pH对油酸钠/盐酸三乙胺蠕虫状胶束流变性质的影响

Effect of pH on Rheological Properties of Wormlike Micelles Formed by Sodium Oleate/Triethylamine Hydrochloride

摘要:

用流变学方法研究了pH对油酸钠/盐酸三乙胺(NaOA/Et3NHCl)蠕虫状胶束溶液流变性质的影响。通过稳态剪切和动态流变实验发现，30℃时，NaOA(0.12mol稬-1)/ Et3NHCl(0.2mol稬-1)溶液在pH=8.20-9.40之间循环变化时，pH对溶液粘度的改变具有“开关”效应，可实现粘度在3-27649 mPa稴范围内反复变化三次以上。体系在pH=8.55-9.02为蠕虫状胶束，其流变行为符合Maxwell模型。这种溶液流变性对pH的响应行为是由于pH对反离子Et3NH 与NaOA的相互作用影响而产生的。当pH降低时，反离子Et3NH 的离子势增大，导致胶束表面电荷密度降低，蠕虫状胶束进一步增长。当pH=8.64，胶束因相互吸引而析出。而在初始条件下，升高pH=9.40，反离子Et3NH 从胶束中解吸出来，蠕虫状胶束受到破坏。

Abstract:

The rheological behaviors of a pH-switchable wormlike micelles system formed by Sodium Oleate/Triethylamine Hydrochloride were investigated by rheology method. Though steady-state and dynamic rheological measurements, it was found that at 30℃, when the pH value is cycled between 8.20 and 9.40,the viscosity of the NaOA(0.12mol稬-1)/ Et3NHCl(0.2mol稬-1) solutions vares without any deterioration to its response more than three times between 3 and 27649 mPa稴,and also its rheological behavior complies with Maxwell model. These pH-stimuli rheological properties were attributed to the effect of pH on the interaction between NaOA and counterions Et3NH . Upon decreasing pH, the micellar surface charge density was decreased due to lowing of counterions Et3NH ionic strength, leading the micelles grow continuously .while upon decreasing pH to 8.64, flocculation occurs due to the attractive interactions between adjacent micelles. However, on increasing pH to 9.40, the micellar structures were destroyed due to counterions Et3NH desorbing from the surface of the wormlike micelles.