The effect of temperature and sulfolane concentration on aqueous electrolyte with molecular crowding: A molecular dynamics simulation study

Molecular crowding agents can significantly suppress water activity by affecting hydrogen bonds. Here, we performed molecular dynamics simulation to study the effect of temperature and concentration of sulfolane, a crowding agent, on aqueous electrolytes. The mean square displacement, diffusion coefficient, coordination number, number density distribution, and average number of intermolecular hydrogen bonds were calculated and discussed. Due to the molecular crowding, the effect of temperature and sulfolane concentration on the average number of hydrogen bonds between water molecules is very interesting. When the concentration of sulfolane is low, the average number of hydrogen bonds between water molecules decreases monotonically with increasing temperature. However, when the concentration of sulfolane reaches a certain value, the average number of hydrogen bonds between water molecules no longer monotonically decreases but first increases and then decreases. When the concentration of sulfolane continues to increase, the average number of hydrogen bonds between water molecules tended to an abnormal monotonic increase. This work provides a deep study of the molecular crowding at the molecular level under wide ranges of temperature and concentration for designing aqueous electrolytes.