pH-sensitive characteristics of poly(acrylic acid)-functionalized anodic aluminum oxide (AAO) membranes

A simplified method to prepare pore-filled pH-responsive membranes was provided by using anodic aluminum oxide (AAO) membrane as supported matrix. To introduce reactive groups for grafting weak polyelectrolyte, silica–AAO composite membrane was prepared by depositing silica onto the AAO membrane through sol–gel method. The obtained composite membrane keeps the ideal pore structures of the original AAO membrane. Poly(acrylic acid) as responsive polymer was grafted onto the silica–AAO composite membranes by activating with 3-glycidoxypropyl trimethoxysilane. The obtained pH-responsive membranes showed evident pH-sensitivity, and the pH-valve effect was observed at the pH between 3 and 5. Electrochemical impedance spectroscopy demonstrates the membrane resistance increases from 4.3 × 105 Ω cm2 at pH 2 to 1.3 × 106 Ω cm2 at pH 6.