In　this　study,　a　molecular　simulation　(Gaussian03)　was　used　to　analyze　the　chemical　structure　of　4-dimethylaminopyridine　(DMAP)　to　investigate　its　use　for　the　synthesis　of　ionic　liquids　(ILs).　Based　on　DMAP,　a　series　of　new　ILs　was　prepared　and　characterized　by　fourier　transform　infrared　spectroscopy　(FT-IR),　H-1　nuclear　magnetic　resonance　(H-1-NMR),　thermogravimetric　analysis　(TGA),　and　differential　scanning　calorimeter　(DSC).　The　density　data　of　the　studied　ILs　were　measured　from　328.15　K　to　358.15　K,　p　=　0.101　MPa.　It　is　shown　that　density　decreases　with　an　increase　in　the　temperature　and　the　alkyl　chain　length　of　cations.　And　density　is　also　affected　by　the　anion　type.　Furthermore,　the　volume　of　ions,　NBO　charges,　and　the　interactions　of　anions　and　cations　were　calculated　by　Gaussian03　to　explain　the　obtained　density　results.　The　second-order　polynomial　equation　was　adopted　to　correlate　the　relationship　of　density　and　temperature.　Then,　an　isobaric　thermal　expansion　coefficient,　molecular　volume,　and　lattice　potential　energy　were　obtained　from　the　density　data.　Viscosity　was　determined　from　323.15　K　to　368.15　K,　p　=　0.101　MPa.　It　is　determined　that　the　viscosity　of　ILs　decreases　with　an　increase　in　the　temperature　but　increases　with　an　increase　in　the　alkyl　chain　length　of　cations.　The　temperature　dependence　of　viscosity　was　described　by　the　Vogel-Fulcher-Tamman　(VFT)　model,　and　the　activation　energy　of　viscous　flow　(E-eta)　was　obtained.　Furthermore,　the　decomposition　temperature　(T-d),　glass　transition　temperature　(T-g),　and　melting　temperature　(T-m)　of　ILs　were　obtained　from　the　results　of　TGA　and　DSC.　(C)　2019　Elsevier　B.V.　All　rights　reserved.