Influence of NaCl on the Behavior of PEO−PPO−PEO Triblock Copolymers in Solution, at Interfaces, and in Asymmetric Liquid Films

Abstract

The solution behavior of the polymeric surfactant Pluronic F127 (PEO(99)PPO(65)PEO(99)) and its adsorption behavior on aqueous-silica and aqueous-air interfaces, as well as the disjoining pressure isotherms of asymmetric films (silica/aqueous film/air) containing F127, are studied. The interfacial properties of adsorbed F127 layers (the adsorbed amount Gamma and the thickness h) as well as the aqueous wetting film properties [film thickness (h) and refractive indexes] were studied via ellipsometry. The solution properties of F127 were investigated using surface tensiometry and light scattering. The interactions between the air-water and silica-water interfaces were measured with a thin film pressure balance technique (TFB) and interpreted in terms of disjoining pressure as a function of the film thickness. The relations between the behaviors of the asymmetric films, adsorption at aqueous air, and aqueous silica interfaces and the solution behavior of the polymeric surfactant are discussed. Special attention is paid to the influence of the concentrations of F127 and NaCl. Addition of electrolyte lowers the critical micelle concentration, diminishes adsorption on silica, and increases the thickness of the asymmetric film.

Polymeric micelles: authoritative aspects for drug delivery

“…The effect of salt concentration on CMC has been studied by Elisseeva et al [151]. CMC of Pluronic F127 was strongly influenced by the salt concentration and the presence of 0.1 M sodium chloride decreased the CMC of Pluronic F127 by a factor of 2.…”

Thermodynamic properties of aqueous polypropylene oxide 400 solutions from isopiestic measurements over a range of temperatures

“…These may have either a block structure as the much-studied (EO) x (PO) y (EO) x triblock copolymer [1][2][3][4][5][6][7][8][9], often referred to as Pluronic polymers, or a random distribution of PO and EO units, often referred to as Ucon polymers. A typical feature of polypropylene oxide (PPO) and polyethylene oxide (PEO) as well as copolymers of PO and EO is their reduced solubility in aqueous solution with increasing temperature.…”

Thinning of wetting films formed from aqueous solutions of non-ionic surfactant

“…The results presented in the current paper are in line with these effects. In our previous investigation [2] we found thick wetting films on silica formed from an aqueous solution of the triblock copolymer 'Pluronic F127' (PEO 99 -PPO 65 -PEO 99 ). In contrast with [3][4][5], we observed a pronounced increase of the thickness upon increasing of the NaCl concentration at a constant hydrostatic pressure [2].…”

“…In our previous investigation [2] we found thick wetting films on silica formed from an aqueous solution of the triblock copolymer 'Pluronic F127' (PEO 99 -PPO 65 -PEO 99 ). In contrast with [3][4][5], we observed a pronounced increase of the thickness upon increasing of the NaCl concentration at a constant hydrostatic pressure [2]. This observation was rather unexpected; firstly, because electrostatic repulsion diminishes upon increase electrolyte concentration, secondly, because the amount of adsorbed F127 at silica was shown to decrease with increasing NaCl concentration.…”

“…It is also possible to compute the film thickness using the six-layer model: silicon (n = 3.85)/silicon oxide (n = 1.46, h = 2 nm)/F127 adsorbed layer at the silica-water interface/aqueous film/F127 adsorbed layer at the air-water interface/air. In this model the film is 'divided' into sublayers: F127 layer at the air-water interface (n = 1.38, h 1 ∼ 7 nm [2])/aqueous core (n sol depends on the C F127 , h 2 should be calculated)/F127 layer at the silica-water interface (n = 1.38, h 3 is taken from our previous data [2]), where the h film equal to the sum of these sublayers:…”