The dynamic interfacial tensions (IFTs) of four extended surfactants (S-C₁₂PO₁₃S, L-C₁₂PO₄S, L-C₁₆PO₄S and L-C₁₂PO₁₁S) with different alkyl chain length and polypropylene oxide (PO) group against hydrocarbons were investigated. The mechanism responsible for the IFT reduction for extended surfactant has been detected. According to experimental results, we found that only when the size of hydrophobic part is enlarged to match the size of anionic head, the ultralow IFT will appear at optimized hydrophilic-lipophilic balance. For extended surfactants, with an increase of PO number, the curled PO chains occupy larger spaces at interface and match the size of anionic head. As a result, the ultralow IFT appears against alkanes when PO number is 13. The increase of alkyl chain length shows little effect on the size of hydrophobic part and ability of reducing IFT. Moreover, with an increase of n-alkane carbon number (ACN), the size of hydrophobic part increases as a function of ACN. Therefore, the increase of size of hydrophobic part compensates the decrease of adsorbed amount when ACN is higher than n_min value (the n-alkanes carbon number when the IFTs reach the minimum), which results in the “L” shape of IFT curve with a function of ACN.

四种扩展表面活性剂（SC ₁₂ PO ₁₃ S、LC ₁₂ PO ₄ S、LC ₁₆ PO ₄ S和LC ₁₂ PO ₁₁）的动态界面张力（IFT）研究了具有不同烷基链长度和聚环氧丙烷 (PO) 基团的 S) 对烃的影响。已检测到延长表面活性剂的 IFT 降低的机制。根据实验结果，我们发现只有当疏水部分的尺寸扩大到与阴离子头的尺寸相匹配时，才会在优化的亲水亲油平衡下出现超低的IFT。对于扩展型表面活性剂，随着 PO 数的增加，卷曲的 PO 链在界面上占据更大的空间并匹配阴离子头的大小。因此，当PO数为13时，对烷烃出现超低的IFT。烷基链长的增加对疏水部分的大小和降低IFT的能力几乎没有影响。此外，随着正烷烃碳数（ACN）的增加，疏水部分的大小随着 ACN 的增加而增加。因此，当 ACN 高于 n 时，疏水部分尺寸的增加补偿了吸附量的减少。_min值（IFT 达到最小值时的正烷烃碳数），这导致 IFT 曲线呈“L”形，随 ACN 变化。