Abstract
Owing to low melting point (<100 degrees C), negligible vapor pressure, and broad spectrum of applications, ionic liquids have gained much attention in the recent years. In this paper, the effects of temperature, polyvinyl pyrrolidone (PVP) polymer, and salts on the interfacial and bulk properties of aqueous solution of long-chain ionic liquid [i.e., 3-dodecyl-1-methyl-1H-imidazol-3-ium-bromide (C12mimBr)] were investigated using tensiometry. This long-chain ionic liquid was found to behave like a conventional surfactant, and thus it can be called surface active ionic liquid (SAIL). An inflection point in surface tension versus concentration curve at specific concentration was observed, which is termed the critical micelle concentration (CMC) of C12mimBr. The pre-micellar region was used to calculate various surface active parameters whereas the CMC was used to investigate its micellar behavior. Both surface activity and CMC of SAIL increased with the increase in temperature. No prominent effect was observed with the addition of PVP, whereas NaCl and CuNO3 addition distinctly changed the CMC. Similarly, surface effectiveness (pi(cmc)) of C12mimBr decreased with the addition of NaCl and increased with the addition of CuNO3, whereas addition of PVP showed no effect on it. It shows that PVP has negligible interaction with C12mimBr. Further, the process of micellization was found to be entropy driven.