State of water in chitosan /tripolyphosphate polyelektrolyte complex membranes for pervaportation

Polyelectrolyte complexes (PECs) are known as new interesting membrane materials applicable in industry, medicine and pharmacy. In this work PEC membranes from chitosan (Ch) and pentasodium tripolyphosphate (TPP) designed for pervaporation w'ere prepared by dipping Ch membranes in TPP solution. The PEC formation between Ch and TPP was confirmed by FTIR spectroscopy. Various amounts of w'ater were added into the dry ChATPP hydrogels to cause them to swell, and the amounts of water in various states were determined by the DSC ice-melting technique. Three types of water in hydrogel membranes w'ere identified: non-freezing bound water, freezing bound water, and freezing free w'ater. States of water in Ch/TPP and Ch membranes were compared and the effect of ionic crosslinking on the non-freezing water content was discussed.