Controlled Nanoconfinement of Polyimide Networks in Mesoporous γ-Alumina Membranes for the Molecular Separation of Organic Dyes

Polyimide networks are key in the development of stable, resilient, and efficient membranes for separation applications under demanding conditions. To this aim, the controlled design of the network's nanostructure and its properties are needed. However, such control remains a challenge with currently available synthesis methods. Here, we present a simple nanofabrication approach that allows the controlled nanoconfinement, growth, and covalent attachment of polyimide (PI) networks inside the mesopores of gamma-alumina layers. The attachment of the PI network on the gamma-alumina layer was initiated via different prefunctionalization steps that play a pivotal role in inducing the in situ polymerization reaction at the pore entrance and/or at the inner pore surface. The nanoconfinement was found to be limited to the 1.5 mu m-thick gamma-alumina supporting layer at maximum, and the resulting hybrid PI/ceramic membranes showed stable performance in a variety of solvents. These PI/ceramic membranes were found to be very efficient in the challenging separation of small organic dye molecules such as Rhodamine B (479 g mol(-1)) from toxic solvents such as dimethylformamide or dioxane. Therefore, this technique opens up possibilities for a multitude of separations. Moreover, the PI synthesis approach can be applied to other applications that also rely on porosity and stability control, such as for advanced insulation and anticorrosion.

Automated summary

Polyimide networks are crucial for developing stable, resilient, and efficient membranes for separation applications under demanding conditions. A simple nanofabrication approach was presented to achieve controlled nanoconfinement, growth, and attachment of PI networks inside the mesopores of gamma-alumina layers. These hybrid PI/ceramic membranes showed stable performance in various solvents, making them highly efficient in challenging separations of small organic dye molecules. This technique opens up possibilities for a multitude of separations and other applications requiring porosity and stability control.