Reverse aqueous emulsions and microemulsions in HFA227 propellant stabilized by non-ionic ethoxylated amphiphiles.

In this work we use in situ high-pressure tensiometry to screen non-ionic ethoxylated surfactants at the 1,1,1,2,3,3,3-heptafluoropropane (HFA227) propellant|Water (HFA227|W) interface. The EO(n)PO( approximately )(30)EO(n) series, where EO stands for ethylene oxide and PO for propylene oxide, and n the number of repeat EO units, was selected for this study based on the favorable interactions reported between HFA propellants and the PO moiety. The surfactants used in FDA-approved pressurized metered-dose inhaler formulations were also investigated.

Ethoxylated copolymersurfactants for the HFA134a- interface: interfacial activity, aggregate microstructure and biomolecule uptake.

In this work we examine the aggregation behavior of ethoxylated copolymer surfactants in 1,1,1,2-tetrafluoroethane in the presence of water, and the ability of such aggregates to uptake a model biomolecule. Our approach consists of developing a rational framework for understanding the behavior of interfacially active species at the HFA134a-water (HFA134a|W) interface using a combination of in situ high-pressure tensiometry, spectroscopy, and small-angle neutron scattering (SANS). The optimum hydrophilic-to-HFA-philic balance (HFB) for the ethylene oxide-propylene oxide-ethylene oxide (EOnPO∼43EOn, where subscripts indicate the number of repeat units) surfactant series at the HFA134a|W interface was determined at 298 K and saturation pressure of the propellant (under pressure).

Surfactant design for the 1,1,1,2-tetrafluoroethane-water interface: ab initio calculations and in situ high-pressure tensiometry.

In situ high-pressure tensiometry and ab initio calculations were used to rationally design surfactants for the 1,1,1,2-tetrafluoroethane-water (HFA134a|W) interface. Nonbonded pair interaction (binding) energies (E(b)) of the complexes between HFA134a and candidate surfactant tails were used to quantify the HFA-philicity of selected moieties. The interaction between HFA134a and an ether-based tail was shown to be predominantly electrostatic in nature and much more favorable than that between HFA134a and a methyl-based fragment.