The dynamics of titanium ethoxide‐doped dodecane droplet microencapsulation

Single‐droplet electrodynamic trapping is used to monitor the microencapsulation of titanium ethoxide‐doped dodecane droplets immersed in water vapor. During the evaporation of volatile dodecane, titanium ethoxide reacts with water vapor to form a titanium dioxide film at the droplet surface. The onset of film formation is determined from changes in the droplet light transmission. It is shown that the time for film formation is dependent on the droplet size, water partial pressure, and initial concentration of titanium ethoxide. The reaction dynamics is liquid phase controlled and is first order in the ethoxide concentration. The porosity of the film is determined from the effect of the film formation process on droplet evaporation, as well as from scanning electron microscopy. For initial ethoxide concentrations less than 50% by weight, microencapsulation is characterized by porous films that have no observable effect on the evaporation rate. For ethoxide concentrations exceeding 50% by weight, impermeab...