Studying water in tight spaces

Abstract

Water is a versatile solvent that plays a significant role in many chemical systems, whether you’re studying a protein or a fuel cell. This versatility is rooted in water’s relatively high polarizability. Water molecules’ uneven charge distribution allows them to dissolve all sorts of charged and polar molecules. As a bulk solvent, water’s dielectric constant—a measure of its polarizability—is about 80. New experiments show that this value becomes dramatically smaller when water is trapped in small spaces (Science 2018, DOI: 10.1126/science.aat4191). The new measurement will improve modeling of molecular interactions in biology, energy systems, and elsewhere, writes Sergei V. Kalinin, a materials scientist at Oak Ridge National Laboratory, in a perspective accompanying the research paper. When water is confined in small spaces or forms a film on a surface, the molecules near the solid surfaces arrange themselves into layers and resist the changes in orientation that normally lead to polarization.