Freiberger Norbert, Moitzi Christian, de Campo Liliana, Glatter Otto
Institute of Chemistry, University of Graz, Heinrichstrasse 28, A-8010 Graz, Austria.
J Colloid Interface Sci. 2007 Aug 1;312(1):59-67. doi: 10.1016/j.jcis.2006.06.033. Epub 2006 Jun 27.
SANS is a powerful tool to characterise microemulsions, which can have a discontinuous droplet-like structure (oil in water (O/W), water in oil (W/O)) or a bicontinuous one. In the present study, we try to distinguish O/W, W/O and bicontinuous microemulsions by SANS measurements under practical conditions and by a certain evaluation technique. For this reason we chose the well characterised ternary system water-non-ionic surfactant (C(12)E(5))-oil (n-octane), at a fixed surfactant concentration and performed SANS measurements throughout its one-phase channel where droplet-like phases as well as bicontinuous phases are well established. We evaluated the scattering data via the 'Generalised Indirect Fourier Transformation' method (GIFT) which is based on a particulate picture. It should therefore give good results in the droplet domains while a poor fit could be expected for the bicontinuous regime. For comparison we also applied the model of Teubner and Strey (TS) which was developed especially for bicontinuous phases, here a bad fit can be expected for the particulate regime. The data evaluation via GIFT leads to relatively good fits throughout the one-phase channel. The results are physically meaningful and are comparable to those of the TS model. We show that the scattering pattern of a bicontinuous microemulsion can be represented by that of a polydisperse particulate system. This is in clear contradiction to the expectation that the particle picture used in the GIFT method must fail when the bicontinuous regime is reached.
小角中子散射（SANS）是表征微乳液的有力工具，微乳液可以具有不连续的液滴状结构（水包油（O/W）、油包水（W/O））或双连续结构。在本研究中，我们试图在实际条件下通过SANS测量并采用一定的评估技术来区分O/W、W/O和双连续微乳液。因此，我们选择了特征明确的三元体系水-非离子表面活性剂（C(12)E(5)）-油（正辛烷），在固定的表面活性剂浓度下，在其单相区进行SANS测量，在该区液滴状相和双连续相都已充分形成。我们通过基于颗粒图像的“广义间接傅里叶变换”方法（GIFT）评估散射数据。因此，在液滴区域应能得到良好的结果，而对于双连续区域，预计拟合效果较差。为了进行比较，我们还应用了Teubner和Strey（TS）模型，该模型是专门为双连续相开发的，在这里，对于颗粒区域预计拟合效果较差。通过GIFT进行的数据评估在整个单相区都能得到相对较好的拟合。结果具有物理意义，并且与TS模型的结果具有可比性。我们表明，双连续微乳液的散射图案可以用多分散颗粒体系的散射图案来表示。这与预期明显矛盾，即当达到双连续区域时，GIFT方法中使用的颗粒图像必然失效预期。
