Preparation of chemically attached polyamide thin film membrane using different diamines: separation and computational investigation

The research in this work exploits different diamines to crosslink chemically a polyamide thin layer to a PES/PI blend substrate through a new procedure. The main goal was to prepare innovative new polyamide (PA) thin film membranes without using an aqueous phase (unlike conventional methods to fabricate the PA thin layers) and to try chemically binding the formed thin layer to the substrate. Different diamines, namely EDA (ethylenediamine), PIP (piperazine), and PPD (para-phenylenediamine) were used as monomers and crosslinkers to open the imide rings and to provide the desired sites for better attaching of the generated thin layers to the support. Computational methods were used to assess the reaction mechanism and strength of the formed bindings. Chemical and physical properties of the modified and unmodified membranes were measured by SEM, AFM, FTIR-ATR, TGA, and contact angle test. The IR spectra and the measured performance indicated that the thin layer was successfully formed. The rejection capability of the membranes against Na₂SO₄ increased from near 2% to about 85% in the TMC-EDA modified membrane. Antifouling properties of the obtained membranes were measured by BSA solution and E. coli bacteria, showing a flux recovery ratio near 97% and favorable antibacterial properties for the TMC-EDA modified membrane. The calculation results also proved that the EDA was the best crosslinker and monomer for this purpose, and accordingly, the TMC-EDA modified membrane showed the desired binding strength.