扩散波谱技术研究离子液体微乳液[Bmim]BF4/Tween-20/二甲苯的流变性

Study on rheological properties of ionic liquid microemulsion [Bmim]BF4/Tween-20/Xylene by diffusing-wave spectroscopy

为研究离子液体微乳液体系[Bmim]BF4/Tween-20/二甲苯的流变性,采用DWS技术,以TiO2为示踪粒子,通过测定自相关函数(g2-1)与弛豫时间的关系,得到了示踪粒子的均方位移(<Δr2>)以及微乳液体系的储能模量G′、损耗模量G″和复合模量G*,同时结合旋转粘度计测量结果对微乳液流变行为进行了探讨。DWS结果表明:示踪粒子均方位移<Δr2>与弛豫时间τ具有线性关系,随着二甲苯质量百分数的增加,均方位移增大,二者幂律关系为<Δr2>~τ0.87~0.91,表明示踪粒子在微乳液体系中具有亚扩散行为;微乳液体系的G″>>G′,G″与角频率ω的幂律关系为G″~ω0.86~0.93。旋转粘度计结果表明:微乳液体系具有轻微的剪切变稀行为。DWS和旋转粘度计测定结果均表明离子液体微乳液为黏性近牛顿流体。

In order to study the rheological properties of ionic liquid microemulsion system[Bmim] BF 4/Tween-20/xylene,the relationship between autocorrelation function ( g 2-1) and relaxation time was determined using DWS technique with TiO 2 as tracer particles. The mean square displacement of tracer particles (<Δr 2>),the storage modulus G ′,the loss modulus G ″ and the composite modulus G * of the microemulsion system were obtained. Meanwhile,the rheological behavior of microemulsion was discussed by combining with the measured results of rotational viscometer. Results of DWS measurement showed that the mean square displacement<Δr 2>had a linear relationship with the relaxation time τ,with the increase of the mass percentage of xylene,the value of <Δr 2> increased,and the power law relation between them was <Δr 2>~τ 0.87~0.91 ,indicating that tracer particles had sub-diffuse behavior in the microemulsion system. It was also observed that G ″>> G ′,the power law relation between G ″ and angular frequency ω was G″~ω 0.86~0.93 . The results of rotational viscometer measurement revealed that the microemulsion system had a slight shear thinning behaviour. Both the DWS and rotational viscometer measurement showed that the ionic liquid microemulsion belonged to viscous near Newtonian fluid.