Interplay of Hopping and Percolation in Organic Conducting Blends

Fraysse, J.; Planès, J.

doi:10.1002/(sici)1521-3951(200003)218:1<273::aid-pssb273>3.0.co;2-s

Cited by 15 publications

(7 citation statements)

References 7 publications

(7 reference statements)

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“…Values of t in the region of 1.3 have, in fact, been observed in a number of bulk systems. These include tϭ1.33 and tϭ1.42 in separate polyaniline-PMMA networks 22,23 and tϭ1.3 in polyethelene-carbon black composites. 24 One possible explanation for this is that the charge must flow solely through the conductive network which itself may be a fractal object of fractal dimension in the region of 2.…”

Section: A DC and Frequency Independent Ac Conductivitysupporting

confidence: 72%

Experimental observation of scaling laws for alternating current and direct current conductivity in polymer-carbon nanotube composite thin films

Kilbride¹,

Coleman²,

Fraysse³

et al. 2002

Journal of Applied Physics

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739

527

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Alternating current ͑ac͒ and direct current ͑dc͒ conductivities have been measured in polymer-nanotube composite thin films. This was carried out for a range of concentrations of multiwall nanotubes in two polymer hosts, poly͑m-phenylenevinylene-co-2,5-dioctyloxyp-phenylenevinylene͒ ͑PmPV͒ and polyvinylalcohol ͑PVA͒. In all cases the dc conductivity DC was ohmic in the voltage range studied. In general the ac conductivity displayed two distinct regions, a frequency independent region of magnitude 0 at low frequency and a frequency dependent region at higher frequency. Both DC and 0 followed a percolation scaling law of the form ϰ(pϪp c ) t with p c ϭ0.055% by mass and tϭ1.36. This extrapolates to a conductivity of 1ϫ10 Ϫ3 S/m for 100% nanotube content. Such a low value reflects the presence of a thick polymer coating, resulting in poor electrical connection between tubes. This leads to the suggestion that charge transport is controlled by fluctuation induced tunneling. In the high frequency regime the conductivity increases with frequency according to an approximate power law with exponent sϷ0.92, indicative of hopping transport. The onset of this frequency independent conductivity scales with mass fraction for the PmPV composite due to the variation of correlation length with nanotube content. This behavior is discussed in terms of a biased random walk in three dimensions. In addition ac universality is demonstrated by the construction of a mastercurve.

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Section: A DC and Frequency Independent Ac Conductivitysupporting

confidence: 72%

Experimental observation of scaling laws for alternating current and direct current conductivity in polymer-carbon nanotube composite thin films

Kilbride¹,

Coleman²,

Fraysse³

et al. 2002

Journal of Applied Physics

Self Cite

739

527

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show abstract

“…Higher values of critical exponent of 4.1 and 4.5 have been reported for pulsed laser vaporization SWNT (PLV) and oxidized PLV poly[(m-phenylenevinylene)-co-[(2,5-dioctyloxy-pphenylene)vinylene]] (PmPV) nanocomposites. 26 The t values of 1.36 for PmPV and polyvinyl alcohol (PVA) carbon nanotube, 28 1.33 and 1.42 for separate PMMpolyaniline network, 29,30 and 2 and 2.9 for HiPco and oxidized HiPco-PmPV 26 have been reported. Values of t ϭ 3.1 and 3.2 for surface-modified carbon nanofiber polyimide nanocomposites have also been reported.…”

Section: Polymer Nanocomposite Characterizationmentioning

confidence: 99%

Highly Conductive Multifunctional Graphene Polycarbonate Nanocomposites

2010

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Graphene nanosheet-bisphenol A polycarbonate nanocomposites (0.027-2.2 vol %) prepared by both emulsion mixing and solution blending methods, followed by compression molding at 287 °C, exhibited dc electrical percolation threshold of ∼0.14 and ∼0.38 vol %, respectively. The conductivities of 2.2 vol % graphene nanocomposites were 0.512 and 0.226 S/cm for emulsion and solution mixing. The 1.1 and 2.2 vol % graphene nanocomposites exhibited frequency-independent behavior. Inherent conductivity, extremely high aspect ratio, and nanostructure directed assembly of the graphene using PC nanospheres are the main factors for excellent electrical properties of the nanocomposites. Dynamic tensile moduli of nanocomposites increased with increasing graphene in the nanocomposite. The glass transition temperatures were decreased with increasing graphene for the emulsion series. High-resolution electron microscopy (HR-TEM) and small-angle neutron scattering (SANS) showed isolated graphene with no connectivity path for insulating nanocomposites and connected nanoparticles for the conductive nanocomposites. A stacked disk model was used to obtain the average particle radius, average number of graphene layers per stack, and stack spacing by simulation of the experimental SANS data. Morphology studies indicated the presence of well-dispersed graphene and small graphene stacking with infusion of polycarbonate within the stacks.

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“…While a value of t = 1.48 seems to suggest the existence of a two dimensional charge transport system, various studies with obtained t values around 1.3 have claimed otherwise [52,54]. Bauhofer and colleagues [48] conducted a review of over 147 experimental studies on the electrical percolation of polymer composites with CNT, concluding that the value of t could not be related to any dimensional parameter and, therefore, no well-founded conclusion about CNT network geometry could be provided from most of the experimentally achieved values of t .…”

Section: Resultsmentioning

confidence: 99%

Effects of Carbon Nanotubes/Graphene Nanoplatelets Hybrid Systems on the Structure and Properties of Polyetherimide-Based Foams

2018

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Foams based on polyetherimide (PEI) with carbon nanotubes (CNT) and PEI with graphene nanoplatelets (GnP) combined with CNT were prepared by water vapor induced phase separation. Prior to foaming, variable amounts of only CNT (0.1–2.0 wt %) or a combination of GnP (0.0–2.0 wt %) and CNT (0.0–2.0 wt %) for a total amount of CNT-GnP of 2.0 wt %, were dispersed in a solvent using high power sonication, added to the PEI solution, and intensively mixed. While the addition of increasingly higher amounts of only CNT led to foams with more heterogeneous cellular structures, the incorporation of GnP resulted in foams with finer and more homogeneous cellular structures. GnP in combination with CNT effectively enhanced the thermal stability of foams by delaying thermal decomposition and mechanically-reinforced PEI. The addition of 1.0 wt % GnP in combination with 1.0 wt % CNT resulted in foams with extremely high electrical conductivity, which was related to the formation of an optimum conductive network by physical contact between GnP layers and CNT, enabling their use in electrostatic discharge (ESD) and electromagnetic interference (EMI) shielding applications. The experimental electrical conductivity values of foams containing only CNT fitted well to a percolative conduction model, with a percolation threshold of 0.06 vol % (0.1 wt %) CNT.

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Interplay of Hopping and Percolation in Organic Conducting Blends

Cited by 15 publications

References 7 publications

Experimental observation of scaling laws for alternating current and direct current conductivity in polymer-carbon nanotube composite thin films

Experimental observation of scaling laws for alternating current and direct current conductivity in polymer-carbon nanotube composite thin films

Highly Conductive Multifunctional Graphene Polycarbonate Nanocomposites

Effects of Carbon Nanotubes/Graphene Nanoplatelets Hybrid Systems on the Structure and Properties of Polyetherimide-Based Foams

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