Infrared and far-infrared spectroscopic studies on the structure of water in lyotropic liquid crystals

Abstract

Studies on the infrared and far-infrared spectra of water in lyotropic liquid-crystalline phases of dodecyltrimethyl ammonium chloride (and related materials) have shown the existence of at least two severely perturbed types of water molecule—both very different from bulk water. Band shifts, half-widths and relative intensities change rapidly over the concentration range, but show no discontinuities at phase boundaries (including the gel/lamellar boundary). The water molecules therefore probe only the short-range interactions between head group and counterion and do not reflect changes in long-range micellar interactions in the different mesophases. These data support the equilibrium binding model for water-surfactant interactions at polar organic interfaces and tend to refute the existence of different polarized layers. As such, they may eventually help to cast light on the nature of hydration forces between the bilayers in lamellar phases.