Hashizaki Kaname, Tamaki Nao, Taguchi Hiroyuki, Saito Yoshihiro, Tsuchiya Koji, Sakai Hideki, Abe Masahiko
College of Pharmacy, Nihon University, Funabashi, Chiba, Japan.
Chem Pharm Bull (Tokyo). 2008 Dec;56(12):1682-6. doi: 10.1248/cpb.56.1682.
In the present study, we examine a worm-like micelle consisting of a nonionic surfactant system of polyoxyethylene phytosterol (PhyEO(m))/glycerin fatty acid monoester (GFA-C(n))/Water (m=10, 20, 30; n=8, 10, 12) using rheological measurements looking towards potential application of the system as a gel base. Phase diagrams in the dilute region of the PhyEO(m)/GFA-C(n)/Water systems show the formation of worm-like micelles in some of the surfactant combinations. It is thought that the worm-like micelles form with the GFA-C(n) solubilized in the palisade layer of a spherical or rod-like micelle consisting of PhyEO(m), resulting in a decrease in the interfacial curvature of the molecular assembly. The rheological properties of micellar solutions were examined while changing the ratio of GFA-C(n) (R) with the total concentration of the surfactants (wt%) fixed. Steady-flow viscosity measurements in the region of worm-like micelle formation showed Newtonian flow in the low shear rate region and non-Newtonian flow at higher shear rates. This result shows that the network structure of worm-like micelles does not break in the low shear rate region, but does break in the high shear rate region. The zero-shear viscosity (eta(0)) was calculated from the steady-flow viscosity curve and was found to change dramatically with changing R value, increasing to a value 10000 times that of other values at the maximum. Thus, there is an optimal composition of surfactants which leads to the greatest entanglement of the worm-like micelles. To consider the change in eta(0) in detail, dynamic viscoelasticity measurements were carried out. Consequently, the viscoelastic behavior of the worm-like micelles was found to be similar to the Maxwell model, which represents the most basic model for a viscoelastic body, and it was shown that this worm-like micelle had a single relaxation time. Moreover, it was found that the change in eta(0) of a worm-like micelle was influenced by its mechanical strength.
在本研究中，我们使用流变学测量方法研究了一种蠕虫状胶束，该胶束由聚氧乙烯植物甾醇（PhyEO(m)）/甘油脂肪酸单酯（GFA-C(n)）/水（m = 10、20、30；n = 8、10、12）的非离子表面活性剂体系组成，旨在探索该体系作为凝胶基质的潜在应用。PhyEO(m)/GFA-C(n)/水体系稀溶液区域的相图表明，在某些表面活性剂组合中会形成蠕虫状胶束。据认为，蠕虫状胶束是由于GFA-C(n)溶解在由PhyEO(m)组成的球形或棒状胶束的栅栏层中而形成的，这导致分子聚集体的界面曲率降低。在固定表面活性剂总浓度（wt%）的情况下，改变GFA-C(n)的比例（R），研究了胶束溶液的流变性质。在蠕虫状胶束形成区域进行的稳态流动粘度测量表明，在低剪切速率区域呈现牛顿流动，而在较高剪切速率下呈现非牛顿流动。这一结果表明，蠕虫状胶束的网络结构在低剪切速率区域不会破坏，但在高剪切速率区域会破坏。根据稳态流动粘度曲线计算出零剪切粘度（η(0)），发现其随R值的变化而显著变化，在最大值时增加到其他值的10000倍。因此，存在一种最佳的表面活性剂组成，可导致蠕虫状胶束的最大缠结。为了详细考虑η(0)的变化，进行了动态粘弹性测量。结果发现，蠕虫状胶束的粘弹性行为类似于麦克斯韦模型，该模型代表了粘弹性体的最基本模型，并且表明这种蠕虫状胶束具有单一的弛豫时间。此外，还发现蠕虫状胶束的η(0)变化受其机械强度的影响。
