Comparative Study of Conventional/Ethoxylated/Extended n‑Alkylsulfate Surfactants

• Published in: Langmuir 2019-02, Vol.35 (8), p.3116-3125
• Main Authors: Chen, Ji, Hu, Xue-yi, Fang, Yun, Liu, Huan-huan, Xia, Yong-mei
• Format: Article
• Language: English
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/acs.langmuir.8b04022

A series of novel anionic e-surfactants n-C c P p S was molecular designed and synthesized from long-chain fatty alcohols by polypropoxylation and sulfation followed by neutralization. Excellent all-round performance of extended surfactants (e-surfactants) interests us how a simple polypropylene oxide (PPO) spacer has great effects on properties. By a comparative study of conventional/ethoxylated/extended n-alkylsulfate surfactants, we were surprised to find that e-surfactants are in an obvious rugby shape at the air/water surface according to molecular surface area (a m), and it comes down to the intramolecular PPO spacer coiling and surface-induced collapse. On the basis of the interfacial properties of the e-surfactants, it is found that the PPO spacer can provide both hydrophilic and lipophilic contributions to an e-surfactant molecule. The synergism between PPO spacers and alkyl chains indicates that a certain PPO spacer can adjust the contributions in view of different alkyl chain lengths. Therefore, it is both the rugby-shaped molecular geometry of e-surfactants and the dynamic amphipathicity of a PPO spacer that makes e-surfactants behave with excellent interfacial and solution properties for household cleaning. Therefore, this work gives us a hint that the molecular geometry of surfactants plays a vital role in interfacial and solution properties similar to molecular amphipathicity.