Facile fabrication of solvent resistant thin film composite membranes by interfacial crosslinking reaction between polyethylenimine and dibromo-p-xylene on polybenzimidazole substrates

Here, we report a novel and facile technique to fabricate solvent resistant thin film composite (TFC) membranes for organic solvent nanofiltration (OSN). It consists of two steps: (1) chemically crosslinking a polybenzimidazole (PBI) membrane with dibromo-p-xylene (DBX) and (2) exposing its top surface to polyethylenimine (PEI) and forming an ultrathin and robust PEI-DBX selective layer on top of the PBI substrate. Different from the conventional interfacial polymerization, the proposed method results in the DBX crosslinked PBI substrates with great porosity and rigidity and TFC membranes with high free volume. It also eliminates the usage of hexane and trimesoyl chloride (TMC) so that the fabrication process becomes greener, faster and more efficient. Besides, it improves the adhesion of the selective layer to the support layer significantly. The resulting membranes not only display good chemical stability in DMAc at 50 °C but also possess a molecular weight cut off (MWCO) of ~350 g mol⁻¹ with pure ethanol, acetone, tetrahydrofuran and toluene permeances of 4.5, 14, 4 and 1 L m⁻²h⁻¹bar⁻¹, respectively. Given the ease of fabrication, outstanding stability and separation performance of the resultant membranes, the newly developed technique may be applicable to design next-generation OSN membranes for chemical and pharmaceutical industries involving the separation of organic solvents at elevated temperatures.