Preparation of Ultrathin Self-Standing Polyelectrolyte Multilayer Membranes at Physiological Conditions Using pH-Responsive Film Segments as Sacrificial Layers

A new system to obtain ultrathin self-standing polyelectrolyte multilayer membranes at physiological conditions is introduced. On the surface of a substrate, a hybrid film structure composed of two compartments, (1) a pH-responsive film segment formed via hydrogen bonds and (2) a polyelectrolyte multilayer film on top of 1, was assembled. The pH-responsive polymer multilayer segments disintegrate at a neutral pH and release self-standing polyelectrolyte multilayer films. The obtained self-supporting polyelectrolyte multilayer membranes had thicknesses of 55 to several hundred nanometers and areas of a few square centimeters, approximately. The preparation method introduced here avoids harsh release conditions and thus broadens the choice of materials that can be incorporated into the self-standing film.