Miniemulsion Preparation Of Organic - Inorganic Nanoparticles And Their Film Forming Properties

In this dissertation, three types of latex particles, namely polystyrene/SiO₂ nanocomposite particles, silanol functionalized polystyrene particles and silanol functionalized poly(styrene-co-butylacrylate) particles, were successfully prepared via miniemulsion polymerization. The film-forming property of silanol functionalized poly(styrene-co-butyl acrylate) particles was also investigated.The SiO₂/ polystyrene nanocomposite particles were synthesized through miniemulsion polymerization in the presence of silica particles coated with methacryloxy(propyl)trimethoxysilane(MPS).The size and morphology of the composite particles can be tuned by adjusting the silica particle size and the surfactant concentration. For 45 nm silica particles, the number of silica particles entrapped into each latex particle gradually decreases and finally form core-shell morphology with increasing surfactant concentration from 20 mM to 40 mM.. For 90 nm silica particles, the size of the composite particles decreases from 170 nm to 130 nm with increasing surfactant concentration from 20 mM to 40 mM, but the core-shell morphology keeps unchanged. For 200 nm silica particles, the silica particles are not encapsulated by the polymer layer, instead, the latex particles adsorb on the silica surface forming "raspberry-like" morphology.Silanol-functionalized polystyrene particles were prepared through a miniemulsion copolymerization process using MPS as a functional comonomer. The hydrolysis and condensation of MPS was studied using FTIR and ²⁹Si solid-state NMR spectroscopy. The MPS was well protected from the hydrolysis and condensation reactions. It was found that the particle size was not significantly influenced by the MPS content and influenced by the surfactants concentrations. The presence of the silanol group on the latex particle surface was evidenced by 8 potential measurements and infrared spectroscopy. As expected, the higher the MPS content is, the higher the amount of silanol groups on the particle surface. A tendency of enrichment of the MPS at the particle surface with increasing the MPS content was detected by X-ray photoelectron spectroscopy (XPS).Silanol-functionalized poly(styrene-co-butyl acrylate) particles were prepared through a miniemulsion copolymerization of MPS with styrene and butyl acrylate. using AIBN or KPS as the initiator. The effects of pH value, the type of initiator and MPS content on the film-forming property of the resulted latex were studied in detail Swelling experimental results showed that the premature crosslinking of the latexparticles was significantly influenced by the initiator, the pH value but not by the MPS content. If the gel content of the latex particles was too high, the post-crosslinking mainly occurred in intraparticles, resulting in relatively poor film formation property, on the contrary, if the gel content of latex particles was fair or not very high, some post-crosslinking happened in interparticles, causing good films. The more post-crosslinking reactions from interparticles took place, the better the properties of the films were. Increasing MPS content or cured temperature could improve the properties of films.