Enhanced antifouling and separation properties of Tröger's base polymer ultrafiltration membrane via ring-opening modification

To prepare high performance and antifouling ultrafiltration (UF) membrane, the hydrophilic polymer of intrinsic microposity (Tröger's base) (TB) polymer was designed and obtained via ring-opening of Tröger's base moieties to form secondary amine groups. Subsequently, UF membranes were prepared readily with the ring-opened TB by phase inversion method. The ring-opened TB UF membrane exhibited higher surface hydrophilicity, surface porosity and total porosity than pristine TB membrane, which was ascribed to the improved hydrophilicity of polymer due to the presence of the hydrophilic secondary amine groups. Consequently, the pure water flux of ring-opened TB membrane as high as 154 L m−2 h−1 was achieved for TB-ro-58 membrane. This value was much higher than that of pristine TB membrane. Bovine serum albumin (BSA) was chosen as a model protein foulant to evaluate the separation efficiency and antifouling properties of the TB membranes by ultrafiltration and static protein adsorption experiments. High BSA rejections were obtained for all the ring-opened TB membranes (>95%) because of their more uniform surface pore size than pristine TB membrane. The ring-opened TB membranes showed much lower static protein adsorption and less irreversible fouling than TB membrane and the antifouling property was enhanced with increase in content of secondary amine groups. Therefore, the transformation of tertiary amine groups in the backbone of TB polymer into secondary amine groups is an effective approach for the fabrication of antifouling TB UF membranes.