Study on surface tension of a series of 1-alkyl-3-methylimidazolium room temperature ionic liquids

A series of room temperature ionic liquids based on 1-CnH(2n+1)-3-methylimidazolium ([C(n)MiM]) with two kinds of fluorinated anions (BF4(-) and PF6-) (n=2 similar to 7; 4 similar to 7, respectively) were synthesized, and the structures were characterized and confirmed by I H NMR, IR and MS. Surface tensions were measured using a Wilhelmy plate apparatus over a wide temperature range (293 similar to 338 K). The results show that there is a linear decrease of surface tension with increasing temperature. The values of surface tension span an unusually wide range for compounds of similar structure, from 50.4 Mj/M-2 ([C(2)Mim]BF4) to 36.1 Mj/M2 ([C(7)mim]BF4) at 298 K. Surface properties of the series of synthesized ionic liquids were also discussed.