Study On The Behavior Of Colloid Particles At Liquid-liquid Interface

The adsorption of solid particles on the oil-water interface can effectively stabilize dispersion systems such as emulsions and foams.Due to their excellent stability,solid particle-stabilized emulsions(Pickering emulsions)have a wide range of applications in cosmetics,drug delivery and catalysis.The interfacial behavior,such as the three-phase contact angle and arrangement of solid particles at the interface,are crucial to the stability of the emulsion.The particles of stable emulsions are mostly nanoparticles,and there is currently no suitable test method to observe the change of the contact angle and arrangement of the particles on the interface.Light curing has the advantage of rapid polymerization.As long as the appropriate light curing components are added to the oil phase,the solid particles can be instantly fixed on the two-phase interface,so that the contact angle and arrangement of the solid particles on the interface can be observed by SEM.Thus,this topic firstly explores the feasibility of this method,and then explores the factors that affect the contact angle and arrangement of particles on the interface.The specific research contents are as follows:(1)First,the light-curing component was selected as the oil phase,and an O/W Pickering emulsion was prepared.The emulsion droplets were instantly cured by light-curing,so that the solid particles adsorbed on the oil-water interface could be quickly and firmly fixed.The effects of solid particle concentration,modification degree of silane coupling agent and particle size on the interface behaviors such as particle interface density,arrangement and three-phase contact angle were systematically explored.The results show that the particle density at the oil-water interface increased gradually with the increase of the particle concentration in the oil phase and tends to be stable.The hydrophobicity of the solid particles was improved,and the contact angle of the particles at the oil-water interface gradually increased from 37° to 116°.With the same degree of hydrophobic modification,the contact angle of solid particles decreased with the increase of particle size,and the influence of line tension on the contact angle was calculated by the Young-Dupré equation.(2)Second,the effect of functional groups on the surface of silica particles on the adsorption and arrangement on the interface was first explored.The study showed that the interaction between the silane coupling agent and the oil phase would affect the adsorption of the particles on the interface.The competitive adsorption on the interface of silica particles with the same modification degree and different particle sizes was studied.When the number of smaller particles is greater than that of larger particles,smaller particles tend to be preferentially adsorbed on the interface and will inhibit the adsorption of larger particles;When the number of the two is the same,the larger particle size is preferentially adsorbed on the interface.The adsorption behavior of rod-shaped silica on the interface was explored.It is preferentially adsorbed on the interface in a "lying" manner.When different shapes of silica are added to the oil phase at the same time,rod-shaped silica is preferentially adsorbed.Combining the three factors of particle size,quantity and shape,it can be found that effectively reducing the interfacial tension is the key factor for the preferential adsorption of particles on the interface.(3)Finally,we focused on the effects of interface properties on the three-phase contact angle and arrangement of particles.The polarity of the oil phase has a great influence on the three-phase contact angle of the particles,and the oil with high polarity corresponds to a smaller contact angle.The influence of the interface curvature on the three-phase contact angle and arrangement of the particles is studied.The change of the curvature does not significantly affect the change of the contact angle,but the increase of the curvature will reduce the arrangement density of the particles on the interface.When the emulsion droplet radius is more than 10 times the particle radius,the particle density at the interface reaches the maximum value and no longer increases significantly.When the emulsion droplet radius is less than 10 times the particle radius,the particle density decreases rapidly at the interface.At the same time,the salt concentration also affects the density of particles at the interface.Emulsification and solidification at low temperature can promote the transformation of some particles from six directions to four directions.