Ion-containing block copolymers hold promise as next-generation proton exchange membranes in hydrogen and methanol fuel cells. These materials’ self-assembled ordered nanostructures facilitate proton transport over a wide range of conditions, a requirement for robust fuel cell performance. In this perspective, we will present an overview of the morphology and transport properties of ion-containing block copolymers that have been studied to gain insight into the fundamental behavior of these materials and, in some cases, are targeted toward applications in fuel cells and other electrochemical devices. We will discuss the challenges associated with predicting and obtaining well-ordered morphologies in block copolymers with high ion content, particularly those with chemistries that can withstand the chemical and mechanical stresses of the fuel cell, such as aromatic backbone block copolymers. New opportunities for ion-containing block copolymers in alkaline membrane fuel cells will also be reviewed.

Block Copolymers for Fuel Cells

Crystallization inhibition in solid dispersions of MK‐0591 and poly(vinylpyrrolidone) polymers

Ionomers are polymers with bonded ionic species that are used under conditions where the salt groups are in a condensed state. This Feature Article discusses the state of our understanding of ionomers and the historical applications of these nanostructured polymers. It also discusses modern methods for synthesizing new ionomers and describes a number of relatively new applications for ionomers and the potential use of these materials in contemporary technologies, including, shape memory and self-healing materials and supramolecular polymer systems.

Perspective: Ionomer Research and Applications

Electron paramagnetic resonance (EPR), Fourier transform infrared (FTIR), and solid-state 15N nuclear magnetic resonance (15N-NMR) spectroscopies were used to characterize the structure and relative strength of the interactions between metal sulfonate and amide groups in blends of lightly sulfonated polystyrene ionomers and an N-methylated polyamide, poly(N,N‘-dimethylethylene sebacamide), and low molecular weight model complexes. The metal sulfonate groups, which aggregate in the neat ionomer, were dispersed by the polyamide in the blend as a consequence of a complexation that involved the sulfonate cation and both the carbonyl oxygen and the amide nitrogen of the polyamide. The FTIR and 15N-NMR spectra were consistent with a 2pz electron redistribution model for the complex, in which electrons migrate from the nitrogen to the metal ion through the carbonyl group. The sulfonate anion did not appear to particpate in the complex, but it remained in the vicinity of the metal cation. The strength of the ion−...

Compatibilization of polymer blends by complexation. 1. Spectroscopic characterization of ion-amide interactions in ionomer/polyamide blends

Structure–property relationship in sulfonated pentablock copolymers

Differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) were used to characterize the phase behavior and interactions of blends of the free acid derivative and lithium and sodium salts of lightly sulfonated polystyrene (MSPS) with Bisphenol A polycarbonate (PC). The blends exhibited upper critical solution temperature (UCST) phase behavior and a miscibility window with respect to the sulfonation level. At a fixed blend composition, a minimum in the cloud point temperature occurs at the sulfonation level marking the middle of the miscibility window. The miscibility window depended on the sulfonate cation used. No interactions involving either the carbonate carbonyl group or the sulfonate groups were detected for any of the blends. Miscibility was attributed to intramolecular repulsive interactions within the ionomer.

Development of Miscible Blends of Bisphenol A Polycarbonate and Lightly Sulfonated Polystyrene Ionomers from Intrapolymer Repulsive Interactions

Blends of polyamide-6 with lithium ionomers of 9.8 and 5.4 mole percent sulfonated polystyrene, formed by combining solutions of these polymers, are miscible over a wide compositional range, but those with the equivalent sodium ionomers are not. The molecular origin of this difference is addressed by studying the far infared and infrared spectra of the blends and pure materials to follow changes in the interactions between the cations and their surroundings, and changes in the interactions between functional groups. Based on analysis of these spectra, a molecular level interpretation of the blending is proposed. The initial step involves both the interaction of one amide carbonyl with an Li + ion and simultaneous hydrogen bonding between an amide N-H and a sulfonate group. This eventually leads to formation of an Li(>CO) n + (n∼4) entity while the sulfonates are converted to the acid form through hydrogen bonding to the amide N-H groups. The Na + ion does not interact strongly enough with the amide groups to leave its sulfonate environment to a significant extent

Molecular interpretation of miscibility in polyamide‐6 blends with alkali ionomers of sulfonated polystyrene

Sulfonation of poly(oxy-1,4-phenyleneoxy-1,4-phenylenecarbonyl-1,4-phenylene), PEEK, improves its miscibility with poly(ϵ-caprolactam), Nylon-6 (N6). This article describes the thermal transitions and the specific interactions that occur for blends of the free acid derivative (H-SPEEK) and the lithium (Li-SPEEK) and zinc salts (Zn-SPEEK) of sulfonated PEEK (19.2 mol % sulfonation) with N6. The interactions responsible for miscibility were characterized by Fourier transform infrared (FTIR) spectroscopy. For blends of H-SPEEK and N6, miscibility is due to hydrogen bonding between the sulfonic acid and the amide group. For blends of N6 with the salts of SPEEK the specific interaction involves an ion-dipole complex of Li+ with the amide carbonyl or Zn2+ with the amide nitrogen. The relative strengths of the intermolecular interactions for the three types of blends increased as the cation was varied in the order: H+ < Li+ < Zn2+, and the Tgs of the mixtures increased in the same order. © 1996 John Wiley & Sons, Inc.

Xinya Lu

Papers

Development of Miscible Blends of Bisphenol A Polycarbonate and Lightly Sulfonated Polystyrene Ionomers from Intrapolymer Repulsive Interactions

Molecular interpretation of miscibility in polyamide‐6 blends with alkali ionomers of sulfonated polystyrene

Specific interactions and miscibility of blends of poly(ε‐caprolactam) and sulfonated PEEK ionomer