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Adsorption of surfactants on solids is affected by the intermolecular packing in the adsorbed layer besides the driving forces. The adsorption behavior of a double-chain surfactant on silica is studied here along with that of the single-chain one. Comparison of adsorption of these two surfactants is warranted since while the single-chain surfactants form spherical micelles, the double-chain ones form bilayered vesicles in solution. While the adsorption of the single-chain surfactant reaches the plateau in a wide concentration range, the adsorption of the double-chain one increases sharply in a concentration range 10 −5 mol/L up to the plateau. The single chain is found to form ∼1.5 monolayers under saturation coverage suggesting adsorption with reverse orientation at high concentration. In contrast, the adsorption of the double-chain surfactant under saturation coverage is equivalent to a ∼0.9 monolayer. Fluorescence tests revealed the hydrophobicity change of the surface with increase in adsorption. However, the hydrophobicity tests show the solid surface to be hydrophilic in this range; the double-chain surfactant is proposed to form a partial bilayer.

The property of synthetic dialkyl amphiphiles to form vesicular structures can be exploited in a variety of situations, such as mimicking biological membranes, drug delivery, studies related to artificial photosynthesis, aggregates on solids, etc. The stability and thermotropic behavior of liposomes from natural lipids could be improved by synthetically modifying the alkyl chains of the lipids or by using totally synthetic structures. This article, which highlights the important milestones in the development of vesicular structures from synthetic amphiphiles, encompasses a brief description of investigations reporting the introduction of totally synthetic dialkyl amphiphiles, mixtures of monoalkyl cationic and anionic amphiphiles, hyperextended alkyl amphiphiles, and so on. Furthermore, most of the relevant work in the last decade relating to bilayer formation from synthetic amphiphiles is documented here.

The adsorption of polyacrylic acid onto an alumina surface is shown using fluorescence spectroscopy to be followed by a rearrangement of its macromolecular segments in the adsorbed state. The adsorption of pyrene-labelled polyacrylic acid has been investigated from its solutions and from solutions mixed with unlabelled acid. The excimer efficiency of the emission of the pyrene-labelled polymer species indicates a pH-independent equilibrium conformation of adsorbed polymer chains. While the slow conformational rearrangement may not affect rapid flocculation processes, it could affect slow flocculation as well as deaggregation and reaggregation processes.

The binding of Ru(bpy) 2+ 3 onto Nafion membrane (H + form) is complete in about 20 h and a binding maximum of about 10 −5 mol mg −1 has been arrived at from absorption studies. The binding of Ru(bpy) 2+ 3 from a saturated solution of 7-amino-4-methylcoumarin (C120) and Ru(bpy) 2+ 3 also yielded a similar isotherm, but a low binding maximum of Ru(bpy) 2+ 3 was recorded. The binding process studied on Li + - and Cs + -exchanged Nafion forms indicated that while the binding density was enhanced marginally on the Li + form (compared to the H + form), there was practically no binding on the Cs + form. Absorption and luminescence studies on Ru(bpy) 2+ 3 bound to Nafion indicated that the spectra were shifted to blue. In the case of absorption, both the metal-to-ligand charge transfer (MLCT) and π→π* states shifted to the blue, but the luminescence spectra of C120 moved progressively to the red as the binding density increased. Direct interaction between C120 and Ru(bpy) 2+ 3 is observed from luminescence studies as shown by an isoemissive point in the combined luminescence spectra. A static quenching mechanism between C120 and Ru(bpy) 2+ 3 is inferred in the bound state also, as is shown in the case of a homogeneous solution. The Ru(bpy) 2+ 3 emission bound to the Li + form underwent a blue shift at higher loading.