To investigate if the amphiphilic feature exhibited in ionic liquids (ILs) with nonpolar cationic tails still exists in ILs with polar tails, by performing molecular dynamics simulations for 1-(8-hydroxyoctyl)-3-methyl- imidazolium nitrate (C-OH) and 1-octyl-3-methyl-imidazolium nitrate (C-8), we found that, in C-OH, cationic tail groups can no longer aggregate to form separated nonpolar tail domains, instead hydroxyl groups form a rich number of hydrogen bonds with other groups, indicating that the hydroxyl substituent changes the IL system from an amphiphilic liquid to a polar liquid. Due to the large amount of hydrogen bonds, C-OH has slower dynamics than C-8. (c) 2013 Elsevier B.V. All rights reserved.