Abstract
Polypyrrole/acetylcellulose composite membranes, the solute-separation property of which is controllable, were prepared by electrochemical polymerization of pyrrole in a ultrafiltration membrane of acetylcellulose. The polymerization was carried out with two supporting electrolytes (NaClO4 and sodium p-toluenesulfonate) under a galvanostatic condition. The difference of the supporting electrolytes influenced the solute-separation property of the formed composite membranes.
The separation property of the membranes was evaluated by the rejection of various molecular weights of polyethylene glycol as model solutes. The composite membranes separated the solutes with the molecular weight from a few hundreds to a few thousands. They changed their molecular weight cut-off by electrochemical doping and dedoping of electrolyte anions (dopants) to the polypyrrole component. In the composite membranes, the pores in the active layer of the acetylcellulose membrane component were likely to be filled with polypyrrole molecules. It was considered that the changes of the molecular weight cut-off were due to blockage of the pores by incorporation of the dopant anions into the polypyrrole molecules.
The composite membranes also changed finely the values of the solute rejection by adjusting the applied doping potential when the dopant anion with suitable molecular weight was selected (for example, 1-naphtalenesulfonate anion). Therefore, the composite membranes in the present study were recognized as the functional separation membranes, the solute-separation property of which is externally controllable.
