Miniemulsion Polymerization And Its Application In Preparation Of Polymer Nanocomposite

Miniemulsion polymerization was developed in 1970s. Due to their small size, monomer droplets are the main nucleation locis in miniemulsion polymerization. This will extend the application of conventional emulsion polymerization. Therefore, any effort on the development of this new technique will be urgent and meaningful.In present study, the miniemulsion polymerizations of styrene emulsified by sodium dodecyl sulphate (SDS) and co-stabilized with hexadecane (HD) were carried out. The sizes of monomer droplets and latexes were characterized by dynamic light scattering (DLS) and transmission electron microscopy (TEM). According to these data, the surface coverage and ratio of latexes number and droplets number (Np/Nm) were both calculated. Then the dependence of nucleation mechanism and kinetics on the process parameters was investigated. Results show that, the nucleation mechanism and polymerization rate are mainly affected by SDS concentration and HD level. The dominant droplet nucleation can be achieved by careful operation. And perfect polymer particles in nanosize can be easily synthesized. Furthermore, the new technique on preparing polymer nanocomposite was developed based on these monomer droplets. The sol-gel process and radical polymerization were conducted spontaneously in monomer droplets (nano reactors) of miniemulsion. Dynamic light scattering (DLS), Fourier transform infrared (FTIR), Differential scanning calorimetry (DSC), and TEM were employed to characterize the structure and property of the products. Results indicate that the nanocomposite can be easily prepared in one step. Glass transition temperature (Tg) of composite is enhanced by increasing the inorganic content. Composites latexes with different structure can be prepared by tailoring the reaction rates of these two reactions.In order to solve the deleterious effects of HD on the properties of composite, a new miniemulsion system co-stabilized by liquid polybutadiene was developed in the second part. Moreover, the comparison of these two systems was discussed. The dependence of monomer size, latex size and knetics on LPB level is same with that of HD case. Due to the polymeric property of LPB, which can preserve the small droplets, the proportion of monomer nucleation in LPB system is higher than that of HD system. However, due to its higher viscosity, the LPB is less efficient than HD in preparing small monomer droplets. The size of monomer droplets in former system is larger than that of latter one. The results of DSC measurement indicate that LPB is chemically incorporated in the product, showing the modification on the product. The results of FTIR, DSC, Thermogravimetry (TG), X-ray diffraction (XRD) show that nanocomposite can be prepared using the LPB-costabilized miniemulsion system. This will optimize the new technique in preparing polymer composite, developed in present study. The compartment effect of the reactors (monomer droplets) enables the blending in nano size, strengthening the interaction of these two phases. Therefore, this new technique exhibits great potential in preparing polymer nanocomposite.