Miniemulsions of styrene with sodium dodecyl sulphate (SDS) as the surfactant and hexadecane (HD) as the co-stabilizer were prepared and polymerized. The on-line conductivity measurements were employed to characterize the emulsification by ultrasonication. Both the dynamic light scattering (DLS) and the transmission electron microscopy (TEM) were employed to determine the droplet and the particle size. The effects of various reaction parameters on the droplet (or particle) size and the polymerization kinetics were investigated. These parameters include the sonication time and the concentrations of SDS ([SDS]), potassium persulphate ([KPS]), and HD ([HD], as weight percent with respect to monomer). Moreover, their influence on the droplet nucleation was also discussed. It is shown that a critically steady state can be obtained after ultrasonicating the emulsion system for at least 24 min and relatively stable miniemulsions were prepared. The polymerization rate of miniemulsions increases with the increase in [SDS], [HD], and [KPS] due to different mechanisms, and the rate is faster than that of the corresponding macroemulsions. In addition, the predominant droplet nucleation is achieved in current miniemulsion systems and the required condition is concluded. Finally, nanosize polystyrene latexes were synthesized.

Miniemulsion polymerization is one of heterogeneous polymerization method that can be effectively used to synthesis of various novel organic-inorganic nanocomposite particles. This method can provide opportunity of good incorporation between the polymer and inorganic phases in the formed submicrometer-sized particles. In this article, we report preparation polystyrene/silica nanocomposite particles via miniemulsion polymerization of styrene (St). Synthesis of the nanocomposite particles were performed using g-methacryloxyprop yltrimethoxysilane (MPS) which perform compatibility of silica and the polymer phase by covalent interactions. Morphology, particle size, spectroscopic characteristics and thermal properties of resulted nanocomposite particles were studied. TEM study showed a raspberry like morphology for the nanocomposite particles. FT-IR spectroscopy confirmed the presence of polystyrene and silica with MPS compatibilizer in the structure of the nanocomposite. Thermogravimetric analysis and Differential scanning calorimetry studies showed that the incorporation of silica in polymer matrix results variation in thermal stability and glass transition temperature of nanocomposite particles relative to that of the polymer without silica in it.

High solid content nanocomposites based on poly(methyl methacrylate-co-butyl acrylate)/nanosilica was synthesized via miniemulsion polymerization in a semi-continuous operation. Oleic acid was used to act as a coupling agent between silica surfaces and polymer. Latexes with solid content of 42% were obtained, containing 5% by weight nano-SiO2 with respect to polymer. FTIR Results show the modified structure of silica with oleic acid and confirm the presence and bonding of modified silica on the polymer structure. Morphological investigations were performed using TEM analysis. The results of microscopic images confirm the nanocomposite structure where the nanoparticles of silica are coated with the polymer nanolayers. Thermal analysis including DSC and TG/DTA was used to investigate Tg, thermal stability and thermal decomposition of the samples. The nanocomposite latex is compared with the neat latex of the same monomer structure. The results of DTA analysis show an increase of about 8°C in the degradation temperature. DSC Analysis shows that the glass transition temperature of the nanocomposite is higher than that of pure acrylic latex. Moreover, the samples with improved hardness are compared with blank latex sample. All analyses demonstrate the well located silica nanoparticles inside the latex polymeric structure.