Multiblock Copolymers with Highly Sulfonated Blocks Containing Di‐ and Tetrasulfonated Arylene Sulfone Segments for Proton Exchange Membrane Fuel Cell Applications

Abstract

(arylene ether sulfone)s with different block lengths and ionic contents are tailored for durable and proton-conducting electrolyte membranes. Two series of fully aromatic copolymers are prepared by coupling reactions between non-sulfonated hydrophobic precursor blocks and highly sulfonated hydrophilic precursor blocks containing either fully disulfonated diarylsulfone or fully tetrasulfonated tetraaryldisulfone segments. The sulfonic acid groups are exclusively introduced in ortho positions to the sulfone bridges to impede desulfonation reactions and give the blocks ion exchange capacities (IECs) of 4.1 and 4.6 meq. g −1 , respectively. Solvent cast block copolymer membranes show well-connected hydrophilic nanophase domains for proton transport and high decomposition temperatures above 310 °C under air. Despite higher IEC values, membranes containing tetrasulfonated tetraaryldisulfone segments display a markedly lower water uptake than the corresponding ones with disulfonated diarylsulfone segments when immersed in water at 100 °C, presumably because of the much higher chain stiffness and glass transition temperature of the former segments. The former membranes have proton conductivities in level of a perfluorosulfonic acid membrane (NRE212) under fully humidified conditions. A membrane with an IEC of 1.83 meq. g −1 reaches above 6 mS cm −1 under 30% relative humidity at 80 °C, to be compared with 10 mS cm −1 for NRE212 under the same conditions.solubilization of conductive polymers such as poly(thiophene)s. [4] Still, perhaps the most important application area of these robust polymers is currently as proton exchange membranes for polymer electrolyte fuel cells, which are highly energy efficient and potentially environmentally benign power devices. [5,6] Today, perfluorosulfonic acid polymers such as Nafion are considered as state-of-the-art membranes because of their high chemical stability and high proton conductivity under a wide humidity range at moderate operating temperatures. [7,8] Nevertheless, the Nafion membrane suffers from general disadvantages such as high cost, high fuel permeability and a low mechanical modulus. More seriously, the Nafion membrane has a tendency to dehydrate above 80 °C, leading to lower conductivities. It thus fails to meet the current industrial demands which call for operating temperatures above 100 °C. [9,10] Over the last decade, an extensive research effort has been directed toward developing alternative membranes based on sulfonated hydrocarbon polymers to overcome the drawbacks of Nafion. [11,12] The use of hydrocarbon-based monomers and building blocks has widely expanded the possibilities to vary and control the structure and function of the membranes in relation to fluorocarbon-based approaches. For example, a wide range of sulfonated high-performance aromatic polymers has been prepared and their films have subsequently been evaluated and demonstrated as prospective fuel cell membranes. Among these polymers, sulfonated poly(arylene ether sulfone)s (SPAESs) have been ex...

Ion Transport by Nanochannels in Ion-Containing Aromatic Copolymers

“…48 In these systems, DFBP was used as a chain extender (Scheme 1-(2)) rather than a monomer. Multiblock SPAES 2 were synthesized by polycondensation of hydrophilic oligomer, hydrophobic bisphenolterminated oligomer, and the chain extender DFBP.…”

Segmented Tetrasulfonated Copoly(Arylene Ether Sulfone)s: Improving Proton Transport Properties by Extending the Ionic Sequence

“…[33][34][35] In this work, SPAES copolymers with tetrasulfonated units were prepared by using the sBCPSBPos monomer in direct polycondensations. [33][34][35] In this work, SPAES copolymers with tetrasulfonated units were prepared by using the sBCPSBPos monomer in direct polycondensations.…”

Multiblock poly(Phenylene ether nitrile)s with pendant sulfoalkoxyl side chain for H2/air fuel cells at low humidity condition

“…Jannasch et al also synthesized a series of multiblock poly(arylene ether sulfone)s, in which the sulfonic acid groups were exclusively introduced in ortho ‐positions on the sulfone bridges to impede desulfonation reactions. These membranes showed good proton conductivity of over 6 mS cm −1 under 30% RH at 80 °C . Quite recently, a fully aromatic sulfonated ABA triblock copolymer [sulfonated poly(phenylene oxide)‐b‐poly(arylene ether sulfone)‐b‐sulfonated poly(phenylene oxide)] was reported by Lee's group.…”