Facile fabrication of hollow molecularly imprinted polymer microspheres via pickering emulsion polymerization stabilized with TiO2 nanoparticles

The polymer microspheres with hollow structure are of technological importance in the removal of pollutants because of the large specific surface area and low mass transfer resistance. In this work, we employ the Pickering emulsion polymerization stabilized with TiO2 nanoparticles to build the molecularly imprinted polymers microspheres with hollow structure (H-MIPs) for the precise recognition of dibutyl phthalate (DBP), which would influence the biological reproductive system and endocrine system as a typical endocrine disrupting compound. The polymerization induced phase separation occurring within Pickering emulsion droplets plays a significant role in the formation of hollow structure. The morphology and structure of H-MIPs were observed via optical microscope and field emission scanning electron microscope, respectively. The results indicate that H-MIPs microspheres are of irregular spherical form with sunken surface and perfect hollow structure. The forming process of the hollow structure was analyzed in detail. Besides, the chemical structure and thermal stability of H-MIPs and H-NIPs were characterized by fourier transform infrared spectroscopy and thermal gravimetric analysis, respectively. The binding performance of H-MIPs and H-NIPs was investigated through a series of binding experiments, which consist of the binding kinetics, binding isotherm, selective test and reusability experiment. The results show that H-MIPs microspheres exhibit remarkable binding kinetics towards DBP, and the saturated adsorption time is not more than 30 min. Apart from the fast binding rate, H-MIPs also show considerable binding amount, accurate binding selectivity and good regenerability. The imprinting factor could reach to 2.56, and the binding amount towards DBP remains at a relatively high level within 3 cycles. The prepared H-MIPs microspheres have broad application prospects in environmental and analytical field involved DBP, and the study also offers an alternative method for the facile building of H-MIPs microspheres.