Through the complexation of two anionic polysaccharide blends composed of sodium alginate and carrageenan with divalent calcium ions, polyelectrolyte complex membranes were prepared. The effects of annealing on the structure of the polyelectrolyte complex membranes and on their performance at removing water from a methanol mixture were investigated and discussed. The annealed membranes exhibited a change in their crystallinity. The change was due to a rearrangement of polymer chains, which was induced by a deformation of the chelate structure and intra-molecular or intermolecular interactions between the polysaccharides. Because of the effects of annealing on the resulting membranes, water components almost penetrated the membranes to the permeate side in the vapor permeation process. Moreover, the membrane performances were gradually enhanced as the operating temperature increased. (c) 2006 Wiley Periodicals, Inc.