Rational design of aromatic surfactants for graphene/natural rubber latex nanocomposites with enhanced electrical conductivity

Azmi Mohamed*, Tretya Ardyani, Suriani Abu Bakar, Masanobu Sagisaka, Yasushi Umetsu, J. J. Hamon, Bazura Abdul Rahim, Siti Rahmah Esa, H. P.S. Abdul Khalil, Mohamad Hafiz Mamat, Stephen King, Julian Eastoe

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

21 Citations (Scopus)
302 Downloads (Pure)

Abstract

Hypothesis: Graphene nanoplatelets (GNPs) can be dispersed in natural rubber matrices using surfactants. The stability and properties of these composites can be optimized by the choice of surfactants employed as stabilizers. Surfactants can be designed and synthesized to have enhanced compatibility with GNPs as compared to commercially available common surfactants. Including aromatic groups in the hydrophobic chain termini improves graphene compatibility of surfactants, which is expected to increase with the number of aromatic moieties per surfactant molecule. Hence, it is of interest to study the relationship between molecular structure, dispersion stability and electrical conductivity enhancement for single-, double-, and triple-chain anionic graphene-compatible surfactants. Experiments: Graphene-philic surfactants, bearing two and three chains phenylated at their chain termini, were synthesized and characterized by proton nuclear magnetic resonance (1H NMR) spectroscopy. These were used to formulate and stabilize dispersion of GNPs in natural rubber latex matrices, and the properties of systems comprising the new phenyl-surfactants were compared with commercially available surfactants, sodium dodecylsulfate (SDS) and sodium dodecylbenzenesulfonate (SDBS). Raman spectroscopy, field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), and high-resolution transmission electron microscopy (HRTEM) were used to study structural properties of the materials. Electrical conductivity measurements and Zeta potential measurements were used to assess the relationships between surfactant architecture and nanocomposite properties. Small-angle neutron scattering (SANS) was used to study self-assembly structure of surfactants. Findings: Of these different surfactants, the tri-chain aromatic surfactant TC3Ph3 (sodium 1,5-dioxo-1,5-bis(3-phenylpropoxy)-3-((3phenylpropoxy)carbonyl) pentane-2-sulfonate) was shown to be highly graphene-compatible (nanocomposite electrical conductivity = 2.22 × 10−5 S cm−1), demonstrating enhanced electrical conductivity over nine orders of magnitude higher than neat natural rubber-latex matrix (1.51 × 10−14 S cm−1). Varying the number of aromatic moieties in the surfactants appears to cause significant differences to the final properties of the nanocomposites.

Original languageEnglish
Pages (from-to)34-47
Number of pages14
JournalJournal of Colloid and Interface Science
Volume516
Early online date11 Jan 2018
DOIs
Publication statusPublished - 15 Apr 2018

Keywords

  • Graphene nanoplatelets (GNPs)
  • Natural rubber latex (NRL)
  • Anionic surfactant
  • Surfactant stabilization
  • Surfactant self-assembly

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