Dynamics of water filaments in disordered environments.

The formation, stability, and dynamics of water filaments in disordered environments is investigated by using atomistic molecular dynamics simulations. It is found that in an alkyl-chain arrangement representative of that used in liquid chromatography, extended water filaments can form for up to 1 ns before they are destroyed again due to thermal fluctuations. The water dynamics in the disordered stationary phase is surprisingly intense with about 10(7) per alkyl chain per second of water molecules flowing in and out of the stationary phase. This is compatible with estimates based on Fick's law using a homogeneous solubility-diffusion model. The simulations also establish the existence of different types of water molecules as was predicted 30 years ago. From the current simulations they can be identified as (SiOH-) surface-bound, interfacial, and bulk water molecules.