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OTAC/NaSal虫状胶束流体微观结构与线性黏弹性

THE MICROSTURCTURE AND LINEAR VISCOELASTICITY OF OTAC/NASAL WORMLIKE MICELLES

  • 摘要: 采用流变学、冷冻蚀刻电镜方法,研究了十八烷基三甲基氯化铵(octadecyl trimetryl ammoiumchloride,OTAC)阳离子表面活性剂和水杨酸钠(NaSal)体系蠕虫状胶束的形成、线性黏弹性与微观胶束结构。研究结果表明,在OTAC主溶液与NaSal质量比为5:1时,体系形成了最大长度达1um左右的蠕虫状胶束。当OTAC主溶液质量浓度为1.4%时,以线性虫状胶束为主;当浓度大于2.8%时,胶束开始相互缠结,形成网状结构;当浓度达到4%时,胶束缠结长度le值达到一个极小值,松弛时间也达到最大值2.86s,说明此时体系形成了致密的网状结构,并呈现良好的黏弹性。在较低振荡频率时,缠结的虫状胶束符合Maxwell流体特征,但在较高频率区域,OTAC/NaSal蠕虫状胶束表现出了不同于一般聚合物的应力释放机制,随着网状结构的增强,其应力释放机制呈现虫状胶束所特有的“Rouse-like”和“breathing”效应。

     

    Abstract: The formation, microstructure and linear viscoelasticity of wormlike micelles with octadecyl trimetryl ammoium chloride (OTAC)/sodium salicylate (NaSal) were analyzed with the method of rheology and freeze-fracture transmission electron microscopy (FF-TEM). It is shown that the long wormlike micelles with several micrometers are obtained if the mass ratio of the OTAC master solution to NaSal is 5:1. The linear micelle is dominated when the OTAC master solution weight content is 1.4%. The micelles begin to entangle with the increase of the OTAC solution concentration. When the weight content of OTAC master solution is 4% at a constant mass ratio, 5:1 of OTAC to NaSal, the minimum of entanglement length, le, may occur and the solution shows good viscoelasticity with a longer relaxtion time, 2.86 second. The entanglement wormlike micelles show the Maxwellian behavior at low frequency and the deviation occurs at high oscillation frequency. The deviation shows that the "breathing" and "Rouse-like" motions of wormlike micelles will dominate the stress relaxation process for the entanglements of micelles. It is a solely characteristic stress relaxation mechanism of wormlike micelles at high oscillation frequency.

     

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