Sorption behaviors and relation between selectivity and possible cavity shapes of the molecularly imprinted materials

Abstract

Molecular imprinted materials (MIP) were prepared through the phase inversion process after polymerization between sol-gel particles of triethoxy orthosilicate/3-(trimethoxysilyl)propyl methacrylate and mixture of styrene/acrylic acid. The sol-gel particles were rapidly precipitated by the addition of dilute NaCl solution. After removing NaCl and NH4OH, the precipitated sol-gel particles were polymerized with two different mixtures of styrene/acrylic acid (5/1 and 10/1 ratios) in dioxane to prepare the corresponding sol-gel composites, which differ in the average length of styrene segments in-between carboxyl groups. The composites dispersed in dioxane were adsorbed with template until completing the complexation with functional groups, and then MIPs were prepared through the phase inversion process by the addition of non-solvent, H2O. The relationship between the distribution of binding cavity shapes and the selectivity of MIP was considered depending on the length of styrene segments per one carboxyl group of MIP. The MIP of the longer styrene segment per one -COOH (10/1 of styrene/acrylic acid) showed higher selectivity than the shorter one (5/1 of styrene/acrylic acid). This can be explained by the higher proportion of the cavity shapes that surround completely template for the specific binding of the template. Langmuir isotherm described all the sorption data well suggesting that the sorption in these MIPs was mainly accomplished in monolayer. Scatchard analysis revealed that the sorption sites were heterogeneous for the template.