Enthalpies of mixing a non-ionic surfactant with water at 303.15 K studied by calorimetry

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

“…That is, changes in the significant interactions of the polar (-O-and -OH) and hydrophobic (-CH 2 CH 2 -) groups of the nonionic solutes with the surrounding water weaken when m XY increases. There is, for example, evidence from calorimetric experiments that several alkali halides (NaF, NaCl, KCl and CsCl) increase the apparent enthalpy of C 8 E 5 [31]. The solubility of the macroentities, in a sequential chain of events, is initially changed in line with the existence of regions with altered electrolyte amounts that surround them.…”

“…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 the side chain of N-acyl amino acid surfactants on micelle formation: An isothermal titration calorimetry study

“…Especially, isothermal titration calorimetry (ITC) has been widely employed for the investigations of micelle formation [28][29][30][31][32][33][34][35][36][37]. From a thermodynamic point of view, one of the main advantages of titration calorimetry is considered to be that the partial molar enthalpy change of the solute, which can be approximately and directly evaluated from the experimental results obtained by dividing the titration heat by the number of moles of injected solute.…”