Dielectric and Conductive Properties of Poly(Methyl Methacrylate)/Single Wall Carbon Nanotube composites
Kenji Kano, Jan Obrzut
Polymers Division, National Institute of Standards and Technology, Gaithersburg, MD 20899-8541
Wei Zhou, Fangming Du, Karen I. Winey, John E. Fischer
Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6272
Materials Science & Engineering, Michigan Technological University
Houghton, MI 49931-1295
Single wall carbon nanotube and poly(methyl methacrylate) (PMMA) composite was investigated by means of broadband dielectric spectroscopy. We used two kinds of single wall carbon nanotube fillers, one is p-doped single wall carbon nanotube (p-SWNT); the other is functionalized by introducing octadecylamine (f-SWNT). 0.1 wt%, 1 wt% and 2 wt% nanotube concentration composite are prepared for p-SWNTs and f-SWNTs. The results of NIR spectroscopy indicate that p-SWNT is conductive and f-SWNT is non-conductive.
Large dielectric dispersion was observed in dielectric spectra of p-SWNT/PMMA composites over 1 wt% nanotube fraction. This dispersion was not observed in pure PMMA. Adding that, carbon nanotube fillers increase the conductivity of composites. Semiconductor order conductivity was observed for the samples that exhibit large dielectric dispersion. Because activation energy of this large dispersion is equal to activation energy of conductivity, we concluded that this dispersion is due to charge migrations of single wall carbon nanotube filler in PMMA matrix. Charges in p-SWNTs affect both conductivity and permittivity. In 0.1 wt% samples, only relaxations that are due to molecular motion of PMMA were observed.
There are no additional relaxation processes caused by existing SWNTs in f-SWNT/PMMA composites. The a relaxation process of PMMA was slowed by f-SWNTs indicating that mobility of polymer segments decreased by interaction between f-SWNTs and the PMMA backbones. We concluded that PMMA chains that are attached to surfaces of f-SWNTs were immobilized. Based on these results, fundamentals of enhanced properties by small amount of single wall carbon nanotube fillers will be discussed.
Name: Kenji Kano
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