高亲水性纳米二氧化硅颗粒稳定范德华乳液

Van der Waals emulsions stabilized solely by hydrophilic nano-silica particles

利用未修饰的高亲水性纳米二氧化硅颗粒(SiO_(2)NPs)在其等电点附近制备了范德华乳液。结果表明,在等电点(pH 2.7)下,SiO_(2)NPs借助高速均质与油/水界面剧烈混合,并受范德华引力的驱动逼近界面,在SiO_(2)NPs质量分数0.5%、水相体积分数50%的条件下稳定为平均粒径244μm的O/W型范德华乳液。增加SiO_(2)NPs的质量分数或减小油相体积分数可提高单位油滴界面附近的颗粒数,增大连续相黏度并促进乳液液滴之间形成三维网络结构,从而提高乳液稳定性。通过调节连续相的pH以促进SiO_(2)NPs表面的羟基发生质子化与去质子化的转变,可实现乳液3次pH响应乳化-破乳循环。

Van der Waals emulsion was prepared by unmodified and highly hydrophilic nano-silica particles(SiO_(2)NPs)near their isoelectric point.The results showed that SiO_(2)NPs suspension was strongly mixed with oil by high speed homogenization,van der Waals forces between SiO_(2)NPs and oil droplets were sufficient to trap SiO_(2)NPs in close proximity to the oil/water interface when p H of SiO_(2)NPs suspensions was equal to the isoelectric point(2.7),and the O/W van der Waals emulsion with an average size of emulsion droplets of 244μm was obtained under the conditions of SiO_(2)NPs mass fraction of 0.5% and water phase volume fraction of 50%.Increasing mass fraction of SiO_(2)NPs or decreasing oil phase volume fraction could increase the number of particles near the unit oil droplet interface,increase the viscosity of continuous phase and promote the formation of three-dimensional network structure between emulsion droplets,thus improving the stability of the emulsion.Adjusting the pH of the continuous phase to promote the protonation and deprotonation of the hydroxyl groups on the surface of SiO_(2)NPs,the emulsion could achieve three pH response emulsification and demulsification cycles.