| Complex fluids are generally produced by mixing together several distinct components. They sometimes possess mixed physical properties of their elements, but in many cases the interaction between different elements can give rise to unusual optical and rheological properties of the system as a whole, reflecting the new structural organization of their elements. The dynamic response of complex fluids when subjected to external perturbations, such as electric and magnetic fields and hydrodynamic flows, is extremely complicated, yet there are some unifying features. As a complex fluid, microemulsion is defined as a mixture of three essential components: two immiscible liquids and surfactant molecules, which is a transparent or semi-transparent thermodynamics steady system. Electrorheological (ER) fluids are a kind of complex fluids that is a suspension of high dielectric constant particles dispersed in an insulating oil of low dielectric constant, which have reversible and adjustable rheological property under the applied electric field. Because of the interaction force of permanent moment, polarized moment, surfactant molecules with electric field, droplets of microemulsion are deform and/or align along the electric field. Thus rotational symmetry of the microemulsion is broken and microemulsion becomes optical anisotropy. An understanding of the physical origins of such phenomena is of great practical and fundamental interest.The optical activity of electrorheological (ER) fluids and microemulsion induced by electric field was systematically investigated in this dissertation. A physical model of electrically induced optical activity of electrorheological fluids is derived. A set of electrorheological fluids and microemulsion with different concentration are prepared and their electrically induced optical activity are measured by means of an automatic polarimeter. On this foundation, the following results have been completed.1. A physical model of electrically induced optical activity of electrorheological fluids is derived. The optical activity resulting from the anisotropic attenuation of different linearly polarized light is considered, and the attenuation of linearly polarized light lies in the light reflection on the interface and the absorption in the ER fluids. According to the theory of light transmission, we derived the expressionof rotation angle ψ as a function of the dielectric constant ε conductivity σ ofER fluid, and θ (the angle between the electric vector of linearly polarized light and electric field) from Maxwell's equations and Fresnel reflection, on the condition of several appropriate approximations and assumptions.2. It has been shown that optical activity can occur in electrorheological fluids under external electric field and optical rotation angle can also be tuned by the electric field. Several kinds of ER fluids with different concentration are prepared and their optical activity are measured with the changes of applied electric field and θ using a automatic polarimeter. Experiments indicate that when none of the external electric field E, concentration C and 9 are equal to zero, ER fluids appear opticalactivity. For a given concentration, optical rotation angle ψ increases with electric field and concentration. It's discovered that optical rotation angle θ increases first,passes through a maximum at 9 - θ0 and then decreases monotonically as θ increases for a given electric field and concentration.3. It has been shown that optical activity can occur in microemulsion under external electric field and optical activity can also be tuned by the electric field. A set of microemulsions of water/Span80/transformer oil with different water content are prepared and their optical activity are measured with the changes of applied electric field and θ , the angle between the electric vector of the incident linearly polarized light and the external electric field, using an automatic polarimeter. Experiments indicate that when none of the external electric... |
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