The effect of salt on the critical behaviour of non-ionic micellar solutions

Lower consolute boundaries of the nonionic surfactant C8E5 in aqueous alkali halide solutions: An approach to reproduce the effects of alkali halides on the cloud-point temperature

“…In this interaction the hydrophilic parts have an important role, in that they are in direct contact with the surrounding solution [55]. When thinking that a first cation-anion pair is introduced in the micellar solution, into the vicinity of the hydrophilic part, most likely this contact will be affected, either positively or negatively [26]. The previously added pair of ions is expected to influence the system so that the subsequently added pair encounters a slightly changed environment.…”

“…This study builds on the material of an earlier report, on how alkali halides change the properties (position in temperature and shape) of the lcb of C 8 E 5 [17]. There are definite advantages in using aqueous solutions of C 8 E 5 in that quite extensive results from spectroscopic [9,[22][23][24][25][26][27], thermodynamic [28][29][30][31], and modelling [32,33] studies exist. The effects of the presence of alkali halides in C 8 E 5 micellar solutions have been studied by time-resolved fluorescence quenching (aggregation behaviour and dynamics) [9], dynamic light scattering (particle and collective properties) [26], mixing calorimetry (apparent enthalpy of the surfactant) [31], and by a statistical-thermodynamical model (consolute boundaries) [33].…”

“…There are definite advantages in using aqueous solutions of C 8 E 5 in that quite extensive results from spectroscopic [9,[22][23][24][25][26][27], thermodynamic [28][29][30][31], and modelling [32,33] studies exist. The effects of the presence of alkali halides in C 8 E 5 micellar solutions have been studied by time-resolved fluorescence quenching (aggregation behaviour and dynamics) [9], dynamic light scattering (particle and collective properties) [26], mixing calorimetry (apparent enthalpy of the surfactant) [31], and by a statistical-thermodynamical model (consolute boundaries) [33]. Surfactants can also exhibit, instead of a lcb, an upper consolute boundary (ucb) in the (T , c CE ) diagram (inside the range 273.15 to 373.15 K), as it has been established with the zwitterionic surfactant dioctanoyl phosphatidyl choline (C 8 -lecithin), and in that case, e.g., NaCl and NaI shift the temperature-position of the boundary in the opposite directions as compared to the systems including oxyethylene-based solutes [34,35].…”

Effect of temperature on pseudoternary system Tween-80–butanol–hexane–water

“…Kahlweit et al [16,17] found a regular Hofmeister trend for such class of surfactants: a lyotropic salt such as NaCl decreases the CP whereas the opposite effect is observed with a hydrotropic salt such as NaClO 4 . The interpretation of these effects is not well understood [18][19][20]. The commonly accepted explanation is related to the ability of ions to disrupt or enhance the water structure [21] which affects the number of water molecules available for solvation.…”

Effect of Recognized and Unrecognized Salt on the Self-Assembly of New Thermosensitive Metal-Chelating Surfactants

“…Kahlweit et al , found a regular Hofmeister trend for the C i E j surfactants: a lyotropic salt such as NaCl decreases the cloud point whereas the opposite effect is observed with a hydrotropic salt such as NaClO 4 . The interpretation of these effects is not well understood. − The commonly accepted explanation is related to the ability of ions to disrupt or enhance the water structure, which affects the number of water molecules available for solvation. Kalbanov et al explained the salting effect by the depletion/adsorption of one of the ions at the polar−apolar layer within the micelle.…”