Hybrid Polymer−Silicon Proton Conducting Membranes via a Pore-Filling Surface-Initiated Polymerization Approach

An alternative approach for the creation of proton conducting platforms is presented. The methodology is based on the so-called "pore-filling concept", which relies on the filling of porous matrices with polyelectrolytes to obtain proton conducting platforms with high dimensional stability. Polymer-silicon composite membranes, with well-defined polyelectrolyte microdomains oriented normal to the plane of the membrane, were prepared using photoelectrochemically etched silicon as a microstructured scaffold. Ordered two-dimensional macroporous silicon structures were rendered proton conducting by filling the micropores via a surface-initiated atom transfer radical polymerization process. The morphological aspects, chemical stability, and performance of the hybrid assemblies were characterized by a set of techniques including scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, nuclear magnetic resonance and impedance spectroscopy, among others. The fabricated silicon-poly(sodium 2-acrylamide-2-methylpropane sulfonate) hybrid membranes displayed proton conductivities in the range of 1x10(-2) S/cm. This work illustrates the potential of hybrid polymer-silicon composite membranes synthesized by pore-filling surface-initiated polymerization to create proton conducting platforms in a simple and straightforward manner. Versatility and relative ease of preparation are two key aspects that make this approach an attractive alternative for the molecular design and preparation of proton conducting systems.