;Piletska et al, 2009;Yilmaz et al, 1999;Zhang et al, 2005;Zhang and Li, 2006;Song et al, 2009;He et al, 2007;Kim and Spivak, 2003;Andersson et al, 1999;Holland et al, 2010;Mijangos et al, 2006;Yoshizako et al, 1998;Chu and Lin, 2003). Most have reported an approach where a single parameter was varied with others kept constant Zhang et al, 2005;Zhang and Li, 2006;Song et al, 2009;Kim and Spivak, 2003;Holland et al, 2010 Yoshizako et al, 1998;Chu and Lin, 2003). However, other groups varied more than one parameter at a time Okutucu and Telefoncu, 2008;Piletska et al, 2009;Yilmaz et al, 1999;Andersson et al, 1999).…”

“…The monomer complexes with the template, and the process is dependent on the concentration of the monomer. Adsorption processes are usually modelled using the Langmuir, Freundlich and Temkin models (Zhang and Li, 2006). The Temkin model is generally accepted as the most suitable model for chemical adsorption.…”