Porous Silica Hollow Microspheres And Its Pesticide Release Behavior

Now, with the research development in field of catalysis chemistry and bioengineering, people are exploring polymer and organic/inorganic composite microspheres with various morphologies, structures and sizes. Recently, template method on Preparation of composite materials with special structure and properties has become the focus of active research. The template method is superior to other approaches, in which the size, structure and morphology of the prepared materials can be controlled and adjusted by simple altering the nature of template and the preparation conditions. Moreover template can be predesigned in the size and shape of objective materials. Based on the idea mentioned above, the research in this thesis includes the following Parts.(1) First, the polyacrylamide (PAM) micro-gels with a diameter of about 30-60μm are prepared by inverse suspension polymerization method, and then we took advantage of three-dimensional network structure of the polyacrylamide (PAM) micro-gels, and in rich solvent with the swelling behavior, and porous PAM micro-gels are prepared by the freeze-drying treatment of the swollen micro-gels. Secondly, PAM/SiO2 composite microspheres with hierarchical surface morphologies are prepared utilizing the porous PAM micro-gels as templates. The morphology, composition, and micro-pore parameters of the microspheres were characterized by scanning electron microscopy (SEM), thermo-gravimetric analysis (TGA), Fourier transform infrared spectroscopy (FI-IR), N2 absorption analysis, respectively. The results indicated that deposited on the silica composite microspheres increased with the amount of silica seed solution increased.(2) Utilizing the porous PAM micro-gels as templates, PAM/SiO2 composite microspheres are prepared the porous polyacrylamide (PAM) micro-gels immersed with tetraethoxysilane (TEOS) anhydrous alcohol solution and water in a moist atmosphere, with ammonium hydroxide as a catalyst. The hollow porous silica spheres with controllable surface morphologies have been synthesized through calcination of the PAM/SiO2 composite microspheres at 550℃for 4 h. The morphology, composition, and crystalline structure of the microspheres were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermo-gravimetric analysis (TGA), Fourier transform infrared spectroscopy (FI-IR), and X-ray diffraction (XRD), N2 absorption analysis, respectively. The results showed that the precursor TEOS volume and concentration of ammonia catalyst of hollow porous silica pore structure and surface morphology have a significant impact. With the increase in the volume of TEOS and ammonia concentration, porous silica hollow microspheres of surface area and pore volume are gradually reduced, and also slightly increased diameter. Moreover, this shows that the surface of hollow porous silica morphology also had a huge change. Although the surface morphologies of the composite microspheres are varied, the morphologies are typically divided into three categories:①an ideal flower surface;②a porous wrinkly morphology;③a wrinkly surface.(3) The hollow porous SiO2 and PAM/SiO2 microspheres were applied as controlled pesticide release carriers to study the effects of the different carriers on the loading efficiency for fomesafen. The results showed that the porous silica hollow microspheres as carriers for controlled release of pesticides better effect than to PAM/SiO2 composite microspheres as carriers for controlled release of pesticides.