Evidence for a Diffuse Interfacial Region at the Dichloroethane/Water Interface

Abstract

The 1,2-dichloroethane (DCE)/water interface is important because of its suitability as an electrochemical interface between two immiscible electrolyte solutions (ITIES). An issue of particular interest is whether the interfacial region is molecularly sharp or whether the interface is comprised of a diffuse mixed interfacial region. These studies using vibrational sum-frequency spectroscopy as a probe of the structure, orientation, and bonding of interfacial water show that the interface is molecularly disordered with properties similar to a mixed phase interfacial region. It does not have the characteristics of a sharp interface that have been shown to occur at other liquid/liquid interfaces such as CCl4/H2O and alkane/H2O.

An Investigation of the Influence of Chain Length on the Interfacial Ordering of l-Lysine and l-Proline and Their Homopeptides at Hydrophobic and Hydrophilic Interfaces Studied by Sum Frequency Generation and Quartz Crystal Microbalance

“…38 The SFG spectrum of the d 8 -PS/buffer interface is quite similar to the dichloromethane/water interface that has been studied by Richmond and coworkers. 39,40 They determined that the water structure is a consequence of increased water penetration in the organic phase (something that is not likely here) 40 and general disorder at the interface.…”

Simulations of the adsorption of ionic species at polarisable liquid∣liquid interfaces

“…This picture, referred to as the modified Vervey-Niessen model (MVN) [4], has been widely used although there have been some controversies on the nature of the inner layer [14,16]. Indeed, it has been proposed that the inner layer consists of a mixed solvent layer, resulting in the overlap of the two adjacent diffuse layers [17,18].…”

“…The results obtained with these techniques appear to confirm the predictions of computer simulations. Moreover, studies using vibrational sum-frequency spectroscopy (VSFS) have demonstrated that the waterjDCE interface is molecularly disordered with properties similar to a mixed solvent interfacial region [18]. In addition, the characteristic frequencies of the capillary waves induced at the ITIES by thermal fluctuations have been measured by quasi-elastic laser scattering (QELS) [36].…”

Simple Ion Transfer at Liquid|Liquid Interfaces

“…The VSF experimental spectrum of the H 2 O-DCE interface gave a low signal in the OH stretch region with none of the distinct spectral features found in the other interfaces studied. It was thus concluded that the H 2 O-DCE interfacial region was likely to become more diffuse than other liquid|liquid interfaces, with water molecules exhibiting a random orientation at this interface [190][191][192][193].…”

“…Thus, to understand the effect of polarization on the electrical properties of the H 2 O molecules, we calculated the total dipole moments of the water molecules as a function of the z-axis of liquid| liquid interface. A few simulations with nonpolarizable models included the TIP4P water model [522,524] and OPLS CCl 4 model [190] and simulations with polarizable models used the Dang and Chang water model [521], a polarizable CCl 4 model, and a polarizable iodide [525]. One recent study of the transfer of iodide across the CCl 4 |water interface compared the free energy profile with polarizable and nonpolarizable models [74].…”