Importance of Functional Monomer Dimerization in the Molecular Imprinting Process

Abstract

H NMR spectra were recorded on a Varian 300 MHz NMR at ambient temperature. Chemical shifts (ppm) were referenced to tetramethylsilane or residual protonated solvent. UV measurements were made using a Jasco V-530 spectrometer. Solvents were purchased from Sigma-Aldrich, Fisher, VWR, and were purified and dried by passing through a PURE SOLV® solvent purification system (Innovative Technology). Deuterated solvents were purchased from Cambridge Isotope Laboratories. All other reagents were purchased from Sigma-Aldrich and were used as received. Surface area and nitrogen adsorption isotherms were calculated using the Brunauer-Emmett-Teller (BET) model. Gas adsorption studies were carried out using Quantachrome Autosorb Automated Gas Sorption System. 1.1 Jobʼs plot of EA9A and MAA Continuous variation analysis (Jobʼs plot) at 8.5 mM in CD 3 CN showed MAA to EA9A stoichiometry between 2:1 and 1:1. To determine the stoichiometry, data points on each side of the maximum chemical shift was fitted to a straight line. The x-value at cross point was analytically determined from the equations from the fitted lines. Measurement of Jobʼs plot was not possible at concentration higher than 8.5 mM due to the solubility limit of EA9A in acetonitrile. Although carboxylic acids such as MAA can form higher order (2:1 and 3:1) complex with adenine guests such as ethyl adenine-9-acetate (EA9A), the first order complex will dominate in CD 3 CN because chances are slim to form higher order complexes based on the probability of placing two or three functional monomer around the template molecule.

Molecular imprinting: perspectives and applications

“…Afterwards, Zhang et al 41 explained why MAA is such a versatile monomer for molecular imprinting, and revealed that the dimerization of MAA modestly enhanced the imprinting effect, as illustrated in Fig. 3.…”

Experimental and theoretical investigation of the complexation of methacrylic acid and diisopropyl urea

“…NMR titration, a relatively common method in host-guest chemistry, was used to determine binding constants where host and guest are mixed in different ratios and the NMR spectrum of the mixture is measured. NMR titration is often used to understand complexation phenomena in macrocycle chemistry 7,8,9 , molecular imprinting 10,11 and receptors 12,13 . Due to fast-exchange correlation the NMR signals of the complexes and the initial compounds do not appear separately but as their average.…”

Imidazolium-based functional monomers for the imprinting of the anti-inflammatory drug naproxen: Comparison of acrylic and sol–gel approaches

“…The preparation of molecularly imprinted polymers (MIP) typically involves three steps: first, a monomer-template [M-T] complex is formed via self-assembly; next, the M-T complex is polymerized with an excess of cross-linker to form a rigid polymer; finally, the template is removed, leaving behind binding cavities which are complementary in shape and functional group to the template [2]. The vast majority of MIP is based on the use of organic acrylate-type polymers: a standard procedure using a methacrylate monomer, with a nearly optimal ratio to the template molecule and crosslinker, is described in numerous works [2][3][4][5][6][7][8]. The broad applicability of methacrylic acid (MAA) as a functional monomer in MIP production is related to the fact that the carboxylic acid group serves well as a hydrogen bond and proton donor as well as a hydrogen bond acceptor [9].…”