Stepwise synthesis of oligoamide coating on a porous support: Fabrication of a membrane with controllable transport properties

Porous polymeric membranes are widely used in potable water purification, wastewater treatment, the food and the pharmaceutical industries, and haemodialysis. However, producing specialized membranes with diverse transport properties is challenging. A method for fabricating membranes with controllable transport properties is described here by stepwise synthesis of aromatic oligoamide on a porous polymeric support. The use of aromatic oligoamide affords good water permeance due to its hydrophilic character. Alternate couplings of trimesoyl chloride and meta-phenylenediamine yielded an oligoamide dendrimer that was covalently bonded to the support. The water permeance and molecular weight cutoff (MWCO) of the synthesized membranes were controlled (with values of 4.6 to 543 L·m−2·h−1·bar−1 and 22.6 to 332 kDa, respectively) by adjusting the number of oligoamide synthesis cycles in the range of 2.5–20.5. The oligoamide membrane with 5.5 synthetic cycles showed a high rejection of the negatively charged rose bengal dye (95% rejection) with high flux (126.4 ± 4.2 L·m−2·h−1 at 5.2 bar), as compared with other membranes reported in the literature. The fabricated membranes are potentially highly useful for the separation of macromolecules with specific ranges of molecular weight, for industrial separations that require membranes with tunable MWCO ranges, or for the separation of charged macromolecules.