2785-54-8Relevant articles and documents
Liquid-crystalline ionic liquids
Bowlas, Christopher J.,Bruce, Duncan W.,Seddon, Kenneth R.
, p. 1625 - 1626 (2007/10/03)
Low-melting point salts, the basis of industrially relevant ionic liquids, exhibit smectic A mesophases over extended temperature ranges.
Tenside mit perfluorierten Gegenionen: Systeme mit ungewoehnlichen Eigenschaften
Angel, M.,Hoffmann, H.
, p. 153 - 174 (2007/10/02)
Conductivity measurements, kinetic investigations with relaxation techniques, static and dynamic light scattering, electric birefringence and rheological measurements were carried out on aqueous solutions of Tetradecylpyridinium-perfluorbutyrate.The measurements show that spherical micelles with an aggregation number of about 70 are formed above the critical micelle concentration (cmc).The cmc-value is about one order of magnitude lower than the cmc of Tetradecylpyridiniumchloride which is due to strong association of the hydrophobic counterions to the micelles.Above a transition concentration ct which at 25 deg C is about three times higher than the cmc, the spherical micelles begin to grow to rodlike aggregates.The lengths of these rods increase with increasing detergent concentration and reach a maximum value, when the rotational volumes of the rods begin to overlap.Above this concentration strong repulsive interaction between the aggregates takes place which gives rise to a drastic increase of the translational diffusion coefficients, to an increase of the activation energy for viscous flow and to the appearance of nonexponential decay of the transient electrical birefringence.The refractive index increments dn/dc for solutions of surfactants consisting of hydrocarbon and perfluorhydrocarbon parts were found to decrease linearly with increasing chainlength of the perfluorated part in the surfactant molecule.The electric birefringence depends strongly both on the temperature of the solutions and on the wavelength of the light used for the detection.The birefringence is negative at room temperature and the amplitude decreases also with increasing temperature and disappears above 70 deg C; surprisingly the amplitude decreases also with decreasing temperature, vanishes at 16 deg C and becomes finally positive below this temperature.An analoguous behaviour is observed at constant temperature when the wavelength of the incident light is changed; the birefringence is negative at long wavelengths, the amplitude decreases with decreasing wavelength and becomes positive below a certain wavelength.This behaviour was assumed to be due to a fortuitous compensation of the form birefringence and the intrinsic birefringence in this system.The dn/dc-values seem to play a deciding role for this compensation, because the homologuous surfactant compounds with similar dn/dc-values give the same electrooptic behaviour. - Keywords: Detergents / Hydrophobic counterions / Micelles / Electric birefringence / Refractive index increment