About the nanostructure of the ternary system water - [BMIm]PF6 - TX-100.

HYPOTHESIS: Many efforts have been made to formulate water-IL microemulsions. One of the most intensely studied systems is H2O - 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIm]PF6) - 4-octylphenol polyethoxylate (TX-100) and it is not questioned that this system forms microemulsions. The nanostructures observed for traditional microemulsions are postulated with the surfactant being adsorbed at the interface such that the hydrophilic EO sides intrude into the water domains, while the hydrophobic hydrocarbon chains are immersed into [BMIm]PF6. However, the high polarity of [BMIm]PF6 and the observation that [BMIm]PF6 mixes well with oligoethylene oxides but hardly with non-polar solvents like toluene or alkanes are not in line with this picture. EXPERIMENTS: We re-studied the ternary system H2O - [BMIm]PF6 - TX-100 by measuring phase diagrams, determining tie-lines, and carrying out ROESY NMR and PFG NMR measurements. FINDINGS: We found that the hydrophobic part of the surfactant interacts neither with water nor with [BMIm]PF6, while both solvents interact with the hydrophilic part of the surfactant. We suggest that the surfactant is not adsorbed at the interface between water and the IL, but forms normal spherical or elongated micelles or even continuous aggregates with the hydrocarbon chains forming the interior of the aggregates.

Tailored ionic liquid-based surfactants for the formation of microemulsions with water and a hydrophobic ionic liquid.

Microemulsions (µe) with water and a hydrophobic ionic liquid (IL) usually require 45-60 wt% surfactant to solubilize equal amounts of water and IL. To increase the efficiency we designed a new class of surfactants by combining a hydrophilic but IL-ophobic carbohydrate-based part with a hydrophobic but IL-ophilic IL-based part. These surfactants allow formulating microemulsions with 20 wt% surfactant only which opens up a new arena for efficient water-IL µes.

Chiral heliconical ground state of nanoscale pitch in a nematic liquid crystal of achiral molecular dimers.

Freeze-fracture transmission electron microscopy study of the nanoscale structure of the so-called "twist-bend" nematic phase of the cyanobiphenyl (CB) dimer molecule CB(CH2)7CB reveals stripe-textured fracture planes that indicate fluid layers periodically arrayed in the bulk with a spacing of d ~ 8.3 nm. Fluidity and a rigorously maintained spacing result in long-range-ordered 3D focal conic domains. Absence of a lamellar X-ray reflection at wavevector q ~ 2π/d or its harmonics in synchrotron-based scattering experiments indicates that this periodic structure is achieved with no detectable associated modulation of the electron density, and thus has nematic rather than smectic molecular ordering. A search for periodic ordering with d ~ in CB(CH2)7CB using atomistic molecular dynamic computer simulation yields an equilibrium heliconical ground state, exhibiting nematic twist and bend, of the sort first proposed by Meyer, and envisioned in systems of bent molecules by Dozov and Memmer. We measure the director cone angle to be θ(TB) ~ 25° and the full pitch of the director helix to be p(TB) ~ 8.3 nm, a very small value indicating the strong coupling of molecular bend to director bend.

Liquid crystallinity and supramolecular organization of regioisomeric isatin derivatives: an experimental and theoretical study.

Spatially organized chromophores can be beneficial for advanced applications like for example, organic solar cells, laser technology or non-linear optic devices as well as supramolecular photochemistry. Of particular interest are non-static ordered forms of molecular organization as for example, liquid crystals. With this in mind we synthesised four new regioisomeric isatin derivatives by Suzuki-Miyaura coupling of 4-dodecyloxyphenylboronic acid with all four possible regioisomers of bromoisatin. Liquid crystalline properties are found for 5-(4-dodecyloxyphenyl)isatin, while the other regioisomers do not display a mesomorphic behaviour. The synthesis, physicochemical investigations including polarization microscopy, differential scanning calorimetry and X-ray investigations are discussed and accompanied with density functional theory calculations with respect to the target molecules and their possible H-bonded aggregates. Two distinct setups of supramolecular assemblies for such isatin derivatives are discussed and a model for the mesophase is proposed.