FTIR-ATR study of water uptake and diffusion through ion-selective membranes based on plasticized poly(vinyl chloride)

Tom Lindfors, Fredrik Sundfors, Lajos Höfler, Róbert E. Gyurcsányi

Research output: Contribution to journalArticle

44 Citations (Scopus)

Abstract

In this paper, the water uptake and diffusion of water through ion-selective membranes based on plasticized poly(vinyl chloride) (PVC) have been studied by FTIR-ATR spectroscopy. The diffusion of water was modeled by the finite-difference method and the obtained diffusion coefficients are reported for membranes plasticized with bis(2-ethylhexyl) sebacate (DOS) and 2-nitrophenyl octyl ether (oNPOE). The influence of various common membrane additives such as lipophilic salts and ionophores on the water uptake was also determined through representative membrane formulations (potassium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (KTFPB) and/or calcium iono-phore IV (ETH 5234)). The best fits of the time dependent water concentration changes in the membrane upon water uptake were obtained with a model consisting of two diffusion coefficients describing fast (ca. 1.5 107 cm2 s 1) and slow (ca. 9.5 109 cm2 s 1) diffusion of water in the PVC membranes. In contrast to the water uptake of the membranes, the diffusion rates were found to be practically independent of the membrane composition. It is shown that KTFPB and ETH 5234 decrease the water uptake whereas it is facilitated by a higher plasticizer content of the membrane. Monomeric, dimeric, clustered and bulk water could be distinguished by deconvolution of the FTIR-ATR spectra, which is important for understanding the water uptake mechanism.

Original languageEnglish
Pages (from-to)1914-1922
Number of pages9
JournalElectroanalysis
Volume21
Issue number17-18
DOIs
Publication statusPublished - Sep 1 2009

Keywords

  • Conducting materials
  • Diffusion
  • FTIR-ATR
  • Finite-difference modeling
  • Ion-selective membranes
  • Membranes
  • Plasticized poly(vinyl chloride)
  • Water uptake

ASJC Scopus subject areas

  • Analytical Chemistry
  • Electrochemistry

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