Synthesis and characterization of modified κ-carrageenan for enhanced proton conductivity as polymer electrolyte membrane

PLoS One. 2017 Sep 28;12(9):e0185313. doi: 10.1371/journal.pone.0185313. eCollection 2017.

Abstract

Polymer electrolyte membranes based on the natural polymer κ-carrageenan were modified and characterized for application in electrochemical devices. In general, pure κ-carrageenan membranes show a low ionic conductivity. New membranes were developed by chemically modifying κ-carrageenan via phosphorylation to produce O-methylene phosphonic κ-carrageenan (OMPC), which showed enhanced membrane conductivity. The membranes were prepared by a solution casting method. The chemical structure of OMPC samples were characterized using Fourier transform infrared spectroscopy (FTIR), 1H nuclear magnetic resonance (1H NMR) spectroscopy and 31P nuclear magnetic resonance (31P NMR) spectroscopy. The conductivity properties of the membranes were investigated by electrochemical impedance spectroscopy (EIS). The characterization demonstrated that the membranes had been successfully produced. The ionic conductivity of κ-carrageenan and OMPC were 2.79 × 10-6 S cm-1 and 1.54 × 10-5 S cm-1, respectively. The hydrated membranes showed a two orders of magnitude higher ionic conductivity than the dried membranes.

MeSH terms

  • Calorimetry, Differential Scanning
  • Carrageenan / chemical synthesis*
  • Carrageenan / chemistry*
  • Dielectric Spectroscopy
  • Electric Conductivity
  • Electrolytes / chemistry*
  • Membranes, Artificial*
  • Microscopy, Electron, Scanning
  • Polymers / chemistry*
  • Proton Magnetic Resonance Spectroscopy
  • Protons*
  • Spectrometry, X-Ray Emission
  • Temperature
  • Thermogravimetry
  • X-Ray Diffraction

Substances

  • Electrolytes
  • Membranes, Artificial
  • Polymers
  • Protons
  • Carrageenan

Grants and funding

This research work is jointly financially supported by the Ministry of Education Malaysia through the Long-term Research Grant Scheme (LRGS/2013/UKM-UKM/TP/01) and the Universiti Kebangsaan Malaysia (UKM) through the University Research Grants (GUP-2016-038). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.