title: New molecular scale insights into the α-transition of Nafion® thin films from variable temperature ATR-FTIR spectroscopy.
abstract: Ultrathin films of Nafion® have attracted significant attention in recent years owing to their application in a variety of electrochemical devices. For improved mechanical integrity, the films are often subjected to a thermal treatment step. In this paper, we report a variable-temperature Fourier transform infrared spectroscopy study of ultra-thin (14 to 660 nm) Nafion films on SiO2/Si substrates in the attenuated total reflection mode. A key finding is the dramatic increase in the intensity of the 636-624 cm-1doublet band, generally associated with CF2wagging or helix-reversal defect, observed at around 110 °C during in situ heating. This onset temperature provides a molecular link to the α-transition temperature of bulk Nafion and is the first time such an observation has been made using infrared spectroscopy. Smaller changes in the intensity and/or a shift of the other peaks in the region 1300-900 cm-1were noted.
authors.affiliation: Department of Chemical and Petroleum Engineering, University of Calgary, 2500 University Drive, Calgary, AB T2N 1N4, Canada. kkaran@ucalgary.ca.
authors.forename: V
authors.identifier: http://orcid.org/0000-0001-9814-339X
authors.initials: V
authors.lastname: Ozhukil Kollath
authors.affiliation: Department of Chemical and Petroleum Engineering, University of Calgary, 2500 University Drive, Calgary, AB T2N 1N4, Canada. kkaran@ucalgary.ca.
authors.forename: K
authors.initials: K
authors.lastname: Karan