Bio-Inspired Robust Membranes Nanoengineered from Interpenetrating Polymer Networks of Polybenzimidazole/Polydopamine

Marine mussel inspired polydopamine (PDA) has been receiving increased attention due to its good thermal and chemical stability as well as strong adhesion on most materials. In this work, high performance nanofiltration membranes based on interpenetrating polymer networks (IPN) incorporating PDA and polybenzimidazole (PBI) were developed for organic solvent nanofiltration (OSN). Generally, in order to obtain solvent stability, polymers need to be covalently crosslinked under harsh conditions, which inevitably leads to losses in permeability and mechanical flexibility. Surprisingly, by in situ polymerization of dopamine within a PBI support, excellent solvent resistance and permeance of polar aprotic solvents were obtained without covalent crosslinking of the PBI backbone due to the formation of an IPN. The molecular weight cut-off (MWCO) and permeance of the membranes can be fine-tuned by changing the polymerisation time. Robust membrane performance was achieved in conventional and emerging green polar aprotic solvents (PAS) in a wide temperature range covering –10 °C to +100 °C. It was successfully demonstrated that the in situ polymerization of PDA — creating an IPN — can provide a simple and green alternative to covalent crosslinking of membranes. To elucidate the nature of the solvent stability, a detailed analysis was performed that revealed that physical entanglement along with strong secondary interaction synergistically enable solvent resistance with as low as 1–3% PDA content.