Preparation Of Core - Shell Type Organic - Organic Composite Microspheres Based On Microgel Template Method

Core-shell structure materials are a kind of composite materials that composed of central particles as "core" and different components as "shell" layers. The preparation and application research of core-shell structure materials have aroused many scientist's interests because of their controllable and tunable special features in composition, structure, and surface properties. Template methods have been extensively used for preparing core-shell structure materials due to their simplicity, high repeating ration, being foreseeable, uniform product morphology, and stable properties. Template can be divided into organic and inorganic types according to their chemical compositions. Organic template have become one of an effective approach for synthesis core-shell materials based on their structure's diversity and size's controllability. Compared with other organic templates, polymer microgels have become a kind of ideal template material for preparing micro- or nano- composites with special morphologies and properties. This is because polymer microgels have the advantages of simple synthesis, adjustable chemical functionality, and the controllable sizes. In addition, polymer microgels have stimulus-responsive volume changes, where the stimuli could be temperature, pH, electric and magnetic fields, etc.Based upon the previous work in our group, in this study, we focus on research interest on the synthesis of organic-organic composite microspheres with special surface structures using the polymer microgel template. Polyacrylamide (PAM) microgels were produced by the inverse suspension polymerization technique using acrylamide as monomer. Two types of Urea-formaldehyde resin (UF Resin)/PAM composite microspheres with different surface morphologies were prepared by conducting the polycondensation between formaldehyde and urea via controlling the different reaction conditions. This thesis includes two parts as follows:(1) Polyacrylamide microgels were produced by the inverse suspension polymerization technique. The UF Resin/PAM composite microspheres with novel surface morphology were prepared via polycondensation between formaldehyde and urea in the inverse suspension system using PAM as a reaction template. It was demonstrated that the surface morphologies of the composite microspheres could be controlled by varying the pH value and concentrations of the formaldehyde and urea solutions, the molar ratio of formaldehyde to urea and the composition of the used template.(2) Using PAM mierogel as template, the UF Resin/PAM composites microspheres with typical core-shell structure were prepared by in-situ polycondensation of formaldehyde and urea between the microgel and gas interface under the stated temperature. The research results indicate that the as-prepared composite microspheres with raspberry-like morphologies could be obtained by controlling the pH value and concentrations of the formaldehyde and urea solutions, the molar ratio of formaldehyde to urea and the composition of the used template. The approach we proposed is characteristics of facile and mass.The morphologies, the structure and the composition of composite microspheres were characterized by scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and Fourier transform infrared spectrometer (FTIR) techniques, respectively.