Investigation of dielectric breakdown in silica-epoxy nanocomposites using designed interfaces

Michael Bell, Timothy Krentz, J. Keith Nelson, Linda Schadler, Ke Wu, Curt Breneman, Su Zhao, Henrik Hillborg, Brian Benicewicz

Research output: Contribution to journalArticlepeer-review

36 Scopus citations


Adding nano-sized fillers to epoxy has proven to be an effective method for improving dielectric breakdown strength (DBS). Evidence suggests that dispersion state, as well as chemistry at the filler-matrix interface can play a crucial role in property enhancement. Herein we investigate the contribution of both filler dispersion and surface chemistry on the AC dielectric breakdown strength of silica-epoxy nanocomposites. Ligand engineering was used to synthesize bimodal ligands onto 15 nm silica nanoparticles consisting of long epoxy compatible, poly(glycidyl methacrylate) (PGMA) chains, and short, π-conjugated, electroactive surface ligands. Surface initiated RAFT polymerization was used to synthesize multiple graft densities of PGMA chains, ultimately controlling the dispersion of the filler. Thiophene, anthracene, and terthiophene were employed as π-conjugated surface ligands that act as electron traps to mitigate avalanche breakdown. Investigation of the synthesized multifunctional nanoparticles was effective in defining the maximum particle spacing or free space length (Lf) that still leads to property enhancement, as well as giving insight into the effects of varying the electronic nature of the molecules at the interface on breakdown strength. Optimization of the investigated variables was shown to increase the AC dielectric breakdown strength of epoxy composites as much as 34% with only 2 wt% silica loading.

Original languageEnglish (US)
Pages (from-to)130-139
Number of pages10
JournalJournal of Colloid and Interface Science
StatePublished - Jun 1 2017
Externally publishedYes


  • Dielectric breakdown strength
  • Epoxy
  • Ligand engineering
  • Nanodielectric
  • RAFT polymerization
  • Surface modification

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Biomaterials
  • Surfaces, Coatings and Films
  • Colloid and Surface Chemistry


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