The neat and aqueous solutions of the cholinium glycinate ionic liquid (IL), [Cho]­[Gly], at different water mole fractions, x ws, are studied by molecular dynamics simulations. The changes in the local nanostructure of systems with composition have been determined by calculation of various structural distribution functions. Hydrogen bond (H-bond) attractions determine the major relative orientations of the oppositely and like charged nearest neighbors. The cation–anion H-bonds mainly form between the hydrogen of the hydroxyl or methyl groups of the cation and the carboxylate oxygen of the anion. A preferred (antiparallel) arrangement between adjacent [Cho]+ cations is due to the effective H-bond between the hydroxyl oxygen and the methyl hydrogen sites that promotes the like-charge cluster formation. Adding water decreases the occurrence probability of the [Cho]+···[Gly]−···[Cho]+ bridge structure in the aqueous solutions due to the formation of the [Gly]−···HOH···[Gly]− structure via H-bonding. Observed density trend versus x w is interpreted based on an interstice model and investigating the water cluster size distribution. Finally, the effect of x w on the infrared (IR) vibrational spectra were studied and blue and red shifts were observed for the stretching and bending vibrational modes of the hydroxyl group of [Cho]+, respectively. Current findings will improve the efficient engineering design and task-specific applications of aqueous solutions of bio-ILs consist of [Cho]+ and amino acid anions.

MD simulations are used to study the biocompatible IL [Cho][Gly], confined between two parallel plates of rutile or graphite. Both the structure and dynamical behavior of the confined IL are very heterogeneous and depend effectively on the position of the ions to the pore walls. The ion z-density profile is used for segmentation of the inter-wall space into a central region and two outer layers. The behavior of ions in the central region is very similar to the bulk IL, while the behavior of the arranged ionic layers adjacent to the pore walls show the clear deviation from the bulk IL due to confinement. In general, the confined IL shows a "solid-like" dynamics at T = 353 K, especially in the outer layers near the walls as well as in the z-direction. The presence of the "IL-rutile wall" electrostatic interaction and hydrogen bonding (H-bonding) causes a significant difference in the local structure and dynamics of the IL adjacent to the rutile walls versus the graphite walls. Simulation reveals a significant decrease in the average number of key cation-anion H-bonds at the outer layers relative to the central regions of both confined systems. Recognized [Cho]+···[Gly]-···[Cho]+ bridge structure at the central region is lost in the vicinity of the rutile walls due to inaccessibility of the hydroxyl hydrogen atom, which forms a stable H-bond with the rutile oxygen site. However, another unprecedented [Gly]- bridge is confirmed and preserved near the graphite walls and cations prefer to stay parallel to the wall surface.