Towards fully epoxy-based thin film composite membranes for solvent-resistant and solvent-tolerant nanofiltration

Epoxy curing is a versatile chemistry that can be applied in membrane preparation, both via phase inversion and interfacial polymerization. Here, fully epoxy-based TFC membranes are demonstrated for the first time and tested for solvent-tolerant nanofiltration (STNF) applications. First, UF membranes with a retention for bovine serum albumin (BSA, ∼66000 g mol−1) of ∼40% and a water permeance of 171 L m−2 h−1 bar−1 were prepared via phase inversion by pre-curing epoxide resins (EPON™ resin 1009F and EPON™ resin SU-8) with 1,6-hexanediamine (HDA) prior to phase inversion in water. Subsequently, selective top layers were synthesized on these supports layers via interfacial polymerization (IP) or interfacial initiation of polymerization (IIP) of the same epoxy resins, resulting in a thin selective top layer of the same material. By using different amines, different epoxide ring-opening polymerizations (ROP) could be targeted. These TFC membranes were then tested for use in water-solvent mixtures and achieved a 92.8% methyl orange (MO, 327 g mol−1) retention and a permeance of 0.21 L m−2 h−1 bar−1 in a 20/80 DMF/water feed solution. Cured epoxy chemistry is known for its excellent chemical stability, making these membranes suitable for a wide variety of solvent-resistant NF (SRNF) and STNF applications.