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通过小角中子散射获得的水包二氧化碳微乳液中表面活性剂膜的性质。

Properties of surfactant films in water-in-CO2 microemulsions obtained by small-angle neutron scattering.

作者信息

Yan Ci, Sagisaka Masanobu, James Craig, Rogers Sarah, Alexander Shirin, Eastoe Julian

机构信息

School of Chemistry, University of Bristol, Bristol BS8 1TS, United Kingdom.

Department of Materials Science and Technology, Faculty of Science and Technology, Hirosaki University, Bunkyo-cho 3, Hirosaki, Aomori 036-8561, Japan.

出版信息

J Colloid Interface Sci. 2014 Dec 1;435:112-8. doi: 10.1016/j.jcis.2014.08.040. Epub 2014 Sep 1.

Abstract

HYPOTHESIS

The formation, stability and structural properties of normal liquid phase microemulsions, stabilized by hydrocarbon surfactants, comprising water and hydrocarbon oils can be interpreted in terms of the film bending rigidity (energy) model. Here, this model is tested for unusual water-in-CO2 (w/c) microemulsions, formed at high pressure with supercritical CO2 (sc-CO2) as a solvent and fluorinated surfactants as stabilizers. Hence, it is possible to explore the generality of this model for other types of microemulsions.

EXPERIMENTS

High Pressure Small-Angle Neutron Scattering (HP-SANS) has been used to study w/c microemulsions, using contrast variation to highlight scattering from the stabilizing fluorinated surfactant films: these data show clear evidence for spherical core-shell structures for the microemulsion droplets.

FINDINGS

The results extend understanding of w/c microemulsions since previous SANS studies are based only on scattering from water core droplets. Here, detailed structural parameters for the surfactant films, such as thickness and film bending energy, have been extracted from the core-shell SANS profiles revealed by controlled contrast variation. Furthermore, at reduced CO2 densities (∼0.7gcm(-3)), elongated cylindrical droplet structures have been observed, which are uncommon for CO2 microemulsions/emulsions. The implications of the presence of cylindrical micelles and droplets for applications of CO2, and viscosity enhancements are discussed.

摘要

假设

由烃类表面活性剂稳定、包含水和烃油的正常液相微乳液的形成、稳定性和结构特性,可以根据膜弯曲刚度(能量)模型来解释。在此,该模型针对在高压下以超临界二氧化碳(sc-CO2)作为溶剂、氟化表面活性剂作为稳定剂形成的非常规水包二氧化碳(w/c)微乳液进行了测试。因此,有可能探索该模型对其他类型微乳液的通用性。

实验

高压小角中子散射(HP-SANS)已被用于研究w/c微乳液,利用对比变化来突出稳定的氟化表面活性剂膜的散射:这些数据清楚地证明了微乳液滴具有球形核壳结构。

发现

这些结果扩展了对w/c微乳液的理解,因为之前的小角中子散射研究仅基于水核液滴的散射。在此,已从通过控制对比变化揭示的核壳小角中子散射轮廓中提取了表面活性剂膜的详细结构参数,如厚度和膜弯曲能。此外,在降低的二氧化碳密度(约0.7g/cm³)下观察到了细长的圆柱形液滴结构,这在二氧化碳微乳液/乳液中并不常见。讨论了圆柱形胶束和液滴的存在对二氧化碳应用和粘度增强的影响。

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