Molecular Imprints Frozen by Strong Intermolecular Interactions in Place of Cross‐Linking

Abstract

A new way to freeze molecular imprints in a polymer material is reported. So far, molecular imprinted polymers (MIP) involve copolymerization of a functional monomer and large amounts of cross‐linking agent, which keeps the template shape memory in rigid molecular imprints. MIP materials are prepared herein without cross‐linking agent. Stiff chains of polyaniline grafted on a solid support as a brush‐like material achieve the necessary rigidity. Differential adsorption to imprinted and non‐imprinted materials provides evidence of molecular imprints. A correct adsorption isotherm for mobile adsorbed layers (Volmer isotherm) is introduced instead of the popular but inadequate Langmuir isotherm. Non‐selective adsorption is entropic, whereas adsorption to molecular imprints has an enthalpic contribution coming from specific interactions. Fast adsorption kinetics are a definite benefit with regards to applications such as chromatographic separations and chemical sensors.

Design of molecularly imprinted polymer materials relying on hydrophobic interactions

“…The surface imprinting technique was chosen to overcome some drawbacks such as accessibility to adsorption sites. Indeed, a thin layer of MIP bound to the surface of a porous solid support improves the accessibility to the recognition sites and accelerates adsorption kinetics [6,[25][26][27][28][29], As an example, a thin MIP coating bound to silica powder has been implemented in standard SPE cartridges for the selective pre-concentration of the patulin toxin from apple juices matrices in usual conditions of analysis [28]. As another example, a thin layer of imprinted PANI was immobilized to the porous silica surface by copolymerization of grafted and free aniline for the selective adsorption of the benzophenone-4 sunscreen [27,29].…”

“…3-MPTMS was covalently attached to the surface of silica nanoparticles by means of a condensation reaction between surface silanol groups of silica and methoxy groups of 3-MPTMS. The resulting SiO2@MPTMS material was characterized by 13 C and 29 Si NMR and FTIR spectroscopy, thermogravimetric analysis and elemental analysis reported in details in the Supplementary Information file, and Raman spectroscopy.…”

“…Scatchard plots of experimental data of the MIP and NIP materials in are too much scattered to allow accurate calculations of binding constants and Qmax. Scatchard plots just gave evidence of the existence of two kinds of binding sites for the MIP and only one kind of binding site for the NIP [29]. The Scatchard model and its underlying Langmuir model consider adsorption to binding sites.…”

“…The relevant thermodynamic model is a combination of adsorption on molecular imprints considered as specific sites and non-specific adsorption as a mobile layer. Such thermodynamic approach has recently been introduced as the Langmuir−Volmer model [29]. So, the adsorption on NIPs was modelled using the Volmer adsorption isotherm and adsorption on MIPs was modelled using the Langmuir−Volmer adsorption isotherm.…”

“…They are quite popular because of the simplicity of their mathematical expressions [49,50]. The Volmer and Langmuir models generally fit the experimental data equally well [29]. The fit of the Langmuir isotherm to the NIP data is not so good, as revealed by the poor match of experimental data to a linear behavior in the Scatchard plot.…”