Acta Phys. -Chim. Sin. ›› 2014, Vol. 30 ›› Issue (6): 1142-1147.doi: 10.3866/PKU.WHXB201404011

• SOFT MATTER • Previous Articles     Next Articles

Salt Effects on the Network-Like Aggregates of Gemini Surfactant Studied by Dynamic Light Scattering

LIU Fen, XIE Dan-Hua, ZHAO Jian-Xi   

  1. Institute of Colloid and Interface Chemistry, College of Chemistry and Chemical Engineering, Fuzhou University, Fuzhou 350108, P. R. China
  • Received:2014-01-21 Revised:2014-03-31 Published:2014-05-26
  • Contact: ZHAO Jian-Xi E-mail:jxzhao.colloid@fzu.edu.cn
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (20873024, 21273040).

Abstract:

The effects of different salts on the self-assembly of the carboxylate Gemini surfactant O,O'-bis (sodium 2-dodecylcarboxylate)-p-dibenzenediol (referred to as C12φ2C12) were studied using dynamic light scattering measurements. The results showed that the addition of salts induced the transition of the networklike aggregates into two new aggregates with small (hydrodynamic radii Rh,app of several nanometers) and large (Rh,app>100 nm) sizes, which coexisted in solution. A solubilization test using a 1,6-diphenyl-1,3,5-hexatriene (DPH) probe confirmed that the small aggregates were spherical micelles with a core-shell structure. Rheological measurements suggested that the large aggregates were threadlike micelles. The aggregate transition was attributed to the instability of the initially formed network-like aggregates. The added counter-ions associated with the head-groups of C12φ2C12, which destroyed the hydrophile-lipophile balance and resulted in the aggregate transition. The salt effect followed the order: MgCl2>NaCl, Bu4NBr>Me4NBr>Et4NBr>Pr4NBr, where Bu4NBr is special and not in the order of electrostatic attraction since it provides an additional force through the hydrophobic interaction of its butyls with the alkyl tails of C12φ2C12.

Key words: Gemini surfactant, Long rigid spacer, Network-like aggregate, Aggregate transition, Salt effect

MSC2000: 

  • O648