Hydration/Dehydration Behavior of Hydroxyethyl Cellulose Ether in Aqueous Solution

Abstract

Hydroxyethyl cellulose (HeC) maintains high water solubility over a wide temperature range even in a high temperature region where other nonionic chemically modified cellulose ethers, such as methyl cellulose (MC) and hydroxypropylmethyl cellulose (HpMC), demonstrate cloud points. In order to clarify the reason for the high solubility of HeC, the temperature dependence of the hydration number per glucopyranose unit, nH, for the HeC samples was examined by using extremely high frequency dielectric spectrum measuring techniques up to 50 GHz over a temperature range from 10 to 70 °C. HeC samples with a molar substitution number (MS) per glucopyranose unit by hydroxyethyl groups ranging from 1.3 to 3.6 were examined in this study. All HeC samples dissolve into water over the examined temperature range and did not show their cloud points. The value of nH for the HeC sample possessing the MS of 1.3 was 14 at 20 °C and decreased gently with increasing temperature and declined to 10 at 70 °C. The nH values of the HeC samples are substantially larger than the minimum critical nH value of ca. 5 necessary to be dissolved into water for cellulose ethers such as MC and HpMC, even in a high temperature range. Then, the HeC molecules possess water solubility over the wide temperature range. The temperature dependence of nH for the HeC samples and triethyleneglycol, which is a model compound for substitution groups of HeC, is gentle and they are similar to each other. This observation strongly suggests that the hydration/dehydration behavior of the HeC samples was essentially controlled by that of their substitution groups.

Hydrogen-Bond Configurations of Hydration Water around Glycerol Investigated by HOH Bending and OH Stretching Analysis

“…The complex permittivity, ε̃( v ) = ε′( v ) – iε″( v ), from 50 MHz to 45 GHz was determined by impedance and vector network analyzer (VNA) measurements at 25 °C with temperature controlled by a Peltier element. , Impedance measurements were conducted from 50 to 500 MHz with an RF LCR meter 4287A (Agilent Technologies) calibrated in the open (air), short (a 0.5 mm thick gold plate), and load (pure water for ≤50 mol % glycerol, and pure methanol for >60 mol %). Measurements over 500 MHz and 45 GHz were performed with a VNA system N5230 equipped with a dielectric probe kit 8507E and an ECal module 4693A (Agilent Technologies) after performing three-point calibration.…”

Solid and Semisolid Innovative Formulations Containing Miconazole-Loaded Solid Lipid Microparticles to Promote Drug Entrapment into the Buccal Mucosa

“…To prepare the SLMs-loaded gel, hydroxyethylcellulose (HEC), trehalose and PVP-K90 were chosen as excipients in order to obtain a homogenous, transparent and bubble-free gel in which to incorporate MCZ-loaded SLMs. HEC is a gelling and thickening agent derived from cellulose and widely used in the cosmetic and pharmaceutical fields [ 31 ]. Polyvinylpyrrolidone (PVP) is a biocompatible, biodegradable, water-soluble polymer often used to prepare formulations with strong mucoadhesive properties [ 32 , 33 ].…”

A Review on the Design and Hydration Properties of Natural Polymer-Based Hydrogels

“…However, cellulose exhibits excellent properties (e.g., mechanical strength, biodegradability, hydrophilicity, and biocompatibility) that are responsible for its extensive use in the fabrication of hydrogel materials with diverse applications in biomedicine and pharmaceuticals. Many kinds of chemically-modified cellulose, such as methyl-, hydroxypropyl-, hydroxyethyl-, and hydroxymethyl-cellulose, exist that are water soluble [ 104 ]. Cellulose-based hydrogels have been formed, utilizing native cellulose (and its derivatives) in homogenous media (e.g., LiCl and ionic liquids) to solubilize cellulose, and in heterogenous media where cellulose fibers are used to modify the mechanical properties of hydrogels [ 28 ].…”