Design and Prepare Hyperbranched Polymer Composite Membrane from an Industrial Material-Boltorn W3000
Lin Wang, Naixin Wang*, Tong Wu, Yue Zhang, Cui Zhao, Shulan Ji*
Beijing Key Laboratory for Green Catalysis and Separation and Department of Chemistry and Chemical Engineering, Beijing University of Technology, Beijing 100124, P. R. China.
Nowadays, hyperbranched polymers (HBPs) have been widely investigated in membrane fabrication process, due to its unique physical and chemical properties, such as low viscosity, small molecular weight and abounding of active terminated groups [1-3]. Herein, a commercially available HBP, Boltorn W3000, was used as the membrane material, which contains hyperbranched polyester as the core, grafted by hydrophobic fatty acid chains (see Fig. 1) . On the basis of the distinctive molecular structure, two simple but effective approaches were utilized to obtain composite membranes for nanofiltration (NF) and pervaporation (PV).
Firstly, NF membranes were prepared on the PAN flat substrate from aqueous W3000 emulsion via a novel one-step self-assembly method (see Fig. 2). The obtained membrane presents an excellent performance in dye desalination. The dye (methyl blue) and salt retentions can reach 97.0% and less than 12.0%, respectively. Meanwhile, the flux of the composite membrane for dye desalination can reach 55.0 L∙m-2∙h-1 under the operation pressure of 0.5 MPa. In addition, the composite membrane maintained stable separation performance under different operating conditions and a long-time running test.
Beside, a simple self-crosslinking strategy was employed to prepare composite membranes for PV separation of toluene/n-heptane mixtures. After thermal crosslinking, the hydroxyl and carboxyl groups on Boltorn W3000 molecules could react at intramolecular and intermolecular to form a stable dense layer. The separation factor and permeation flux of the "pore-filling" membrane could respectively reach 5.1 and 63.1 g/(m2h) (40 oC). With respect to the "non-pore-filling" membrane, the composite membrane with "pore-filling" structure performed considerably stable separation properties.
Moreover, as the materials are commercially available and the fabrication process are facile, the membrane obtained via these two approaches would have great potential in industrial application.
Keywords: Hyperbranched polymer; Self-emulsify; Self-crosslinking; Nanofiltration; Pervaporation.
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Fig. 1 Schematic representation of the amphiphilic HBP Boltorn W3000 molecular structure.
Fig. 2 Schematic illustration of the preparation process of cross-linked PAN/Boltorn composite membrane from aqueous emulsion.
Fig. 3 Schematic illustration of the preparation process of Boltorn W3000 composite membrane with simple self-crosslinking strategy.