Substrate-Dependent Molecular and Nanostructural Orientation of Nafion Thin Films

Douglas I. Kushner, Ahmet Kusoglu, Nikolas J. Podraza, Michael Anthony Hickner

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

The effects of film thickness and substrate composition on the ionomer structure in porous electrodes are critical in understanding pathways toward developing higher performance electrochemical devices, including fuel cells and batteries. Insights are gained into the molecular and nanostructural orientation dependence for thin Nafion films (12–300 nm thick) on gold, platinum, and SiO2 model substrates. Molecular orientation is determined from the birefringence measured using spectroscopic ellipsometry, while the nanostructural orientation of the ionic domains is measured using grazing-incidence small-angle X-ray scattering. Density functional theory calculations for the molecular polarizability of the Nafion backbone and side chain show complimentary contributions to the measured birefringence values for the material. Nafion films prepared on SiO2 substrates exhibit a nearly isotropic molecular and nanostructural orientation. Films on gold and platinum display parallel backbone orientations, relative to the substrate, with decreasing film thickness. However, a birefringence transition toward molecular isotropy is observed for 30 nm thick films on Au and Pt; while the ionic nanostructured domains continuously align parallel to the substrate. This apparent isotropic molecular orientation with increasing domain orientation highlights the difference between the backbone and side chain orientation, a key finding for elucidating transport in confined films at the interfaces.

Original languageEnglish (US)
Article number1902699
JournalAdvanced Functional Materials
Volume29
Issue number37
DOIs
StatePublished - Sep 1 2019

Fingerprint

Thin films
Birefringence
Substrates
thin films
Molecular orientation
Platinum
Gold
Film thickness
Fuel cells
birefringence
Ionomers
Spectroscopic ellipsometry
platinum
X ray scattering
film thickness
Thick films
Crystal orientation
Density functional theory
gold
perfluorosulfonic acid

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics

Cite this

Kushner, Douglas I. ; Kusoglu, Ahmet ; Podraza, Nikolas J. ; Hickner, Michael Anthony. / Substrate-Dependent Molecular and Nanostructural Orientation of Nafion Thin Films. In: Advanced Functional Materials. 2019 ; Vol. 29, No. 37.
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Substrate-Dependent Molecular and Nanostructural Orientation of Nafion Thin Films. / Kushner, Douglas I.; Kusoglu, Ahmet; Podraza, Nikolas J.; Hickner, Michael Anthony.

In: Advanced Functional Materials, Vol. 29, No. 37, 1902699, 01.09.2019.

Research output: Contribution to journalArticle

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