The discovery builds on an earlier advance by the same researchers. It had previously been shown that simple molecules can show some water-like features. In 2006, the collaborators published a paper showing that they could induce water-like peculiarities by adjusting the distance at which pairs of particles start to repel each other. Like water, their simulated substance expanded when cooled and became more slippery when pressurized. That finding led them to investigate more closely. They decided to look at how their simulated molecule acts as a solvent -- that is, how it behaves when other materials are dissolved into it -- because waters behavior as a solvent is also unique.
In their current paper, they simulated the introduction of oily materials into their imitator and showed that it had the same oil-water repulsion as real water across a range of temperatures. They also simulated dissolving oily polymers into their substance and, again, found water-like behavior. In particular, the polymers swelled not only when the water was heated, but also when it was super-cooled, which is one defining characteristic of real water. Proteins with oily interiors also behave in this way.
In real water, these special behaviors are thought to arise from waters structure -- two hydrogen atoms attached to an oxygen atom. The arrangement of electrical charges causes water molecules to twist and stick to each other in complex ways.
To create their simulation, the researchers ignored these complexities. They specified just two properties: the distance at which two converging particles start to repel each other an
|Contact: Steven Schultz|
Princeton University, Engineering School