During the preparation of porous microspheres of ethyl cellulose, the oil phase solution is first mixed with saturated aqueous solution of ethyl acetate. The oil phase solution is broken into small droplets under high-speed shear and dispersed in the water phase to form an emulsion. Since the water phase is saturated with ethyl acetate, the oil phase remains liquid throughout the first emulsification process. When the resulting emulsion is poured into a aqueous phase without ethyl acetate, the ethyl acetate begins to diffuse outward and dissolve in the aqueous phase, resulting in the solidification of the oil droplets. The picture shows the SEM photos of ethyl cellulose powder with different mass ratio of ethyl cellulose to ethyl acetate. As can be seen from the figure, the ethylcellulose powder obtained after emulsion treatment shows a relatively regular structure. Similarly, it can be seen from the figure that during the preparation process, the content of ethyl cellulose in the oil phase solution, that is, the mass ratio of ethyl cellulose to ethyl acetate, has a great influence on the microstructure of the obtained powder. When the mass ratio of ethyl cellulose to ethyl acetate is 0.2/10, the structure of the powder tends to be spherical, but the spherical structure is not perfect, and a lot of deformation and inward depression of the surface shell appear. When the ratio rises to 0.4/10, the obtained powder begins to have a more regular spherical structure. However, when the ratio continues to increase to 1.6/10, the morphology of the obtained powder becomes irregular again, and a large number of damaged spherical shell structures appear.
