Coupled-PDMS grafted mesoporous γ-alumina membranes for solvent nanofiltration

• Grafting of mesoporous γ-alumina with hydride terminated polydimethylsiloxane is described.
• Tetrakis(vinyldimethylsiloxy)silane is used to couple the grafted moiety.
• A polymer network inside the ceramic pores is formed.
• The use of coupling agents results in a higher selectivity at the cost of solvent permeability.

In this paper grafting of mesoporous γ-alumina membranes with hydride terminated polydimethylsiloxane is described. Vinyltriethoxysilane is used as linking agent and tetrakis(vinyldimethylsiloxy)silane as a coupling agent, to create a dense network structure that is grafted in the ceramic pores. Grafting performance of the organic moieties on γ-alumina powders was analyzed by FTIR and TGA. The results indicate that grafting reactions were successfully carried out. Contact angle analysis on the grafted membranes showed that grafting occurs on the γ-alumina layer and that the resulting membrane surface had a water contact angle of 108°. From permeability and rejection tests using Sudan Black in toluene, ethyl acetate or isopropanol, the use of a coupling agent was found to result in a more dense network structure grafted in the gamma alumina pores. This resulted in a higher rejection for nanofiltration of solvents but at the cost of a lower solvent permeability, when compared with PDMS-grafted alumina membranes where no coupling of PDMS was applied.