Preparation and characterization of temperature-triggered silica microcapsules containing sodium monofluorophosphate with tolerability to extreme pH

Low porosity silica microcapsules (SiO2/Sodium monofluorophosphate) were synthesised by a soft-template method in room temperature. Morphology of silica microcapsule can be controled by changing the concentration of TEOS in reinforcement phase in the range of 1%-4%. With the increased concentration, thickness of capsule raised and some rod-like structures occured. The impacts of oil phase volume fraction and rotation speed of emulsification on the diameter distribution of capsules were discussed. The former functioned via changing viscosity of mixed solution while the latter played a complicated role in diameter distribution. This method of microencapsulation used in our paper is easy to achieve for that the experimental conditions are mild and do not require complicated or costly instruments, which is suitable for industrial production. In addition, we also explored the changes of microcapsules under different environmental factors including temerature and pH.