The Preparation And Application Of PH-responsive Magnetic Polymer Microspheres

With the development of the environmental modification and biomedical research as well as some related fields, stimuli-responsive polymer microspheres as a functional material, have attracted more attention. Wherein, the yolk-shell structured multi-functional magnetic polymer microspheres have a wide range of applications such as drug delivery, environmental restoration, the micro-reactor and lithium batteries owing to its unique structure, the core and the shell easily functionalized, and the physical and chemical properties which can be modulated. Currently, the preparation methods of yolk-shell structured multi-functional magnetic polymer microspheres are mainly distillation precipitation polymerization and RAFT polymerization. However, the production rate of distillation precipitation polymerization is considerable lower than desirable, while the RAFT polymerization often results in quite thin shell. Emulsion polymerization is the most useful method to prepare magnetic polymer microspheres with high yield. However, the emulsion polymerization is generally only applicable to hydrophobic monomer. The most of stimuli-responsive polymers are generally hydrophilic one. This paper contains two parts focusing on preparation, characterization and application of yolk-shell structured magnetic polymer microspheres and anisotropic PS/SiO2composite microspheres based on emulsion polymerization.1. The preparation and application of yolk-shell structured pH-responsive Fe3O4@PMAA microspheres:First, monodisperse and uniform Fe3O4particles prepared by a one-step modified solvothermal method were coated with silica layer via a versatile sol-gel process using TEOS as a precursor. Second, the Fe3O4@SiO2particles were encapsulated in polymer via a seeded emulsion polymerization to obtain monodisperse Fe3O4@SiO2@PMMA composite microspheres. Finally, the interlayer silica of the composite microspheres was selectively dissolved by8mol L-1NaOH aqueous solution, while the PMAA shell was simultaneously formed from the hydrolysis reaction of PMMA in alkaline solution, and thus the pH-responsive yolk-shell Fe3O4@PMAA microspheres were obtained. And then we used pH-responsive Fe3O4@PMAA microspheres as adsorbent to measure the adsorption capacities for Cu2+, Pb2+, Cr3+and Cd2+. The results showed that the yolk-shell Fe3O4@PMAA microspheres exhibited a significant adsorption capacity of metal ions and the adsorption capacity of Cu2+reached to3.72mmol g-1. In addition, we used ceftriaxone sodium as a model drug to study the drug loading capacity and control release behavior of the Fe3O4@PMAA microspheres. The drug loading capacity (DLC) of the Fe3O44@PMAA microspheres was up to180%and the release behavior of the Fe3O4@PMAA microspheres was pH-dependent.2. The study of the reaction process and the effect of experiment condition on the morphology of the anisotropic PS/SiO2composite microspheres:First, we prepared monodisperse silica particles with300nm according to the well-known Stober method with slight modification, and then the surface of silica particles was further functionalized with a coupling agent [3-(methacryloxy)propyl]trimethoxysilane (MPS) through the siloxane linkage. Finally, PS/SiO2composite particles with different morphologies were produced via dispersion polymerization of styrene using MPS-modified SiO2as seeds. We studied the effect of the weight ratio of styrene/silica, reaction temperature and reaction medium on the morphologies of PS/SiO2composite microspheres as well as their formation mechanisms. It was found that the formation process was different when the weight ratio of St/SiO2was changed.