Carbon dioxide is the cheapest solvent on earth after water. CO2 is not regulated by either the FDA or EPA, and it is fairly inert. Compressed CO2 has, therefore, been widely investigated as a potential replacement for conventional organic solvents. Stable aqueous aggregates in CO2 stabilized by surfactant molecules find applications in several areas including dry cleaning, enzymatic catalysis and nanoparticle synthesis. Colloidal dispersions in CO2 help overcome issues associated with the low solubility of both polar and high MW compounds in CO2. A lot of emphasis is being placed on designing effective amphiphiles for the CO2-water interface. Several tools have been used to identify active surfactants for CO2-based applications, including thermodynamic principles, computer simulations, pendant drop tensiometry, and scattering techniques. In this work we describe how combining results from high-pressure goniometry and tensiometry can be used to evaluate the interaction energies between CO2 and candidate CO2-philes. We address a long standing discussion on the nature of the interaction between CO2 and fluorocarbon and hydrocarbon moieties. High-pressure contact angle goniometry is a fairly new technique and it expected to contribute to the development of novel potential CO2-based applications including thin film deposition and cleaning in the microelectronic industry.
Keywords: compressed carbon dioxide, high-pressure contact angle goniometry, interfacial tension, amphiphiles, and interfacial energy.