(162h) High-Pressure Contact Angle Goniometry and Pendant Drop Tensiometry for the Design of Surfactants for the Co2-Water Interface

Compressed CO2 is considered to be a viable alternative to toxic volatile organic solvents. The interest in CO2 stems from the fact that it is inexpensive, and is not regulated by the EPA or FDA. However, owing to a zero dipole moment and weak van der Waals forces, CO2 is a poor solvent for both polar and high molecular weight solutes, characteristics that restrict the applicability of CO2-based processes. To overcome this inability, aqueous dispersions in CO2 have been suggested. Surfactants are employed to form and stabilize emulsions and microemulsions of water and CO2, which find applications in areas including dry cleaning, nanoparticle synthesis, and enzymatic catalysis.

In this study, we show how in situ high-pressure pendant drop tensiometry and contact angle goniometry can be used to design surfactants for the CO2-water interface. This approach is used in quantifying the interfacial energy between CO2 and moieties that are potential surfactant tail candidates. A series of amphiphiles with biocompatible CO2-philic groups has been synthesized and their interfacial properties, including tension and contact angle at the water-CO2-silica interface, and emulsification capacity evaluated.

Keywords: compressed carbon dioxide; amphiphiles; interfacial tension; high-pressure contact angle goniometry, interfacial energy, emulsions and microemulsions.