Influence of hydrophobic block length and ionic liquid on the performance of multiblock poly (arylene ether) proton exchange membrane Swati Awasthi, Vaishnav Kiran, Bharti Gaur * Department of Chemistry, National Institute of Technology, Hamirpur 177005, India article info Article history: Received 20 December 2016 Received in revised form 2 March 2017 Accepted 3 March 2017 Available online xxx Keywords: Multiblock copolymers Proton exchange membrane Imidazole ionic liquid Proton conductivity Morphology abstract The present article includes the synthesis of nanophase-separated poly (arylene ether) multiblock copolymers. A series of poly (arylene ether sulfone) hydrophobic oligomers consisting of bisphenol-A groups were reacted with a disulfonated poly (arylene ether ketone) hydrophilic oligomer containing 4, 4 0 - bis (4-hydroxyphenyl) valeric acid moieties to prepare multiblock copolymers. The synthesized oligomers and block copolymers were characterized by using FT-IR, 1 H NMR spectra and Gel Permeation Chromatography. The membranes obtained by solution casting method exhibited good dimensional and thermal stability. The increase in hydrophobic block length reduced the water uptake and methanol permeability of the membranes. The complexation of multiblock copolymer with ionic liquid (1-butyl-3-methyl-imidazolium tetrafluoroborate) resulted into novel hybrid mem- branes. These showed enhanced proton conductivity without affecting the mechanical stability. The Fenton's test revealed that the hybrid multiblock membranes were stable towards radical oxidation. The hydrophobic-hydrophilic phase separation was character- ized by using tapping mode Atomic Force Microscopy (AFM). The hybrid membranes showed better fuel cell performance than that of pristine membrane. © 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved. Introduction Ever growing energy demand, depleting fossil fuel reserves and growing environmental concerns have led to accelerated development of alternative energy conversion technology. Proton exchange membrane fuel cells (PEMFCs) are one of the most promising automotive and stationary power sources for the future since these use hydrogen as the fuel and produce water as the by-product [1e3]. Direct methanol fuel cells (DMFCs) use dilute methanol as fuel and are portable power version of the PEMFCs. The critical component of the PEMFCs as well as DMFCs is the polymer electrolyte/proton exchange membrane (PEMs). The downsides of the state-of-the-art Nafion PEMs like high cost (major factor), environmental in- compatibility associated with its disposal and decrease in conductivity along with high fuel crossover at higher tem- perature (>100  C) have stimulated the interest in hydrocar- bon based polymeric materials as PEMs [4,5]. In the recent years, sulfonated hydrocarbon based aromatic polymer membranes, including polybenzimidazole [PBI], poly (arylene ether nitrile) [PAEN], poly (arylene ether ether ketone) [PEEK], poly (arylene ether sulfone) [PES], poly (phthalazinone ether) [PPPE], poly (aryl amide), etc. have been widely studied because of their good thermal and mechanical properties, low fuel crossover and low costs [6e8]. Recent progress by many * Corresponding author. E-mail address: bhartigaur@gmail.com (B. Gaur). Available online at www.sciencedirect.com ScienceDirect journal homepage: www.elsevier.com/locate/he international journal of hydrogen energy xxx (2017) 1 e14 http://dx.doi.org/10.1016/j.ijhydene.2017.03.018 0360-3199/© 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved. Please cite this article in press as: Awasthi S, et al., Influence of hydrophobic block length and ionic liquid on the performance of multiblock poly (arylene ether) proton exchange membrane, International Journal of Hydrogen Energy (2017), http://dx.doi.org/10.1016/ j.ijhydene.2017.03.018