Effect of Cosolvents and Cosolutes upon Aggregation Transitions in Aqueous Solutions of the Poloxamer F87 (Poloxamer P237):  A High Sensitivity Differential Scanning Calorimetry Study

Abstract

The effects of a number of different cosolvents and cosolutes upon the micellization of the oxyethylene/oxypropylene/oxyethylene block copolymer F87 (P237; 70% oxyethylene and 30% oxypropylene) have been investigated using high-sensitivity differential scanning calorimetry (HSDSC). The calorimetric output has been analyzed using a model fitting procedure to obtain estimates for various thermodynamic parameters which characterize the micellization event as observed by HSDSC. These important parameters include T 1/2, the temperature at which the micellization process is half-completed, ΔH cal, the calorimetric enthalpy for the process which is measured by integration of the calorimetric output; ΔH vH, the van't Hoff enthalpy; and n the aggregation number. From this data it has been possible to measure critical micelle concentrations (cmcs). The experimental investigations reveal that methanol, ethanol, urea, and formamide prevent the onset of micellization, while butanol and hydrazine favor micelle formation. Finally a thermodynamic model simulation is developed and presented which appears to be capable of explaining the major effects of methanol upon micellization.

Natural product mixture analysis by matrix-assisted DOSY using Brij surfactants in mixed solvents

“…For Brij 78, these solutions were in 20% DMSO-d 6 -80% D 2 O (v/v) and for The CMC behavior of various PEO-block copolymers has been investigated in water-ethanol mixed solvents. [33][34][35] These studies have shown that the CMC increased aer addition of ethanol. The addition of DMSO-d 6 to D 2 O seems to show the same tendency, providing better solvent conditions for the Brij 78 and 98 compared to pure D 2 O and disfavoring the formation of micelles (self-assembly).…”

What can isothermal titration microcalorimetry experiments tell us about the self‐organization of surfactants into micelles?

“…Aggregation process can be described by Equation 5 in which (n) molecules of surfactant S form one aggregate of aggregation number (n), (Tanford, 1980;Armstrong et al, 1996):…”

Adsorption of a Polymeric Siloxane Surfactant on Carbon Black Particles Dispersed in Mixtures of Water with Polar Organic Solvents

“…The solvent quality is a controlling factor in the self-assembly of polymeric surfactants (16,17). In the case of poly(ethylene oxide)-poly(propylene oxide) (PEO-PPO) surfactants, where water is typically used as a solvent (being selective for PEO), the addition to water of solvents such as glycerol, ethanol, or formamide (18)(19)(20)(21)(22)(23) provides extra degrees of freedom in tailoring the solution properties (17,(24)(25)(26)(27). In general, the published information on the effects of polar organic solvents on the self-assembly of polymeric surfactants and on their interactions with colloidal particles is limited.…”