Clouding behaviour in surfactant systems.

The long-time self-diffusion coefficients of Triton X-100 micelles have been determined as a function of surfactant and electrolyte concentrations using rotating disk electrode voltammetry in conju...

Electrolyte-Induced Structural Evolution of Triton X-100 Micelles

A new recipe for surface-enhanced infrared absorption (SEIRA) active island Au films with improved adhesion in aqueous solution, low resistivity, and enhancement of the infrared (IR) absorption of about 300 was developed. The Au films prepared were utilized in studies of the ionization of self-assembled monolayers of 11-mercaptoundecanoic acid in Na2 SO4 aqueous solutions by attenuated total reflection surface-enhanced infrared absorption (ATR-SEIRA) spectroscopy. It was found that the carboxyl end groups of the self-assembled monolayer turn into carboxylate anions on going from anodic to cathodic potentials or from acidic to alkaline pH. The water molecules close to the self-assembled monolayer in acidic solutions or at anodic potentials are preferentially aligned with their dipole moments parallel to the interface. This type of alignment can be ascribed to the dipole-dipole interaction between the carboxyl groups and the water molecules. On the other hand, in alkaline solutions or at cathodic potentials the structure of water close to the self-assembled monolayer is essentially bulk-like, with randomly oriented water molecules. This observation suggests that in alkaline solutions or at cathodic potentials the charge of the carboxylate anions is almost completely compensated for by strongly adsorbed counter cations. As a result, the electric field close to the surface of the ionized self-assembled monolayer is weak and has little influence on the orientation and hydrogen bonding of the water molecules.

Attenuated total reflection surface-enhanced infrared absorption spectroscopy of carboxyl terminated self-assembled monolayers on gold.

IR spectra and hydration of short-chain polyethyleneglycols

The structure and hydrogen bonding of water in solutions containing EC at different concentrations were examined using infrared (ATR) spectroscopy. Analysis of the OH stretch vibrations of water was performed using several different techniques, and the results were compared to similar analyses found in the literature. Factor analysis and curve fitting show two concentration-dependent regions wherein the structure of water in the mixture is critically disrupted and hydrogen bonding is significantly changed.

Infrared (ATR) Study of Hydrogen Bonding in Solutions Containing Water and Ethylene Carbonate

The hydration of the short chain poly(oxyethylene)
CH
 3
(OCH
 2
CH
 2
)
 2
O
CH
 3
 (C
 1
E
 2
C
 1
) has
been studied in the range of concentrations up to 0.3 mole
fraction (m.f.) by analysing the parameters of the main
components of the water O–H stretching band at
ca. 3200 and 3400 cm
 -1
. Two interesting
regions of enhancement of the hydrogen bond network in the
solution characterize different hydration structures. In the
first at ca. 0.03 m.f., the coordination of the
water network around the
C
 1
E
 2
C
 1
 molecules has a
local maximum owing to hydrogen bonding at the sites of the
ether oxygens from one side, and the hydrophobic hydration
around the methylene groups and the CH
 3
 end
groups, from the other. The increased local order in the
hydration structure is a consequence of the favourable
incorporation of the oxyethylene groups of
C
 1
E
 2
C
 1
 molecules with
gauche conformation in the water network because of
their similar O···O distances. In
contrast, the second type of hydration structure at
ca. 0.11 m.f. can be explained by the build up of
the most compact homogeneous hydrogen bond network in which
C
 1
E
 2
C
 1
 molecules are
interconnected with direct hydrogen bonds to the most water
molecules possible and the effect of hydrophobic hydration
is diminished. Above 0.11 m.f. the hydrogen bond network in
the system is gradually destroyed.

Nicolai Goutev

Papers

Hydration of a short chain poly(oxyethylene)(C1E2C1) studied byanalysis of the O—H Raman band

Hydration structure of 1,2-dimethoxyethane (C1E1C1): OH Raman band studies