Synthesis and Aqueous Solution Properties of Polyoxyethylene Surfactants with Ultra-Long Unsaturated Hydrophobic Chains

Abstract

Methoxypolyethylene glycols (M _n = 750, 1000, 2000, and 5000 g/mol) were hydrophobically modified by transestification with mono-unsaturated alkyl chains (UC18, UC22, and UC24), and the obtained ultra-long-chain nonionic surfactants were characterized by ¹H NMR, FTIR and gel permeation chromatographic, respectively. Aqueous solution properties of all these surfactants, including cloud point, surface activities, viscosifying ability, and phase diagrams were examined. It was found that all these ultra-long-chain polyoxyethylene surfactants exhibit good water solubility and typical Newtonian rheological behavior. For the surfactants with the same hydrophobic length, the CP, equilibrium surface tension (γ_cmc), as well as zero-shear viscosity (η₀) increase with increasing their hydrophilic length; for those with same hydrophilic head group, the critical micellar concentration and η₀ increase while the γ_CMC decreases with increasing hydrophobic tail length. Moreover, a decrease in the critical overlap concentration and an increase in the critical temperature were observed in phase diagrams of all these ultra-long-chain polyoxyethylene surfactants. (Supplemental materials are available for this article. Go to the publisher's online edition of the Journal of Dispersion Science and Technology to view the free supplemental file.)

Keywords:

• Nonionic surfactants
• phase behavior
• polyoxyethylene surfactants
• surface activity
• ultra-long-chain surfactants

Acknowledgments

The financial supports from Shandong Provincial governmental “Taishan Scholar” project, Natural Science Foundation of China (No. 21173207), Sichuan Provincial Bureau of Science and Technology (No. 2010JQ0029, No. 2012NZ0006), as well as the Key Laboratory for Colloid and Interface Chemistry of the State Education Ministry at Shandong University (No. 200601) are greatly acknowledged.