Proton Conducting Phase‐Separated Multiblock Copolymers with Sulfonated Poly(phenylene sulfone) Blocks for Electrochemical Applications: Preparation, Morphology, Hydration Behavior, and Transport

Abstract

A family of multiblock copolymers consisting of alternating fully sulfonated hydrophilic poly(phenylene sulfone) and hydrophobic poly(phenylene ether sulfone) segments are prepared and characterized. The multiblock copolymers are formed by the coupling of preformed hydrophilic and hydrophobic blocks using a specially designed coupling agent. The block lengths (degree of polymerization) of both segment types were varied in order to control the ion exchange capacity. Solution cast films show spontaneous nanophase separation leading to distinct bicontinuous morphologies with correlation lengths around 15 nm. The hydrophobic phase gives the membranes their advantageous viscoelastic properties even at high temperatures under both wet and dry conditions, while proton conductivity takes place within the hydrophilic phase. Since the properties of fully sulfonated poly (phenylene sulfone)s are locally preserved within the hydrophilic domain, the membranes show very high proton conductivity and high hydrolytic stability. The very high degree of water dispersion within the hydrophilic domains leads to very low electro‐osmotic water drag. Because of their superior transport and stability properties these multiblock copolymers have a great potential for use as a substitute for perfluorosulfonic acid membranes which are used as separator materials in electrochemical applications such as polymer electrolyte membrane (PEM) fuel cells and redox flow batteries.

Polymerized Paired Ions as Polymeric Ionic Liquid–Proton Conductivity

“…PolyILAMPS is very highly polarizable, and increasing polarization with increasing water (and other solvent) content makes it a potential gate material for ChemFETs in polar solvent sensing. The stimuli responsiveness of the imidazolium group has been used to transform the zwitterionic resin into an acid sulfonate form using HPF 6 . This acid sulfonate form is 2-3 orders of magnitude more highly proton conducting than Nafi ons in the limit of zero water content, suggesting a matrix more suited to proton transport than the hydrophobic Nafi on structure.…”

“…We therefore doped polyILAMPS at a molar ratio of 1 HPF 6 per monomer (charge pair) in order to transform this material into a fully protonated sulfonic acid resin. The PF 6 − anion binds strongly with the imidazolium group (in the presence of water), and in so doing reduces cationic repulsive barriers to proton diffusion. The protons provided by HPF 6 can associate with sulfonate groups and undergo facile diffusion.…”

“…Proton conducting membranes (PCM) are important topics of research and development because of their use and potential use as PEM (polyelectrolyte membranes) in fuel cells [1][2][3][4][5][6][7][8] and redox fl ow batteries. [ 6 ] Sulfonic acid sites are widely acknowledged [8][9][10][11] as preferred components in PCM, and the well-known monomer, AMPS (2-acrylamido-2-methyl-1-propanesulfonate), is a convenient way to formulate membranes to include the sulfonate moiety. [12][13][14][15][16] Reactive ionic liquid monomers and surfmers have been introduced [17][18][19][20][21][22][23][24][25] for the fabrication of diverse microporous and nanoporous membranes.…”

Ion Transport by Nanochannels in Ion-Containing Aromatic Copolymers

“…Contrary to the procedure of Jannasch, the highly sulfonated poly(arylene thioether sulfone) block end-capped with pentafluorophenyl was first oxidized by H 2 O 2 , followed by coupling with phenolterminated PAES block to form multiblock copolymers 8 (Scheme 2). 54 The novel poly(phenylene sulfone)-based multiblock copolymers 7 and 8 had distinct bicontinuous morphologies with nanochannel sizes of ∼15 nm, as shown by AFM, TEM, or SAXS. Very high proton conductivities were observed, but no hydrolytic and oxidative stabilities and fuel cell durability data were reported.…”

“…Inducing nanochannel formation for proton transport in these new generations of proton exchange membranes based on block copoly(phenylene sulfone)s 52,54 or poly(phenylene)-s 63−68 is beginning to be explored. Employing block copolycondensation as described previously, multiblock sulfonated poly(phenylene sulfone)s were prepared by Jannasch and Meyer.…”