Acta Phys. -Chim. Sin. ›› 2016, Vol. 32 ›› Issue (8): 2045-2051.doi: 10.3866/PKU.WHXB201605042

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Foams Stabilized by Fumed Silica Particles with a Quaternary Ammonium Gemini Surfactant

Xiao-Xiang SUN,Yu CHEN,Jian-Xi ZHAO*()   

  • Received:2016-03-08 Published:2016-07-29
  • Contact: Jian-Xi ZHAO
  • Supported by:
    the National Natural Science Foundation of China(21273040);the National Natural Science Foundation of China(21473032)


Fumed silica (F-SiO2) particles were hydrophobized in situ in aqueous solutions of alkanediyl-α, ω-bis(dodecyldimethylammoniumbromide) (12-s-12, s=2, 6) gemini surfactants. This process was assessed using zeta potential measurements. The particles were found to transit from their original hydrophilic nature to hydrophobic and then back to hydrophilic with increases in the surfactant concentration (C). The hydrophobic particles could spontaneously adsorb at the air/water interface, resulting in significant stabilization of aqueous foams. The re-hydrophilic particles desorbed from the interface, leaving only surfactant molecules to stabilize the foam. The strong interfacial elasticity of the surface films was reflected in the highly stable foams. The length of the surfactant spacer also affected the adsorption of the gemini surfactant on the F-SiO2 particles, and therefore had an effect on the elasticity of the adsorbed film and the stability of the foam. The 12-2-12 surfactant, having a relatively short spacer, carried less positive charges because of the incomplete dissociation of its counter ions, resulting in less initial adsorption on the F-SiO2 particles compared with the 12-6-12, but eventually formed a denser monomeric layer because of decreased repulsion between the adsorbed molecules. The 12-2-12 exhibited stronger adsorption at the air/water interface; therefore, the synergistic action of the F-SiO2 particles together with the 12-2-12 produced better foam stabilization compared with the 12-6-12.

Key words: Fumed silica particle, Gemini surfactant, Surface modification, Foam stability