Solution-Processed Ultrathin Aluminosilicate Nanotube-Poly(vinyl alcohol) Composite Membranes with Partial Alignment of Nanotubes

The fabrication of ultrathin (300 nm) aluminosilicate nanotube-poly(vinyl alcohol) composite membranes with partial vertical alignment of the nanotubes (up to 33%), by solution-casting methods on porous polymeric substrates, is reported. A high loading (up to 60 vol%) of nanotubes is achieved. A comprehensive microstructural characterization of the membranes is performed by a combination of SEM, TEM, grazing-incidence wide-angle X-ray scattering measurements, and simulations. This investigation shows that the nanotubes are individually dispersed and partially aligned in the polymeric matrix by the use of appropriate matrix and substrate materials. Permeation measurements of gas probe molecules (CO2 and CH4) on two different types of membranes, one containing bare nanotubes and the other containing amine-functionalized nanotubes, also support the proposed microstructure of the thin nanocomposite membranes.