Sequential Infiltration Synthesis of Al2O3 in Polyethersulfone Membranes

We report the sequential infiltration synthesis (SIS) of aluminum oxide (Al2O3) into polyethersulfone (PES) ultrafiltration (UF) membranes to form hybrid nanocomposites. SIS relies on chemical interactions between precursor vapors and polymer functional groups, and enables nucleation and growth of inorganic materials to controlled depth. Using in situ Fourier-transform infrared spectroscopy and ellipsometry measurements, we demonstrate that trimethylaluminum associates with the sulfonyl groups in PES, extending the library of SIS-modified polymer nanocomposites to a previously undescribed polymer system and new application space: PES UF membranes. Depth-profiled x-ray photoelectron spectroscopy showed that the trimethylaluminum purge time dictates the extent of Al2O3 infiltration. Energy dispersive spectroscopy revealed the differences between SIS and atomic layer deposition in the membranes. This work demonstrates the viability of SIS to access the entire macroporous volume of PES UF membranes.