Institute of Agricultural Resources and Environment; Key Laboratory of Wastes Matrix Utilization, Ministry of Agriculture; Shandong Provincial Engineering Research Center of Environmental Protection Fertilizers , Shandong Academy of Agricultural Sciences , Jinan 250100 , P. R. China.
State Key Laboratory of Nutrition Resources Integrated Utilization , Linshu 276700 , P. R. China.
J Phys Chem B. 2018 Sep 20;122(37):8706-8711. doi: 10.1021/acs.jpcb.8b04646. Epub 2018 Sep 5.
Vesicles in surfactant systems are influenced by a shear field. The high shear flow generated by a homogenizer is expected to affect the size of vesicles. Hence, it should be possible to control the size and dispersion of vesicles by tuning the shear. In this study, the influence of shear on the vesicle phase was studied by measuring the rheology and conductivity of a solution made of the nonionic surfactant trideceth-5, a polyethylene glycol ether of tridecyl alcohol with an average number of ethylene oxide of 5, and the anionic surfactant sodium dodecylsulfate. It was found that when shear was applied by a homogenizer, the bilayers of the multilamellar vesicles were stripped off and became unilamellar vesicles, which decreased the viscoelasticity of the system. However, because of the pressure provided by the homogenizer, the newly formed unilamellar vesicles were small and the relative distance between them was large. As a result, the vesicles were no longer crowded and could easily pass each other under shear. This is why the unilamellar vesicles generated by the homogenizer had low viscoelasticity and flow birefringence. Additionally, it took a long time for the unilamellar vesicles to relax back to the original state.
在表面活性剂体系中，囊泡会受到剪切场的影响。匀浆器产生的高剪切流预计会影响囊泡的大小。因此，通过调节剪切，可以控制囊泡的大小和分散性。在这项研究中，通过测量由非离子表面活性剂十三烷醇聚氧乙烯醚 5（一种平均聚合度为 5 的十三醇聚氧乙烯醚）和阴离子表面活性剂十二烷基硫酸钠组成的溶液的流变学和电导率，研究了剪切对囊泡相的影响。结果发现，当通过匀浆器施加剪切时，多层囊泡的双层被剥离并变成单层囊泡，从而降低了体系的粘弹性。然而，由于匀浆器提供的压力，新形成的单层囊泡较小，它们之间的相对距离较大。结果，囊泡不再拥挤，在剪切下可以轻松通过彼此。这就是为什么匀浆器产生的单层囊泡具有低粘弹性和低流动双折射的原因。此外，单层囊泡需要很长时间才能恢复到原来的状态。
