The Preparation And Characterization Of Molecular Imprinted Polymeric Spheres Using PAMAM-Silica

Molecular imprinting technology is a useful method of function polymer material preparation and it has aroused people's widespread interest to the field of special selectivity. This article summarized the recent development of the molecular imprinting polymer, polyamido-amine (PAMAM) and PAMAM modified silica. It simply introduced the basic principle of molecular imprinting polymer and PAMAM synthesis and emphatically introduced recent research progress in sorts, synthesis technologies, experimental implementation methods, characterization methods of the molecular imprinting polymer. This article explored a new molecular imprinting polymer - using the PAMAM modified nano silica, which provided a new way for the separation and depuration of the bio-macromolecule.In this article, firstly, we used the micro-emulsion method to prepare the nano-silica, and decorated its surface with the amino and vinyl functional groups. Then, we used the amino groups modified silica as the original sites and carrier to precede the dendrimer grafting through the divergent method. The molecular imprinting polymers (MIP) was prepared in a suspension process using methacrylic acid (MAA) as the functional monomer, PAMAM modified silica as the support and functional co-monomer, L-tryptophan molecules as the template, trimethylolpropanetrimethacrylate (TRIM) as the cross-linker, polyvinyl alcohol (PVA) as the suspension agent.Scanning electron microscope (SEM) was chosen to detect the micro-structure of the molecular imprinting polymer; Fourier transforms infrared spectrum (FT-IR), Zeta potential analyzer, thermogravimetric analyzer (TG) were used to confirm the success of the PAMAM modification by the absorption peak, superficial electric properties and the weight changing process of the PAMAM modified nano-silica; elemental analyzer was chosen to calculate the number of the amino groups on the surface of the silica. The result indicated that the silica was covered capsule shape PAMAM comparing with the pure silica, the modified silica obtained the characteristic absorption peak of PAMAM at 1558,1647cm-1, the surface got 25mV positive charge and the amino groups on the surface was approximately 4.44mmol/g.SEM was chosen to detect the molecular imprinting polymer's exterior appearance, the internal structure and the result indicated that the structure of the resulting product was porous like "crumb", which would benefit the mass transfer in the adsorption process. The static adsorption, dynamic adsorption, high performance liquid chromatography were applied to identify the separation ability of the MIP, using L-tyrosine (Tyr), the L-phenylalanine (Phe), the L-histidine (His) as the competitive substrate. The result showed that the MIP prepared using the PAMAM silica as the functional co-monomer, which was modified with the hydrophilic PAMAM, bore quick mass transfer speed, big adsorption capacity. Simultaneously, in the HPLC experiment, 90% water and 10% methanol was used as the flow phase, where good separation result was obtained.In all, MIP prepared based on the PAMAM modified silica will be the prospect of the widespread application in separation, purification of the bio-macromolecules as well as in the domain of HPLC.