Aggregation of an ionic-liquid type hydrotrope 1-Butyl-3-methylimidazolium p-toluenesulfonate in aqueous solution.

Graphical abstract Abstract In this work, the aggregation behavior of 1-butyl-3-methylimidazolium p -toluenesulfonate (BmimTOS), a new type of cationic hydrotrope, was investigated, where two distinct inflection points C 1 and C 2 were reflected by the change of conductivity, micro-polarity, surface tension. Therefore, it is speculated that small aggregate was formed in BmimTOS aqueous solution after C 1 and structure change of these aggregates may be presented to form larger aggregates after C 2. The formation of aggregate and the change of the aggregate size were further confirmed by dynamic light scattering (DLS) measurements. However, as suggested by micro-polarity measurements, these aggregates are not typical micelle-like ones. Furthermore, such two-step aggregation behavior was shown to be presented at a wide temperature region from 288.15 K to 318.15 K; however, the phenomenon cannot be observed when the alkyl chain length on imidazolium cation was changed into ethyl-, hexyl-, or octyl-. [ABSTRACT FROM AUTHOR]