Molecular Interactions Leading to the Coadsorption of Surfactant Dodecyltrimethylammonium Bromide and Poly(styrenesulfonate) at the Oil/Water Interface

Abstract

The strong synergistic adsorption of mixed polymer/surfactant (P/S) systems at the oil/water interface shows promise for applications such as oil remediation and emulsion stabilization, especially with respect to the formation of tunable mesoscopic multilayers. There is some evidence that a combination of dodecyltrimethylammonium bromide (DTAB) and sodium poly­(styrenesulfonate) (PSS) exhibits the adsorption of a secondary P/S layer, though the structure of this layer has long eluded researchers. The focus of this study is to determine whether the DTAB-assisted adsorption of PSS at the oil/water interface occurs as a single layer or with subsequent multilayers. The study presented uses vibrational sum-frequency spectroscopy and interfacial tensiometry to determine the degree of PSS adsorption and orientation of its charged groups relative to the interface at three representative concentrations of DTAB. At low and intermediate DTAB concentrations, a single mixed DTAB/PSS monolayer adsorbs at the oil/water interface. No PSS adsorbs above the system critical micelle concentration. The interfacial charge is found to be similar to that of P/S complexes solvated in the aqueous solution. The surface adsorbate and P/S complexes in the bulk both exhibit a charge inversion at around the same DTAB concentration. This study demonstrates the importance of techniques which can differentiate between coadsorbing species and calls into question current models of P/S adsorption at an oil/water interface.

Surfactant Adsorption to Different Fluid Interfaces

“…In Figure , Π cmc is plotted over initial interfacial tensions for the o/w and a/w interfaces, showing the effect of oil polarity on the maximum interfacial pressure. Additionally, data from the literature is added to the graph. ,− ,,− The measured and literature data are listed in Tables S1–S4 of the Supporting Information and include only data measured at pH 7 with a salt concentration between 0 and 10 mM. Generally, salt affects the interfacial packing, interfacial tension, and cmc of the surfactant (especially ionic surfactants).…”

Playing Favorites: Preferential Adsorption of Nonionic over Anionic Surfactants at the Liquid/Liquid Interface

“…For these studies, a solvent phase of H 2 O produces the VSF signal in both the C–H stretching region (2800–3100 cm –1 ) due to its O–H stretching modes as well as the C–D stretching region (2000–2250 cm –1 ) likely due to the bend + libration combination mode of H 2 O molecules. − (Figure S1 in the Supporting Information shows and discusses the presence of these aqueous modes in further detail). Thus, D 2 O was chosen as the aqueous phase to minimize spectroscopic interferences in the C–H stretching region, similar to previous VSF studies. − …”

“…The experimental cell used to hold the oil/water systems in this work is custom-built and has been used extensively in previous studies from this lab, where the volume of the aqueous layer is 10 mL and that of the oil layer is approximately 20 mL. − , Using a “bottom-up” configuration, visible and IR beams approach the interface through the CCl 4 layer with incident angles relative to the interfacial normal of 66 and 75°, respectively. These angles were chosen such that the system achieves total internal reflection.…”

“…All spectra reported here are an average of at least three spectra taken on three separate days with a minimum of 550 shots per point. To account for any changes in beam intensities with IR frequency, each spectrum has been normalized to the sum-frequency spectrum of a nonresonant signal generated off a gold mirror submerged in CCl 4 (in PPP polarizations), following the practice of previous Richmond lab publications. − , This normalization results in the arbitrary unit (au) scales reported as the y -axis in all spectra presented here.…”

An Advanced Material with Synergistic Viscoelasticity Enhancement of Hydrophobically Associated Water‐Soluble Polymer and Surfactant

“…Polymer–surfactant composites have become a research hotspot both in academia and industry for the past decades because of its particular synergistic behaviors. [ 1–12 ] They have a wide range of applications in many industrial formulations, such as laundry detergents, [ 13,14 ] cosmetics, [ 15 ] drug deliveries, [ 16–20 ] petroleum productions, [ 21–23 ] and so on. In this regard, researchers have proposed several synthetic strategies for preparing hydrophobically associated water‐soluble polymers (HAWSPs) such as: inverse emulsion polymerization, post modification process, solution polymerization, and micellar polymerization.…”