Hydration Behavior of Poly(ethylene oxide)s in Aqueous Solution As Studied by Near-Infrared Spectroscopic Techniques

Abstract

Near-infrared (NIR) absorption measurements over a wavenumber range from 4000 to 12000 cm(-1) were used to investigate hydration behavior of poly(ethylene oxide)s bearing molar masses of 3 × 10(3) (PEO3) and 20 × 10(3) (PEO20) in aqueous solution at a dilute regime. NIR absorption spectra for solutions were perfectly decomposed into three components: bulk water, PEOs, and hydrated water to PEOs. While amounts of each component were proportional to the concentrations of PEOs (cEO), the wavenumber dependence of each spectrum was independent of cEO and also the molar masses of PEOs. A newly determined NIR absorption spectrum of hydrated water molecules to PEOs found in a wavenumber range from 5500 to 7500 cm(-1) was well described with the summation of two Gaussian-type vibration modes possessing the same magnitude, which were observed at different wavenumbers of 6480 and 6910 cm(-1), respectively. Each mode was assigned to O-H stretching first overtone of water molecules hydrated directly to ether oxygen atoms (6480 cm(-1)) and water oxygen atoms (6910 cm(-1)) belonging to the secondary hydration layer.

Self-assemblies of pluronic micelles in partitioning of anticancer drugs and effectiveness of this system towards target protein

“…The rise in temperature leads to dehydration of PEO units thereby increases the hydrophobic character of the polymer chain. 31 Thus these molecules can assemble into micelles at a relatively lower concentration at higher temperatures.…”

Dangling OH Vibrations of Water Molecules in Aqueous Solutions of Aprotic Polar Compounds Observed in the Near-Infrared Regime

“…The frequency dependency of the ΔABS* × c −1 spectrum seen in Figure 3b is considerably different from that of aqueous solutions of poly(ethylene oxide)s and crown ether samples consisting of hydrophilic ether groups, which showed a strong major peak at 6900 cm −1 and another broad one at 6500 cm −1 assigned to the first overtone of O−H stretching, 2ν OH , hydrogen boned to oxygen atoms of other water molecules and those of solute ether groups. 26 According to the previous study using dielectric spectroscopic technique, MeNO 2 molecules behave as a hydroneutral compound and have no hydrated water molecules possessing hydration lifetime longer than relaxation time, τ W , of water molecules in the pure liquid state. 26 Then, water molecules affected by the MeNO 2 do not have strong interaction to form a hydrogen bond leading to stable hydration but a weak dipolar interaction between the dangling OH group and a polar −NO 2 group bearing a large dipole moment of 3.4 D. The presence of the dangling OH has been clearly confirmed in aqueous solutions of dipolar solutes such as MeCN and acetone based on the result of RS measurements demonstrating additional fundamental O−H stretching mode at 3450−3500 cm −1 , meaning the presence of dangling OH around MeCN.…”

“…The reason for differences in reported n H values obtained by distinct techniques is a difference in physical meaning of n H depending on the techniques. 26 Dielectric spectroscopic techniques to precisely determine the hydration numbers of solute molecules dissolved in water are performed in an extremely high frequency range up to, for example, 50 GHz. 9−15 Because the dielectric relaxation strength of free-water molecules in aqueous solutions is exactly evaluable in the frequency range, the amount of water molecules hydrated to solute molecules can be precisely determined.…”

Double‐network polyvinyl alcohol composite hydrogel with self‐healing and low friction

“…PEG is a polymer composed of polar molecules containing hydroxyl groups ( OH), which after mixing cross-link through hydrogen bonding to each other to form a composite gel with a three-dimensional network structure (bottom of Figure 12). 54,55 The PVA in the composite gel has a multi-microporous structure, and the hydrophilic-group ether-bond ( O ) within the PEG molecule forms a hydration layer during the dissolution process, thereby ensuring that the PEG is tightly wrapped by water molecules. 56 In the friction process, the PEG stored in the pores of the PVA owing to the effect of external pressure is constantly extruded in the two friction pairs of a relative-sliding-contact surface owing to the effect of external pressure to form a boundary lubrication film.…”