STUDIES ON PREARATION OF GRAFTED PARTICLES OF PHEMA/SiO2 AND THEIR 8-HYDROXYQUINOLINE-FUNCTIONALIZATION TRANSFORM

Micron-sized silica gel particles were surface-modified with coupling agent gamma-aminopropyltrimethoxysilane (AMPS), obtaining the modified particles AMPS-SiO2. A redox initiating system was constituted by the amino groups on the surface of AMPS-SiO2 particles and persulfate in the solution, and the surface-initiated graft-polymerization of 2-hydroethyl methacrylate was performed, resulting in the grafted particles PHEMA/SiO2. Subsequently, a polymer reaction of the grafted PHEMA was carried out, and it was the nucleophilic substitution reaction between the hydroxyl group of the grafted PHEMA and the chloromethyl group of 5-chloromethyl-8-hydroxyquinoline (CHQ). As a result, the 8-hydroxyquinoline-functionalization transform of the grafted PHEMA was realized, obtaining the functional composite particles HQ-PHEMA/SiO2. The two kinds of particles were characterized by several methods. In this work, the graft-polymerization mechanism for the amino group-persulfate initiation system was mainly investigated, and the mechanism of the substitution reaction between the hydroxyl group of the grafted PHEMA and the chloromethyl group of CHQ was also explored in depth. Finally, the chelating adsorption property of HQ-PHEMA/SiO2 for heavy metal ions was preliminarily examined. The experimental results show that the amino group-persulfate initiation system has very high initiation activity, and it can effectively initiates the graft-polymerization of HEMA on silica gel particles. At room temperature (30 degrees C), the grafted particles PHEMA/SiO2 with high grafting degree (40 g/100 g) can obtained. The substitution reaction between the hydroxyl groups of the grafted PHEMA and CHQ has a reaction mechanism of S(N)1, and using the solvent with strong polarity is advantageous to the reaction. The functional particles HQ-PHEMA/SiO2 possess very strong chelating adsorption ability for heavy metal ions. The functional composite particles are promising and potential in the analysis and separation fields.