疏水链长对聚氧乙烯失水山梨醇脂肪酸酯界面扩张流变性质的影响

利用悬挂滴方法研究了系列聚氧乙烯失水山梨醇脂肪酸酯(TweenX)在正癸烷-水界面的扩张流变性质. 实验结果表明, 疏水烷基链长较短的Tween20 分子在界面上吸附量较大, 分子排列更紧密, Tween40 和Tween60具有大致相同的“有效截面积”, 导致饱和吸附时界面张力(γ_cmc)比较接近. TweenX浓度大于临界胶束浓度(cmc)时, 由于Tween20 分子排列的更加紧密, 模量和弹性大于Tween40 和Tween60. 当TweenX的疏水烷基链长达到一定长度时, TweenX的界面膜性质受疏水链长的影响减弱, Tween40和Tween60的扩张参数相差不大.

Effect of Hydrophobic Chain Length on the Interfacial Dilational Rheological Properties of Polyoxyethylene Sorbitan Fatty Acid Ester

The dilational rheological properties of a series of polyoxyethylene sorbitan fatty acid surfactants (TweenX) at the decane/water interface have been investigated using the drop shape analysis method. The experiment results showed that larger quantities of the Tween20 molecules with shorter hydrophobic chain lengths were adsorbed at the interface because they could arrange more closely. Tween40 and Tween60 molecules had similar“actual cross-sectional areas”, which meant that their interfacial tensions were also similar at the critical micelle concentration (γ_cmc). Furthermore, when the bulk concentration exceeded the critical micelle concentration (cmc), the modulus and elasticity of Tween20 were larger than those of Tween40 and Tween60. When the hydrophobic alkyl chain of TweenX reached a certain length, the interfacial film properties of TweenX affected by the hydrophobic chain length decreased, which led to similar dilational parameters.