Li Guofeng, Yi Xiangyi, Jiang Jitao, Zhang Yu, Li Yueli
State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation (Chengdu University of Technology), Chengdu, Sichuan Province 610059, China; College of Energy, Chengdu University of Technology, Chengdu, Sichuan Province 610059, China; Petro-Engineering Research Institute of North China Oil and Gas Branch, Sinopec, Zhengzhou, Henan Province 450006, China.
State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation (Chengdu University of Technology), Chengdu, Sichuan Province 610059, China; College of Energy, Chengdu University of Technology, Chengdu, Sichuan Province 610059, China; Petro-Engineering Research Institute of North China Oil and Gas Branch, Sinopec, Zhengzhou, Henan Province 450006, China.
Colloids Surf B Biointerfaces. 2020 Nov;195:111248. doi: 10.1016/j.colsurfb.2020.111248. Epub 2020 Jul 7.
This study analyzes the equilibrium and dynamic surface tension curves of acidic and lactonic sophorolipids (SLs). It also investigates the dilational properties of the surface adsorptive film. Given their high hydrophobicity, lactonic SLs have lower surface tension and critical micelle concentration (CMC) than acidic SLs. As c increases, the CMC values and the corresponding surface tension (γ) of acidic and lactonic SLs decrease gradually. For dynamic surface properties, lactonic SLs have a high diffusive rate from the bulk phase to the subsurface. At 0.05 CMC, the initial adsorption of acidic and lactonic SLs is diffusion-controlled. As c increases, the values of diffusion coefficient (D) show a downward trend, and the mechanism is mixed kinetic diffusion. Adding NaCl increases the D values of acidic and lactonic SLs, and the influence degree for acidic SLs is more considerable than that for lactonic SLs. As frequency (ω) increases (0.005∼0.5 Hz), the dilational elasticity increases, and the phase angle decrease. The dilational elasticity of acidic and lactonic SLs shows a low-frequency dependence. Compared with acidic SLs, lactonic SLs have better dynamic surface properties, which decrease the gradient of interfacial tension because of the interface deformation. Consequently, the lactonic SLs exhibit a relatively small dilational elasticity. At 0.1 Hz, the dilational elasticity of acidic and lactonic SLs reaches the maximum values at 0.05CMC and 0.075CMC, respectively. When c rises near CMC, the phase angle increases obviously, and the dilational elasticity further decreases. This result is attributed to the fast exchange of surfactant molecules between the interface and the micelles.
本研究分析了酸性和内酯型槐糖脂（SLs）的平衡和动态表面张力曲线。还研究了表面吸附膜的扩张性质。由于内酯型SLs具有较高的疏水性，其表面张力和临界胶束浓度（CMC）低于酸性SLs。随着c增加，酸性和内酯型SLs的CMC值和相应的表面张力（γ）逐渐降低。对于动态表面性质，内酯型SLs从本体相到亚表面具有较高的扩散速率。在0.05 CMC时，酸性和内酯型SLs的初始吸附是扩散控制的。随着c增加，扩散系数（D）值呈下降趋势，其机制为混合动力学扩散。添加NaCl会增加酸性和内酯型SLs的D值，且对酸性SLs的影响程度比对内酯型SLs更显著。随着频率（ω）增加（0.005∼0.5 Hz），扩张弹性增加，相角减小。酸性和内酯型SLs的扩张弹性表现出低频依赖性。与酸性SLs相比，内酯型SLs具有更好的动态表面性质，由于界面变形，其降低了界面张力梯度。因此，内酯型SLs表现出相对较小的扩张弹性。在0.1 Hz时，酸性和内酯型SLs的扩张弹性分别在0.05CMC和0.075CMC时达到最大值。当c在CMC附近升高时，相角明显增加，扩张弹性进一步降低。该结果归因于表面活性剂分子在界面和胶束之间的快速交换。
