The Effects of Salts on the Lower Consolute Boundary of a Nonionic Micellar Solution

Modeling of phase separation in PEG–salt aqueous two‐phase systems

“…Hence, varying the osmotic pressure in our model mixture is equivalent to varying the combined overall concentration of PEG and salt in the mixture (or the overall volume fraction, 7) prior to phase separation. This approach of using the osmotic pressure as a variable to change the equilibrium concentration of a phaseseparating mixture is not unusual and has been used by several investigators while modeling phase separation in polymer-colloid mixtures (Gast et al, 1983a,b), aqueous mixtures of polymer and protein (Vlachy et al, 1993;Hall, 1990, 1992), micelle-water solutions Tau, 1984, 1985;Menon et al, 1991;Shukla and Rajagopalan, 1993), and micelle-salt-water mixtures (Kenkare et al, 1996).…”

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

“…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].…”

Performance of New Biodegradable Di‐Sulfonate Surfactants as Hydrotropes in High‐Temperature and Salinity Environments

“…However, it can be manipulated (increased or decreased) by the presence of additives such as electrolytes, ionic surfactants, alcohols, classical hydrotropes, etc. [4,[29][30][31][32][33]. Upon reaching this cloud point temperature, nonionic surfactants become unstable in the aqueous environment and separate into surfactant-rich and surfactant-poor phases.…”