Thermal Processing as a Means to Prepare Durable, Submicron Thickness Ionomer Films for Study by Transmission Infrared Spectroscopy

Abstract

A high temperature solution processing method was adapted to prepare durable, freestanding, submicrometer thickness films for transmission infrared spectroscopy studies of ionomer membrane. The materials retain structural integrity following cleaning and ion-exchange steps in boiling solutions, similar to a commercial fuel cell membrane. Unlike commercial membrane, which typically has thicknesses of >25 μm, the structural properties of the submicrometer thickness materials can be probed in mid-infrared spectral measurements with the use of transmission sampling. Relative to the infrared attenuated total reflection (ATR) technique, transmission measurements can sample ionomer membrane materials more uniformly and suffer less distortion from optical effects. Spectra are reported for thermally processed Nafion and related perfluoroalkyl ionomer materials containing phosphonate and phosphinate moieties substituted for the sulfonate end group on the side chain. Band assignments for complex or unexpected features are aided by density functional theory (DFT) calculations.

Investigation of chemical modification on tosyl-activated polystyrene microsphere magnetic particle surface by infrared microscopy

“…The peak at 1260 cm −1 may represent -SO 3 -vibration. 6,7 The peak at 1067 cm −1 is suspected to be -CH 3 rocking vibration or S-O stretching. 10 The peaks at 846 and 800 cm −1 also come from C-H bending vibration of benzene rings.…”

“…6,7 Wide and various applications on IR spectroscopy cover even the confirmation of bacterial attachment and changes on particles 3,8,9 and IR spectroscopy is still considered as one of the most widely used and reliable methods for chemical changes at the surface of materials. 3,6,7,[10][11][12][13][14][15]17,18 Here the infrared (IR) microscopic investigation results to prove the surface modification of polystyrene (PS)-coated magnetic microparticles, are reported. .…”

Does thermal treatment merely make a H2O-saturated Nafion membrane lose its absorbed water at high temperature?

“…These techniques include in situ Raman measurements, 25,26 atomic force microscopy, 27,28 small angle X-ray scattering (SAXS), 29 small angle neutron scattering, 30 neutron reflectivity, 5 etc. [31][32][33] Both of them emphasized the distinctive ability of the FTIR technique to distinguish different hydration levels of the Nafion membrane. Recently, by comparing the differences in the FTIR spectra of Nafion and its derivatives, Korzeniewski and Smotkin et al proposed a convincible analysis of the FTIR features of Nafion in the region from 850 to 1450 cm À1 .…”

Electronic Structure and Vibrational Mode Study of Nafion Membrane Interfacial Water Interactions

“…3 Developing durable membranes that have high proton conductivity and resistance to crossover of hydrogen and oxygen has been challenging. [4][5][6][7][8][9][10] Important research efforts aim to discern membrane transport mechanisms and manipulate membrane structure on the nanoscale. 11 The computational studies reported in the present paper support work in this area by taking steps toward elucidating molecular level interactions between water and fluorinated ionomer.…”

“…5,13,[26][27][28][31][32][33] Vibrational spectroscopy and the theoretical analysis of vibrational spectral properties provide an excellent tool to probe the interactions of water molecules confined in membranes. 13,16 Falk et al 14,15 discovered that the IR spectrum of hydrated Nafion membranes featured a very broad peak around 3500 cm -1 -3200 cm -1 , typical of bulk water spectra, but in addition to the broad peak were a few sharp peaks around 3600 cm -1 and 3700 cm -1 , not characteristic of bulk water.…”