Vinyl Functional Polysiloxane Microemulsion: Preparation and Characterization

Avinyl functional microemulsion was successfully prepared via polycondensation between polysiloxane prepolymer and a modifier (vinyl silane coupling agent with alkoxy groups). The polysiloxane prepolymer was prepared by ring-opening of D4 (octamethylcyclotetrasiloxane). The structure and properties of vinyl functional microemulsion were characterized by transmission electron microscopy (TEM), Fourier transform infrared (FTIR), photon correlation spectroscopy (PCS). FTIR Spectroscopy result showed that vinyl groups were successfully introduced into the polysiloxane molecules. The variation in pH, amount of vinyl coupling agent and catalyst were studied in relation to the properties of the final microemulsion. The results indicated that under strong acidic more coagulum and higher percentage of conversion occurred in the microemulsion. TEM results also revealed that particles are densely packed in strong acidic condition but become sparsely distributed in weak acidic condition. An increase in the vinyl coupling agent content leads to an increase in formation of coagulum and in particle size, but it lowers the particle size distribution. The smaller ratio of the average surface coverage of surfactant leads to higher amount of coagulation which is in linear dependence to the increased amount of vinyl coupling agent modifier. Photon correlation spectroscopy results show that increasing the amount of vinyl coupling agent modifier increases the particles size, while reduces the particles size distribution. It can be concluded that the coagulum weight fraction increases linearly with higher amount of catalyst. An increase in the vinyl coupling agent modifier leads to an increase in the coagulum. The microemulsion shows stability when the amount of catalyst is about 3.0-4.0 wt%.