Electron Spin Resonance on polyurethanes – Vapor grown carbon nanofiber composites

• Discussed the degradation of the polymeric matrix during the synthesis/processing of nanocomposites.
• Reported the role of the nanofibers in the deactivation of free radicals induced in composites during the processing step.
• Concluded that charge transport is dominated by polarons.
• Correlated Electron Spin Resonance data with electrical conductivity data.
• Connected the percolation threshold for electrical conductivity with ESR data.

Electron Spin Resonance investigations on polyurethane – vapor grown carbon nanofiber composites are reported. The research focuses on the free radicals generated during the processing step and on the ESR spectrum of the conducting electrons delocalized over the carbon nanofiber. The deactivation of free radicals due to their interaction with the electrons residing on carbon nanofiber was analyzed and related to the enhanced stability of these composites. The dependence of the resonance line parameters on the concentration of the nanofiller is studied in detail. Experimental data indicates that the electrical conductivity is due to uncoupled electrons delocalized over the conducting domains of the nanofiller and suggests that the electrical conductivity is dominated by polarons. The percolation of the electrical conductivity is also reflected in the ESR data. The interactions between uncoupled electronic spins, as revealed by the line width dependence on the concentration of carbon nanofibers are discussed in detail.