Influence of the salt concentration on the properties of salt-free polyelectrolyte complex membranes

Abstract

Polyelectrolyte complexes (PECs) prepared by solution mixing of cationic poly(diallyldimethylammonium chloride) and anionic poly(sodium 4-styrene sulfonate) with various NaCl content are processed into films. Salt-free (SF-PEC) membranes are produced by rinsing the PEC in water overnight. The main finding of this paper is that SF-PEC films have different properties depending on the NaCl concentration used during the processing step. Dynamic mechanical analysis measurement confirms that hydrated SF-PEC film processed from higher salt content has a higher modulus than when processed without salt and the glass transition temperature appears to shift to higher values. Processing the PECs films in the presence of salt also has an interesting effect on their shape memory characteristics. SF-PEC films prepared with high-salt concentration are shown to maintain a programmed temporary shape better than materials prepared with low salt, while recovery is possible within a short period of time when immersed in hot water.