Pimenta Paloma, Pashkovski Eugene E
Department of Chemical and Biochemical Engineering, Rutgers University, 98 Brett Road, Piscataway New Jersey 08854, USA.
Langmuir. 2006 Apr 25;22(9):3980-7. doi: 10.1021/la0519453.
The linear and nonlinear rheology of viscoelastic mixed anionic-zwitterionic surfactant solutions has been systematically investigated. In the linear viscoelastic regime, these systems display nearly Maxwellian behavior with a unique relaxation time, tau0, and a characteristic elastic plateau modulus, G0. Linear rheological data were used to calculate the repitation and breaking times of the micelles, tau(rep) and tau(b), respectively. Surprisingly, the elastic modulus G0 significantly increases with salt concentration c(s), whereas tau(b) decreases by 1 order of magnitude. The strong effect of c(s) on the material parameters and microstructure of rodlike micelles allowed for the systematic investigation of the effect of these parameters on nonlinear flow. For samples with relatively long tau(b), the quasi-static flow diagram (stress vs shear rate) shows a stress peak followed by a metastable branch (a region of decreasing shear stress), whereas for samples with relatively short tau(b), this phenomenon is not observed. Transient flow responses corroborate quasi-static flow findings and further reveal the significance of microscopic dynamic parameters on flow behavior. Shear stress time series were recorded at constant shear rates, and above a critical shear rate, gamma(c2), stress fluctuations are observed. The amplitude of these stress fluctuations, Delta sigma, was found to scale as Delta sigma approximately equal to G0(tau(b)| gamma - gamma(c2)|)beta with beta approximately 0.5. This scaling is observed for micellar systems with tau(b) ranging from 0.12 to 0.01 s and G0 ranging from 1 x 10(3) to 7 x 10(3) dyn/cm2.
对粘弹性混合阴离子 - 两性离子表面活性剂溶液的线性和非线性流变学进行了系统研究。在线性粘弹性区域，这些体系表现出近乎麦克斯韦行为，具有独特的弛豫时间τ₀和特征弹性平台模量G₀。利用线性流变学数据分别计算了胶束的重复和破裂时间τ(rep)和τ(b)。令人惊讶的是，弹性模量G₀随盐浓度c(s)显著增加，而τ(b)减小了1个数量级。c(s)对棒状胶束的材料参数和微观结构的强烈影响使得能够系统地研究这些参数对非线性流动的影响。对于τ(b)相对较长的样品，准静态流动图（应力与剪切速率）显示出一个应力峰值，随后是一个亚稳分支（剪切应力降低的区域），而对于τ(b)相对较短的样品，未观察到这种现象。瞬态流动响应证实了准静态流动的结果，并进一步揭示了微观动态参数对流动行为的重要性。在恒定剪切速率下记录剪切应力时间序列，并且在高于临界剪切速率γ(c2)时，观察到应力波动。发现这些应力波动的幅度Δσ按Δσ≈G₀(τ(b)|γ - γ(c2)|)β缩放，其中β≈0.5。对于τ(b)范围从0.12到0.01 s且G₀范围从1×10³到7×10³ dyn/cm²的胶束体系观察到这种缩放关系。
