Surface structure of the mixture of 1-alkyl-3-methylimidazolium iodide and polyiodide observed by surface tension measurement and X-ray reflectivity

Synthesis and Micellization of Carbosilane Sulfonate Surfactants with Short Alkyl Chains

Carbosilane surfactants, consisting of carbosilane as a hydrophobic group linked to hydrophilic groups, are one kind of silicone surfactants. In this paper, a series of carbosilane sulfonate surfactants with short alkyl chains (Cn-Si2C-SO3Na (n = 1-6)), Me-Si2C-SO3Na, Et-Si2C-SO3Na, Pr-Si2C-SO3Na, Bu-Si2C-SO3Na, Pen-Si2C-SO3Na, and Hex-Si2C-SO3Na, were prepared and characterized by 29 Si NMR, 1H NMR, and FT-IR spectroscopies. The influence of the alkyl chain length on their micellization was studied using surface tension, dynamic light scattering, conductivity, and transmission electron microscopy. The CMC value decreases with increasing length of the short alkyl group. The γCMC value of Cn-Si2C-SO3Na (n = 1-6) increases as the alkyl chain increases from methyl to propyl, while the γCMC value gradually decreases as the alkyl chain increases from propyl to hexyl. The larger and rigid tetramethyldicarbosilane group functioned synergistically with a short alkyl chain, resulting in carbosilane sulfonate surfactants adsorbing at the air/water interface with a rugby ball shape; accordingly, the Amin values of the investigated carbosilane sulfonate surfactants increase with increasing length of the alkyl chain. The micellization process of carbosilane sulfonate surfactants is enthalpy-driven at lower temperatures and entropy-driven at high temperatures. The ΔHm0 values became more negative and ΔSm0 values more positive as the alkyl chain length increased. Aggregates in the range of 10-800 nm were observed for Cn-Si2C-SO3Na (n = 1-6) in an aqueous solution, and the hydrodynamic diameter (Dh) decreased with increasing length of the short alkyl group.

The Buoy Effect: Surface Enrichment of a Pt Complex in IL Solution by Ligand Design

The targeted enrichment of a Pt complex with an ionic liquid (IL)-derived ligand system in IL solution is demonstrated by using angle-resolved X-ray photoelectron spectroscopy. When the ligand system is complemented with fluorinated side chains, the complex accumulates strongly at the IL/gas interface, while in an equivalent solution of a complex without these substituents no such effect could be observed. This buoy-like behavior induces strong population of the complex at the outermost molecular layer close to surface saturation, which was studied over a range from 5 to 30 %_mol . The surface enrichment was found to be most efficient at the lowest concentration, which is particularly favorable for catalytic applications such as supported ionic-liquid-phase (SILP) catalysis.