Critical adsorption and boundary layer structure of 2-butoxyethanol+D2O mixtures at a hydrophilic silica surface

Abstract

Neutron reflectivity experiments have been performed to investigate the adsorption behavior of aqueous solutions of n-2-butoxyethanol (n-C4E1) and i-2-butoxyethanol (i-C4E1) in D2O against a hydrophilic silica substrate. The measurements were made in the one-phase region near the lower critical solution point of the aqueous systems. At temperatures removed from the lower critical solution temperature, TLCS, evidence for the existence of a microscopically thick (∼40 Å) adsorbed D2O-rich layer is presented along with data suggesting that the amphiphile is strongly depleted from the boundary layer. Experiments using a thick “tuning” layer of silica reinforce these observations. Analysis of the data as T→TLCS reveals that the region beneath the adsorbed D2O-rich layer becomes increasingly enriched with D2O, and the nature of the composition profile normal to the interface has been considered. Analysis identifies the exponent describing the power-law decay part of the critical adsorption profile appended to the D2O-rich region and associates a temperature-dependent correlation length with the critical adsorption profile. Ellipsometric data are presented which complement the neutron reflectivity results. The adsorption behavior of the n-C4E1 and i-C4E1 systems are found to be very similar with the only discernible difference being the magnitude of the adsorption preference of water for the n-C4E1 system in the long-range profile.

Temperature responsive behavior of polymer brush/polyelectrolyte multilayer composites

“…Detailed descriptions can be found in previous studies. 36,37 Heavy water, D 2 O, was injected into the trough, and the samples were left equilibrating for at least 1 h prior to measurement. The Motofit package 38 running in the Igor Pro environment (Wavemetrics) was used to fit the measured reflectivity curves, using a model to gain the corresponding SLD profiles.…”

Effect of ionic strength and type of ions on the structure of water swollen polyelectrolyte multilayers

“…A more detailed description of the sample cell is given elsewhere. 33 All measurements were conducted at room temperature. Neutron reflectivity measurements were performed at the V6 instrument at the HZB Berlin.…”

Neutron Reflectivity as Method to Study in‐Situ Adsorption of Phospholipid Layers to Solid‐Liquid Interfaces

“…The measurements were performed using the solid-liquid experimental cell at the instrument V6 at BENSC, Berlin. [25] Reference measurements on the thickness of the bare PE layer against D 2 O were performed first. Freshly sonicated protonated DMPC vesicles (1 mg/ml) in 0.5 M sugar solution in D 2 O were deposited at the surface of the protonated polyelectrolyte coated Si blocks by self-assembly.…”

“…[25] Fluids could be filled through stainless steel inlet and outlet tubes that were mounted in opposite corners of the trough. The trough-silicon sandwich was clamped between two thermostated aluminium supports allowing for temperature adjustment within ± 0.5 K. The Teflon trough and the silicon surface were cleaned prior to the incorporation into the sample cell by sonication in aqueous HELMANEX solution and by standard RCA-method, respectively.…”