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Updated: Apr 26, 2026

A Freeze-Thawing Method to Prepare Chitosan-Polyvinyl alcohol Hydrogels Without Crosslinking Agents and Diflunisal Release Studies
Published on: January 14, 2020
Poly(vinyl methyl ether) hydrogels at temperatures below the freezing point of water-molecular interactions and
Marcin Pastorczak1, Gustavo Dominguez-Espinosa2, Lidia Okrasa3
1Department of Molecular Physics, Lodz University of Technology, Zeromskiego 116, 90-924 Lodz, Poland ; Institute of Experimental Physics, University of Warsaw, Hoza 69, 00-681 Warsaw, Poland.
Abstract:
Water interacting with a polymer reveals a number of properties very different to bulk water. These interactions lead to the redistribution of hydrogen bonds in water. It results in modification of thermodynamic properties of water and the molecular dynamics of water. That kind of water is particularly well observable at temperatures below the freezing point of water, when the bulk water crystallizes. In this work, we determine the amount of water bound to the polymer and of the so-called pre-melting water in poly(vinyl methyl ether) hydrogels with the use of Raman spectroscopy, dielectric spectroscopy, and calorimetry. This analysis allows us to compare various physical properties of the bulk and the pre-melting water. We also postulate the molecular mechanism responsible for the pre-melting of part of water in poly(vinyl methyl ether) hydrogels. We suggest that above -60 °C, the first segmental motions of the polymer chain are activated, which trigger the process of the pre-melting.
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