IR Studies of Interfacial Interaction of the Succinic Surfactants with Different Head Groups in Highly Concentrated W/O Emulsions

Abstract

The interfacial properties of three succinic surfactants (PIBSA) with different hydrophilic end groups and sorbitan monooleate (SMO) in water-in-oil emulsions of the liquid explosive type were studied. The aqueous phase contained 40% of ammonium nitrate (AN). The trend in equilibrium interfacial tension was found to be PIBSA-MEA > PIBSA-UREA > PIBSA-MEA/SMO mixture > PIBSA-IMIDE > SMO, where MEA, UREA, IMIDE are amid/amide, urethane and imide end groups, respectively. The same trend was observed for the interfacial elastic modulus. The FTIR study revealed interactions between surfactant head groups and an AN solution. The interactions depend on the polarity of head groups determined by their chemical structure. The packing efficiency of the surfactants under study is also influenced by the chemical structure of head groups. Attempts to model the conformation of the surfactants at the interface were made. The investigation of mixed interfacial cover (PIBSA-MEA/SMO) showed that SMO remained at the interface reducing the interfacial tension at the W/O interface. It was also demonstrated that variation of the nature of head groups influences the rheological properties of emulsions. Bulk elasticity and yielding correlate with interfacial interaction characteristics.

Keywords:

• Bulk rheology
• FTIR study
• interfacial elasticity
• interfacial tension
• succinic surfactants
• surfactant blend
• water-in-oil emulsions

Acknowledgements

The authors thank Lake International Technologies and African Explosives Limited for their financial support, for providing the objects for investigation, and for permission to publish the results.

Notes

*The result was reported elsewhere.^{[ 7 ]}

**The result was reported elsewhere.^{[ 12 ]}

*The G⁰ values correspond to the plateau region of the modulus vs. amplitude of deformations dependence at low strain amplitudes.