Infrared spectroscopy of ion-induced cross-linked sulfonated poly(ether ether ketone)

Abstract

The dehydration of SPEEK-[H] (protonated sulfonated poly(ether ether ketone)) converts 3-fold symmetric (C 3V) hydrated sulfonate sites to sulfonic acid sites with no local symmetry (C 1). Like Nafion-[H], SPEEK-[H] C 3V and C 1 environments afford IR group modes (C 3V,HF (1087 cm-1); C 3V,LF (1026 cm-1) and C 1,HF (1362 cm-1); C 1,LF (904 cm-1)) due to the mechanical coupling of vibrational internal coordinates of an ether link with those of the sulfonate or sulfonic acid exchange site. C 3V and C 1 bands are inversely correlated during membrane hydration/dehydration. Hydrated SPEEK-[M] (M: Cu 2+ , Ni 2+ , Cd 2+ , Pb 2+ , Sr 2+ or Ba 2+) exhibits SPEEK-[H] C 3V bands because cation waters of hydration preclude binding to the hydrated exchange site. When cation hydration spheres are thermally stripped at high vacuum, SPEEK-[M] C 3V bands supplant SPEEK-[H] C 3V bands, inducing SPEEK cross-linking. Incomplete cross-linking is evidenced by low intensities of SPEEK-[M] C 1,HF bands. The 1362 cm-1 band intensities are inversely correlated with cation hydration enthalpies.

Group Vibrational Mode Assignments as a Broadly Applicable Tool for Characterizing Ionomer Membrane Structure as a Function of Degree of Hydration

“…These assignments are further supported by augmenting eigenvector animations (SI Video 1–28) with experimental spectra obtained by altering the exchange site environment (e.g., state of hydration, ion speciation, derivatization of the ionomer, etc. ). ,− …”

“…Infrared (IR) and Raman spectroscopy, correlated to density functional theory (DFT) calculated normal-mode analyses, facilitate characterization of the PFSI exchange site environment versus state of hydration. ,− DFT, a quantum mechanical description of electronic, structural, and vibrational properties of molecular and crystalline systems, is based on the Hohenberg and Kohn theorems. − The total system energy is a functional of electron density. The exact ground state may be obtained if this functional is known.…”

Microstructure, mechanical properties and heat-resistance properties of bismaleimide composites modified synergistically by alumina and two kinds of thermoplastic resins

“…29 It is confirmed that the introduction of sulfonic acid group did not change the basic structure of PEEK, and PEEK has been successfully sulfonated. 30 Figure 2 shows the SEM image and energy spectrum (EDS) of PEEK and SPEEK. It can be seen from Figure 2(a) that PEEK structure is tight within a certain range and there are a little holes, Figure 2(c) demonstrates the microcosmic morphology of SPEEK, which is quite different from PEEK.…”

Preparation and properties of semi-IPN proton exchange membranes based on SPEEK and cross-linked PSt-DVB for direct methanol fuel cells

“…[6][7][8] Sulfonated poly(ether ether ketone) (SPEEK) is a PEM that can potentially be applied for DMFCs as SPEEK exhibits high proton conductivity, good mechanical properties, and low-cost production. [9][10][11] However, proton conductivity depends on the degree of sulfonation (DS). SPEEK membranes prepared at high DS have poor dimensional stability, high methanol diffusion, and low mechanical properties.…”