Raman spectroscopy was used to investigate molecular interactions and structure of water in PVME hydrogels of various crosslinking degrees. Analysis of polymer nu(CH3) and nu(CH2) stretching vibrations has allowed to monitor the changes of hydrophilic and hydrophobic polymer-water interactions in a course of water deswelling and volume phase transition. Formation of water-polymer hydrogen bonds has appeared to influence directly supramolecular structure of the absorbed water. It was found that the polymer network density determines an availability of the hydrophilic sites to water molecules and also influences the kinetics of volume phase transition of the hydrogels. Activation energy of the volume phase transition in the investigated systems was estimated to be ca.88 kJ/mol. (C) 2009 Elsevier Ltd. All rights reserved.