Effect of the Addition of Water-Soluble Polymers on the Structure of Aerosol OT Water-in-Oil Microemulsions:  A Fourier Transform Infrared Spectroscopy Study

Abstract

Using Fourier transform infrared (FT-IR) spectroscopy and electrical conductivity measurements, the study of water-in-oil (w/o) microemulsions of Aerosol OT dissolved in toluene with different water contents, in the absence and in the presence of poly(vinylpyrrolidone) (MW 10 000), PVP K15, and poly(sodium 4-styrenesulfonate) (MW 75 000), PSS, has been carried out. Conductivity measurements show attractive interactions between droplets of w/o microemulsions without polymers containing high water contents, w 0 g 25. The addition of polymers prevents these interactions even at the lowest polymer concentration used in this work, 2%. From FT-IR spectra different micellar structures were detected in the absence of polymers, and vibrational modes of the surfactant molecule allow structural information to be obtained of each kind of aggregate. The structure of each kind of aggregate has a great dependence on the water content. Infrared spectra of the surfactant molecule of microemulsions containing different concentrations of PVP K15 and PSS were also recorded. The comparative analysis of these spectra with those in the absence of polymers permits, in a first place, localization of the polymer in the aqueous core and, later, study of the structural changes induced by the addition of these polymers.

The interaction between poly(vinylpyrrolidone) and reversed micelles of water/AOT/ n -heptane

“…In order to quantify the components of the hydroxyl and carbonyl stretching bands and their changes with polymer contents, the spectra have been subjected to a deconvolution process in Gaussion bands [17]. The measurements of FTIR are carried out as described in reference [25].…”

“…The bound water has some unusual properties, such as high microviscosity, no freezing point, and blocking of the formation of hydrogen bonds [1]. The water in a reversed micelle is similar to the water in a biomembrane in many aspects [11], and hence much attention has been paid to the state and structure of the water in reversed micelles and microemulsions [12,13,14,15,16,17]. People hope to mimic biomembranes and to disclose the biological physics and biological chemistry phenomena by investigating the water state in the reversed micelle and microemulsion.…”

Effect of the Solvent on the Water Properties of Water/Oil Microemulsions

“…In a previous paper we used IR spectroscopy to study the effect of the addition of water-soluble polymers on the structure of AOT/toluene w/o microemulsions (20). Results showed the existence of a fourth type of water molecule.…”

“…In particular, we discuss the spectrum of the water of the micellar core of AOT w/o microemulsions dissolved in cyclohexane and isooctane. Comparative analysis with spectra corresponding to microemulsions dissolved in toluene (20) allows us to obtain information on the effect of solvent on the waterentrapped structure. In addition, the UV-Vis absorption spectra of methyl orange solubilized in all microemulsions were recorded.…”

The Nanostructure Studies of Surfactant-Free-Microemulsions in Fragrance Tinctures

“…The elongation related to an OH-group is very interesting; it can be seen that by increasing the content of water in the system, it becomes wider, and finally, approaching the experimental path next to binodial curve, covers the whole area of 3000-3700 cm -1 . Firstly, after addition of water to studied system (ϕ w = 0.05) OH streching band is located in area of low frequency 3100-3300 cm -1 , which is attributed to full hydrogen bonding developed between interfacial water molecules and molecules of ethanol (having the role of surfactant in our system) 22,23 . The surface of the domains is expected to be covered with hydroxyl groups at saturation, producing a weakly associated interfacial surfactant film.…”