Contents lists available at ScienceDirect Journal of Membrane Science journal homepage: www.elsevier.com/locate/memsci Crosslinked poly(ether block amide) composite membranes for organic solvent nanofiltration applications Jamaliah Aburabie, Klaus-Viktor Peinemann ⁎ Advanced Membranes and Porous Materials Centre, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Kingdom of Saudi Arabia ARTICLE INFO Keywords: Pebax ® Poly(ether block amide) Organic solvent nanofiltration Graphene oxide ABSTRACT Poly(ether block amide) – Pebax ® – based membranes are well described for gas separation applications. But only a few publications exist for their application in pressure driven liquid applications like ultrafiltration and nanofiltration. Here we use the commercially available Pebax ® 1657 for the preparation of membranes for the filtration of organic solvents. Porous polyacrylonitrile membranes were coated with Pebax ® 1657 which was then crosslinked. Toluene diisocyanate (TDI) was used as a crosslinker agent for the coating. Reaction time and crosslinker concentration were optimized for the aimed application. The Pebax ® coating and the impact of the TDI on the resulting crosslinked membranes were investigated by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). SEM analysis shows a uniform thin coating of the PEBAX that covers the pores of the PAN membranes. FTIR and DSC analysis confirm the crosslinking reaction. Crosslinked Pebax ® membranes show high stability toward ethanol propanol, acetone and even dimethylformamide (DMF). In the case of DMF applications, the standard PAN was replaced by crosslinked PAN developed in our laboratory. In order to increase the membranes permeances, graphene oxide (GO) nanosheets were incorporated in the Pebax ® coating. These GO containing membranes showed strongly increased permeances for selected solvents. 1. Introduction Polymeric membranes found their way into conventional industrial separation processes, such as gas separation and water purification due to their mechanical robustness, structural diversity and relatively low fabrication cost [1,2]. In the last few years, the interest in developing polymeric membranes for solvent resistant nanofiltration is growing. Solvent-stable nanofiltration membranes are rapidly gaining attention due to their potential to replace distillation in various industries, such as petrochemistry, food and pharmaceutical industries, which involve the use of a large amount of aggressive polar aprotic solvents [3–6]. Organic solvent nanofiltration membranes require high resistivity towards solvents and a molecular weight cut off (MWCO) of 200– 1000 g/mol. Easy processability is important to facilitate industrial manufacture and commercialization. The most studied polymer for these applications is polyimide (PI). This polymer exhibits good chemical stability towards some solvents and its resistivity could further be improved by chemical crosslinking. The Livingstone group achieved high fluxes and outstanding rejection performances using thin film composite membranes prepared on crosslinked PI supports [7– 16]. The search for further polymers that can be implemented in this area is still going on and recently many polymers found their way into OSN such as polythiosemicarbazide (PTSC), polybenzimidazole (PBI) and other polyazoles [17–19]. Commercially available poly(ether block amide) resins are known under the trademark Pebax ® . They are thermoplastic elastomer block copolymers, which combine linear chains of rigid polyamide segments interspaced with flexible polyether segments. Through the proper combination of polyether and polyamide segments a wide range of grades are available. Fig. 1 shows the general structure of any Pebax ® polymer grade. Polyamide (PA) represents the crystalline polyamide “hard segment” that promotes mechanical stability and it can be nylon- 6 or nylon-12. Polyether (PE) represents the amorphous polyether “soft segment” that provides good solvent affinity such as poly(ethylene oxide) or poly(tetramethylene oxide). Pebax ® membranes have been investigated in ultrafiltration, nano- filtration, pervaporation, solvent filtration and gas separation pro- cesses. The first use of Pebax ® composite membranes for aqueous ultrafiltration was reported by Nunes et al. in 1995, where dense hydrophilic coatings were applied on PVDF support [20]. http://dx.doi.org/10.1016/j.memsci.2016.09.027 Received 11 June 2016; Received in revised form 4 August 2016; Accepted 17 September 2016 ⁎ Corresponding author. E-mail address: klausviktor.peinemann@kaust.edu.sa (K.-V. Peinemann). Journal of Membrane Science 523 (2017) 264–272 0376-7388/ © 2016 Elsevier B.V. All rights reserved. Available online 28 September 2016 crossmark