Dispersion of single wall carbon nanotubes by in situ polymerization under sonication

Park, Cheol; Ounaies, Zoubeida; Watson, Kent A.; Crooks, R.; Smith, Joseph G.; Lowther, Sharon E.; Connell, John W.; Siochi, Emilie J.; Harrison, Joycelyn S.; Clair, Terry L. St.

doi:10.1016/s0009-2614(02)01326-x

Cited by 723 publications

(389 citation statements)

References 13 publications

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“…Conductivities ranging from insulating (10 À13 S/cm) to conductive (10 À6 S/cm) can be achieved in the alignment direction with a 0.03 wt % SWNT loading, which is lower than the percolation concentration for an isotropic dispersion. 5,24,25 Although slight alignment was observed at lower frequencies (0.01 and 0.1 Hz), it was not reflected in the conductivity of the composite, suggesting that the aligned clusters of the SWNT bundles percolate above 0.1 Hz under these conditions.…”

Section: Electrical Conductivity Of Swnt/uh Compositesmentioning

confidence: 97%

“…1 Successful structural reinforcement of polymer matrices by SWNTs has been reported where significant improvement of mechanical properties was achieved at very low SWNT loadings. [2][3][4][5][6][7] Recently, sensing and actuating capabilities of SWNTs and SWNT-polymer composites have been studied in response to temperature, chemical vapors, strain, stress, electrochemical, and electrical stimuli. [8][9][10][11][12][13] Shear forces have been frequently used for aligning inclusions along the flow direction to reinforce mechanical properties.…”

Section: Introductionmentioning

confidence: 99%

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Aligned single‐wall carbon nanotube polymer composites using an electric field

Park

Wilkinson

Banda

et al. 2006

J Polym Sci B Polym Phys

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223

120

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While high shear alignment has been shown to improve the mechanical properties of single-wall carbon nanotube (SWNT)-polymer composites, this method does not allow for control over the electrical and dielectric properties of the composite and often results in degradation of these properties. Here, we report a novel method to actively align SWNTs in a polymer matrix, which permits control over the degree of alignment of the SWNTs without the side effects of shear alignment. In this process, SWNTs were aligned via AC field-induced dipolar interactions among the nanotubes in a liquid matrix followed by immobilization by photopolymerization under continued application of the electric field. Alignment of SWNTs was controlled as a function of magnitude, frequency, and application time of the applied electric field. The degree of SWNT alignment was assessed using optical microscopy and polarized Raman spectroscopy, and the morphology of the aligned nanocomposites was investigated by high-resolution scanning electron microscopy. The structure of the field induced aligned SWNTs was intrinsically different from that of shear aligned SWNTs. In the present work, SWNTs are not only aligned along the field, but also migrate laterally to form thick, aligned SWNT percolative columns between the electrodes. The actively aligned SWNTs amplify the electrical and dielectric properties of the composite. All of these properties of the aligned nanocomposites exhibited anisotropic characteristics, which were controllable by tuning the applied field parameters.

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Section: Electrical Conductivity Of Swnt/uh Compositesmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Aligned single‐wall carbon nanotube polymer composites using an electric field

Park

Wilkinson

Banda

et al. 2006

J Polym Sci B Polym Phys

Self Cite

223

120

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“…In attempts to achieve well-dispersed CNTs in a polymer, functionalization of the CNT walls [9,10], use of surfactants [11], controlled duration of sonication of mixtures of CNTs in various solvents [12,13,14,15,16], in situ polymerization under sonication [17], in situ bulk polymerization [18], high speed mechanical stirring [19,20], and compounding using a twin screw extruder [21,22] have been used. The dispersion of the CNTs in the polymer was mainly determined by taking images using transmission electron microscopy (TEM), scanning electron microscopy (SEM), or optical microscopy.…”

Section: Introductionmentioning

confidence: 99%

Relationship between dispersion metric and properties of PMMA/SWNT nanocomposites

