Processing, morphology, and water uptake of nafion/Ex situ stöber silica nanocomposite membranes as a function of particle size

Beatrice Muriithi, Douglas A Loy

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

Because of the bicontinuous phase structure of Nafion with small hydrophilic channels, formation of composites with silica colloids to improve thermal stability, hydration, and proton conductivity should be influenced by size and surface functionality of the colloids. To test this hypothesis, we prepared batches of silica particles between 20 and 400 nm in diameter with narrow polydispersities using a modified Stöber procedure. Some particles were subsequently surface-modified using mercaptopropyltriethoxysilane. Enough particles were mixed with Nafion in alcohols to achieve 5 wt % silica in the final membranes, which were made by casting and drying. Membrane top and bottom surface and cross-section morphologies were examined with AFM and SEM to determine how the particles were dispersed. We discovered that casting the membranes from dispersions with viscosities less than 65 cPs led to larger particles floating to the top surface of the membrane where they were easily dislodged from the dry membrane. Membranes cast from more viscous solutions exhibited homogeneous distributions of particles. Water uptake was over 60% higher in nanocomposites with unmodified silica particles than for Nafion and about 15% higher than for Nafion with in situ generated silica particles, but showed no trend in water uptake correlating with particle size. Surface silated particles of all sizes appeared to have reduced water uptake relative to Nafion alone.

Original languageEnglish (US)
Pages (from-to)6766-6773
Number of pages8
JournalACS Applied Materials and Interfaces
Volume4
Issue number12
DOIs
StatePublished - Dec 26 2012

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Silicon Dioxide
Nanocomposites
Particle size
Silica
Membranes
Water
Processing
Colloids
Casting
Proton conductivity
Polydispersity
Phase structure
Dispersions
Hydration
perfluorosulfonic acid
Drying
Alcohols
Thermodynamic stability
Viscosity
Scanning electron microscopy

Keywords

  • morphology
  • Nafion membrane
  • silica nanoparticles
  • water uptake

ASJC Scopus subject areas

  • Materials Science(all)

Cite this

Processing, morphology, and water uptake of nafion/Ex situ stöber silica nanocomposite membranes as a function of particle size. / Muriithi, Beatrice; Loy, Douglas A.

In: ACS Applied Materials and Interfaces, Vol. 4, No. 12, 26.12.2012, p. 6766-6773.

Research output: Contribution to journalArticle

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