Key Laboratory of Colloid and Interface Chemistry, Shandong University, Ministry of Education, Jinan, P R China.
J Phys Chem B. 2011 Feb 10;115(5):980-9. doi: 10.1021/jp107946n. Epub 2011 Jan 11.
Shear-induced structural transition and recovery were studied by freeze-fracture transmission electron microscopy, cryogenic transmission electron microscopy (cryo-TEM), rheological measurements, and the variation of birefringent textures in the system of tetradecyltrimethylammonium hydroxide (TTAOH)/lauric acid (LA)/deoxycholic acid (DeCA)/H(2)O as a function of the molar fraction of DeCA [x = n(DeCA)/(n(DeCA) + n(LA))]. At x = 0.3, giant vesicles and planar lamellar structures were formed before exerting shearing. Shear thickening and large hysteresis loop are observed under shearing, indicating the occurrence of structural transition. Multilamellar and close-packed vesicles were determined by cryo-TEM observations. Exerting further shearing, the elastic properties of the sample were increased due to the strip off of the outer shell of the vesicles and formation of small vesicles. After shearing was stopped, the sample can slowly relax back to the original state. At x = 0.25, lamellar structures, giant vesicles, and small unilamellar vesicles were observed. Cryo-TEM observations show that the multilamellar vesicles can be formed after exerting shearing, and the sample cannot spontaneously recover to the original state. At x = 0.2, vesicles are dominant in the solution, and the aggregates structures are almost the same before and after shearing. Shearing can increase the elastic properties of the sample, which is ascribed to the strip off of the outer shells of the multilamellar vesicles, forming much smaller vesicles in the solution.
通过冷冻断裂透射电子显微镜、低温透射电子显微镜（cryo-TEM）、流变测量以及十四烷基三甲基氢氧化铵（TTAOH）/月桂酸（LA）/脱氧胆酸（DeCA）/H2O 体系的双折射纹理变化研究了剪切诱导的结构转变和恢复，作为 DeCA 的摩尔分数 [x = n（DeCA）/（n（DeCA）+n（LA））] 的函数。在 x = 0.3 时，在施加剪切之前形成了巨大的囊泡和平面层状结构。在剪切下观察到剪切增稠和大滞后环，表明发生了结构转变。低温透射电子显微镜观察确定了多层膜和紧密堆积的囊泡。进一步施加剪切时，由于囊泡的外壳剥落和小囊泡的形成，样品的弹性性质增加。停止剪切后，样品可以缓慢恢复到原始状态。在 x = 0.25 时，观察到层状结构、巨大的囊泡和小的单室囊泡。低温透射电子显微镜观察表明，施加剪切后可以形成多层囊泡，而样品不能自发恢复到原始状态。在 x = 0.2 时，溶液中囊泡占主导地位，剪切前后的聚集结构几乎相同。剪切可以增加样品的弹性性质，这归因于多层囊泡的外壳剥落，在溶液中形成更小的囊泡。
