Molecularly imprinted polymers prepared by precipitation polymerization and used for inducing crystallization of oleanolic acid in supercritical CO2

In the present paper, molecularly imprinted polymers (MIPs) were prepared by precipitation polymerization, using oleanolic acid (OA) as template, acrylamide (AM) as functional monomer, ethylene glycol dimethacrylate (EGDMA) as cross-linker and azobisisobutyronitrile (AIBN) as initiator in a mixture solvent of chloroform and methanol. The influence of the ratio of template molecule, functional monomer and cross-linker on the MIPs was investigated. Scanning electron micrograph (SEM), laser diffraction particle size analyzer and Fourier transform infrared spectroscopy (FT-IR) were used to characterize the MIPs. The optimum ratio of template molecule, functional monomer and cross-linker was 1:4:20. The average size of the MIPs was 23 pm. Through the adsorption kinetic experiments, the static adsorption experiments and the specific adsorption experiments, it was found that the MIPs had good specific selectivity. The MIPs were used for inducing crystallization of OA in supercritical CO2. The crystallization rate of OA reached 93.1%, and the purity of OA was 95.7%. The results indicated that the MIPs showed good specific adsorption properties and the ability to induce crystallization of OA in supercritical CO2. (C) 2011 Elsevier B.V. All rights reserved.