Formation of Particle Coated Fusiform Droplets via Lowering Interface Tension with Polyaluminum Sulfate

Abstract

It was found that the interface tension between water and alkenyl succinic anhydride (ASA) was significantly reduced by polyaluminum sulfate (PAS), increased considerably though by TiO₂ nanoparticle. PAS with basicity of 0.75 (PAS-0.75) reduced the interface tension to a larger extent than PAS with basicity of 0.3 (PAS-0.3). By reducing interface tension with PAS-0.75, ASA-in-water emulsion bearing fusiform geometries was constructed. The emulsion stabilized by PAS-0.3 and TiO₂ nanoparticle bore spherical shapes with the exception when mass fraction of TiO₂ nanoparticle was low, in which case fused nonspherical drops were formed. Forming nonspherical emulsion crucially depends on ASA-water interface tension, where a critical interface tension was identified to be 0.6–0.7 mN/m. The fusiform geometries were transformed into spherical shapes when interface tension was higher than 0.7 mN/m. Both the lowering mechanism of the interface tension and the formation mechanism of the fusiform emulsion were proposed.

Keywords:

• Alkenyl succinic anhydride (ASA)
• fusiform droplets
• interface tension
• particle stabilized emulsion
• polyaluminum sulfate
• TiO₂ nanoparticle

Acknowledgments

This work is financially supported by National Natural Science Foundation of China (20976099), Shandong Natural Science Foundation (ZR2010CM008). The authors are grateful to Mr. Zhenhuan Zhao for his help in DLS analysis.