In-situ Polymerization Of Styrene/Nano-SiO₂

With a progress in science and technology, materials having diversity and high functionality have been highly required. In particular, composite materials combining characteristics of each component have attracted attention. Recently the incorporation of inorganic nanoparticle fillers into polymers had been proved to be an effective way for the improvement of the mechanical properties of polymers. However, the control of the interface and the dispersion of the nanoparticle in polymeric materials were considered to be the greatest importance in these nanocomposite materials. It was required to control the aggregation to enhance the interfacial interaction between different materials.In this thesis, firstly, the property of the commercial nano-Si02 was investigated. According to the result of TEM, SEM and the Coulter LS particle size analyzer, it was found that the particles of the commercial nano-SiO, were in the state of aggregation, and their diameter was over the range of nanometer (1300-l400nm). The purpose of the research was to separate the aggregation and to modify the surface of the commercial nano-Si02.An in-situ emulsion grafting polymerization method was applied to modification of the commercial nano-Si02 particles, and the modified nano-Si02 can be added to polymeric materials for improving their mechanical performance using existing compounding techniques. The dynamics of the in-situ emulsion grafting polymerization of styrene (St) in the presence of the commercial nano-Si02 were studied. Surfactants used were sodium dodecyl sulfate (SDS) and capryl phenyl polyoxyethylene ether (OP-lU). The effect of the surfactants concentration, monomer concentration, reaction temperature, and quantity of the commercial nanoSi02 on the diameter of particles was studied. Experimental results showed that the size of microcapsulate decreased with the increase of reaction conversion, the particles of the aggregation was exfoliated gradually. In the presence of the surfactant of SDS and OP-lU, the degree of exfoliation was good and the stability ofiiithe emulsion was also very good.The TEM photograph showed that the microcapsulate had the shape of core-shell and its size was in the range of nanometer. The result of Coulter Ls particle size analyzer also showed that the diameters of microcapsulate were in the range of nanometer. FTIR spectrum approved that polystyrene had been grafted on the commercial nano-Si02 surface by in-situ emulsion grafting polymerization.It was found that the diameter of the modified nano-Si02 could reach to 77.1 run and had good repetition. Unlike the other approaches for modification of nanoparticles, the current technique had many advantages, such as simpleness, low cost, easiness to be controlled.