Synthesis of polyamide thin-film nanocomposite membranes using surface modified imogolite nanotubes

Nanocomposite membranes were synthesized using unmodified and surface modified imogolite nanotubes. Membranes were through interfacial polymerization of polyamide onto polyacrylonitrile (PAN) macroporous supports. Surface modification was done using two different polymers: polyvinylpyrrolidone (PVP) and polydimethylsiloxane (PDMS). These polymers were selected to improve nanotube dispersion in chloroform and n-hexane solvents which were used during membrane synthesis. The structural and surface-chemical properties of the nanotubes and the synthesized thin-films were characterized and correlated with membrane performance. Surface modification resulted in an increased mass loading of nanotubes into the polyamide thin-films. This corresponded to an increase in water permeability, going from 1 mg/g to 2.5 mg/g as the mass loading increased from 1.47 × 10-12 m/Pa s to 3.59 × 10-12 m/Pa s. Increases in water permeability were attributed to increases of the pore size from 3.967 to 4.357 nm within the membrane due to the interior space of the nanotubes and to changes in the cross-linking density surrounding the nanotube within the thin-film.