Publications from each year can be found by following the navigation bar left. To read a particular article, click the title.

Surfactants at the Design Limit

This article analyzes how the individual structural elements of surfactant molecules affect surface properties, in particular, the point of reference defined by the limiting surface tension at the aqueous cmc, γ_cmc. Particular emphasis is given to how the chemical nature and structure of the hydrophobic tails influence γ_cmc. By comparing the three different classes of surfactants, fluorocarbon, silicone, and hydrocarbon, a generalized surface packing index is introduced which is independent of the chemical nature of the surfactants. This parameter ϕ_cmc represents the volume fraction of surfactant chain fragments in a surface film at the aqueous cmc. It is shown that ϕ_cmc is a useful index for understanding the limiting surface tension of surfactants and can be useful for designing new superefficient surfactants.

Surfactants for CO₂

For some 15 years the attainment of efficient, nonfluorinated CO₂-active surfactants has been a Holy Grail for researchers spanning pure and applied chemical sciences. This article tells the story of small-molecule CO₂-active surfactants, from the first tentative observations with fluorinated compounds in 1991 up to recently discovered fluorine-free oxygenated amphiphiles.

 

 

 

Properties of a Stilbene-Containing Gemini Photosurfactant: Light-Triggered Changes in Surface Tension and Aggregation

A new photosurfactant has been synthesized, and its photoreactions in water, interfacial properties, and changes in aggregation have been characterized. The compound is a stilbene-containing gemini photosurfactant (SGP), which is of interest because the headgroup spacer is a stilbene chromophore, and it may be prepared initially in the trans (E-SGP) form. Molecular simulations show that UV-induced reactions cause significant changes in molecular conformation and especially the relative orientation of hydrophobic chains. 1H nuclear magnetic resonance, UV−vis absorption, and liquid chromatography−mass spectroscopy results are consistent with photodimerization in aqueous solutions. Irradiation causes significant changes in surface tension (maximum Δγ = −12 mN m^-1) and wettability (Δθ = −15° on hydrophobic glass). Furthermore, small-angle neutron scattering shows the initial E-SGP form is present as large vesicle-like aggregates whereas the UV-induced dimer gives small 20 Å spherical charged micelles. These results demonstrate the importance of molecular design for generating effective and efficient photosurfactants.‌