Impact of the Alkali Metals Ions on the Dielectric Relaxation and Phase Transitions in Water Solutions of the Hydroxypropylcellulose

Abstract

The properties of water solutions of hydroxypropylcellulose (HPC) of different concentrations with added salts of the first group alkali metals (chlorides of Li, Na, K, Rb, and Cs) with the physiological saline concentration of 154 mmol L−1 were studied using electroconductivity, turbidimetry, densitometry, viscometry, dynamic light scattering, dielectric, and luminescence spectroscopy methods. All HPC-water-salt systems were shown to exhibit lower critical solution temperature (LCST) at temperatures between 40 and 50 °C. Adding ions to the HPC-water solutions leads to the decrease in LCST and the appearance of agglomeration of nanoparticles at temperatures above LCST. At low temperatures, when the solutions are solid, the presence of ions in the solution shifts the dielectric relaxation to lower temperatures. This shift negatively correlates with the mass of ions in the solution. The ions are shown to affect several physical properties in both solid and liquid states similarly. Such similarity is attributed to the ability of ions to affect the structure of the hydrate shell and the close surroundings of HPC, as well as to the change of this structure with increasing temperature. The observed effects appear to be macroscopic attributes (markers) of the change in the structure and its kinetic properties due to impurities or thermal motion.