A Molecular Expression for "Line Tension".

"Line tension", a concept that features in an additional term to the Young's equation, was introduced to describe the size dependence of contact angles of nanodroplets on surfaces. Although this concept describes the observations in a succinct, elegant manner, theorists have long had misgivings about the physical interpretation of the phenomenon. Papers have been published that attempt to nail down its value, which is reportedly very small (∼10 pN) and evidently even the sign has been uncertain.

Molecular Insights into Water Clusters Formed in Tributylphosphate-Di-(2-ethylhexyl)phosphoric Acid Extractant Systems from Experiments and Molecular Dynamics Simulations.

Di-(2-ethylhexyl)phosphoric acid (D2EHPA) and tributylphosphate (TBP) are two of the most studied and researched organophosphorous extractants. D2EHPA is an acidic extractant, offering both hydrogen bond donor and acceptor sites while TBP, a neutral extractant, only offers a single acceptor site per molecule. In spite of this, it is observed that 1 M D2EHPA in dodecane is a poorer extractant for water than 1 M TBP in dodecane.

Molecular origins of fluorocarbon hydrophobicity.

We have undertaken atomistic molecular simulations to systematically determine the structural contributions to the hydrophobicity of fluorinated solutes and surfaces compared to the corresponding hydrocarbon, yielding a unified explanation for these phenomena. We have transformed a short chain alkane, n-octane, to n-perfluorooctane in stages. The free-energy changes and the entropic components calculated for each transformation stage yield considerable insight into the relevant physics.