Kashiwagi

Fagan

Douglas

et al. 2007

Polymer

169

113

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Particle spatial dispersion is a crucial characteristic of polymer composite materials and this property is recognized as especially important in nanocomposite materials due to the general tendency of nanoparticles to aggregate under processing conditions. We introduce dispersion metrics along with a specified dispersion scale over which material homogeneity is measured and consider how the dispersion metrics correlate quantitatively with the variation of basic nanocomposite properties. We then address the general problem of quantifying nanoparticle spatial dispersion in model nanocomposites of single wall carbon nanotubes (SWNT) dispersed in poly(methyl methacrylate) (PMMA) at a fixed SWNT concentration of 0.5 % using a 'coagulation' fabrication method. Two methods are utilized to measure dispersion, UV-Vis spectroscopy and optical confocal microscopy. Quantitative spatial dispersion levels were obtained through image analysis to obtain a 'relative dispersion index' (RDI) representing the uniformity of the dispersion of SWNTs in the samples and through absorbance. We find that the storage modulus, electrical conductivity, and flammability containing the same amount of SWNTs, the relationships between the quantified dispersion levels and physical properties show about four orders of magnitude variation in storage modulus, almost eight orders of magnitude variation in electric conductivity, and about 70 % reduction in peak mass loss rate at the highest dispersion level used in this study. The observation of such a profound effect of SWNT dispersion indicates the need for objective dispersion metrics for correlating and understanding how the properties of nanocomposites are determined by the concentration, shape and size of the nanotubes. conditions. We introduce dispersion metrics along with a specified dispersion scale over which material homogeneity is measured and consider how the dispersion metrics correlate quantitatively with the variation of basic nanocomposite properties. We then address the general problem of quantifying nanoparticle spatial dispersion in model nanocomposites of single wall carbon nanotubes (SWNT) dispersed in poly(methyl methacrylate) (PMMA) at a fixed SWNT concentration of 0.5 % using a 'coagulation' fabrication method. Two methods are utilized to measure dispersion, UV-Vis spectroscopy and optical confocal microscopy. Quantitative spatial dispersion levels were obtained through image analysis to obtain a 'relative dispersion index ' (RDI) representing the uniformity of the dispersion of SWNTs in the samples and through absorbance. We find that the storage modulus, electrical conductivity, and flammability † This was carried out by the National Institute of Standards and Technology (NIST), an agency of the US Government and is not subject to copyright in the US. ‡ Correspondence to: T. Kashiwagi (E-mail: takashi.kashiwagi@nist.gov) 1 property of the nanocomposites correlates well with the RDI. For the nanocomposites containing the same amount of SWNTs, the relationships betw...

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“…The high degree of alignment for nanostructures with high aspect ratio can be understood within the framework of microhydrodynamics, in which the Péclet number, Pe, is estimated to be in the range of 10 3 to 10 6 ()1) for the lengths of nanostructures studied here 15,18 . Sequential etching and SEM imaging also show that the NTs are, like the NWs, located at the outer $60 nm of the BBFs, close to a two-dimensional layer, contrasting with NT composites made by solution casting or spin coating [19][20][21] , which usually contain randomly oriented NTs through the thickness of the films.…”

Section: Other Nanowire and Carbon Nanotube Bbfsmentioning

confidence: 99%

“…NW/NT suspensions (0.5 -1 g) were transferred to the polished top surface of the die, forming a membrane covering the gas outlet, and then N 2 gas (P ¼ 150-200 kPa) was introduced to initiate bubble expansion. The ring catches the top portion of the bubble and directs stable vertical expansion at an average speed of $10-15 cm min 21 . Bubble films were transferred to wafer substrates during the expansion process.…”

Section: Semi-automated Process For Producing Bubblesmentioning

confidence: 99%

Nanowires and Carbon Nanotubes

Liu

2006

Scanning Microscopy for Nanotechnology

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Many of the applications proposed for nanowires and carbon nanotubes require these components to be organized over large areas with controlled orientation and density. Although progress has been made with directed assembly and LangmuirBlodgett approaches, it is unclear whether these techniques can be scaled to large wafers and non-rigid substrates. Here, we describe a general and scalable approach for large-area, uniformly aligned and controlled-density nanowire and nanotube films, which involves expanding a bubble from a homogeneous suspension of these materials. The blown-bubble films were transferred to single-crystal wafers of at least 200 mm in diameter, flexible plastics sheets of dimensions of at least 225 3 300 mm 2 and highly curved surfaces, and were also suspended across open frames. In addition, electrical measurements show that large arrays of nanowire field-effect transistors can be efficiently fabricated on the wafer scale. Given the potential of blown film extrusion to produce continuous films with widths exceeding 1 m, we believe that our approach could allow the unique properties of nanowires and nanotubes to be exploited in applications requiring large areas and relatively modest device densities.Semiconductor nanowires (NWs) and carbon nanotubes (NTs) exhibit physical properties that make them attractive building blocks for many electronic and optical applications [1][2][3] . To realize such applications, researchers have directed considerable effort to the development of methods of assembly that might ultimately lead to integrated systems. For example, there have been studies of individual or small numbers of NW and NT devices prepared by random deposition, electric field directed assembly 4 , flowassisted alignment 5 , and selective chemical and biological patterning 6,7 , and up to centimetre-scale assembly of NWs using the Langmuir-Blodgett technique 8 . However, it is still unclear whether these methods can be extended to large-scale assembly of NWs and NTs on both rigid and flexible substrates with controlled alignment and density.Blown film extrusion is a well-developed process for the manufacture of plastic films in large quantities, which involves extruding a molten polymer and inflating it to obtain a balloon, which can be collapsed and slit to form continuous flat films with widths exceeding 1 m at rates in the order of 500 kg h 21 (refs. 9 -11). We have applied this basic idea for the first time to the formation of nanocomposite films where the density and orientation of the NWs and NTs are controlled within the film. The basic steps in our approach (Fig. 1a) consist of (i) preparation of a homogeneous, stable and controlled concentration polymer suspension of NWs or NTs, (ii) expansion of the polymer suspension using a circular die to form a bubble at controlled pressure, P, and expansion rate, where stable vertical expansion is achieved using an external vertical force, F, and (iii) transfer of the bubble film to substrates or open frame structures. BLOWN BUBBLE FILMSTo characte...

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Dispersion of single wall carbon nanotubes by in situ polymerization under sonication

Cited by 723 publications

References 13 publications

Aligned single‐wall carbon nanotube polymer composites using an electric field

Aligned single‐wall carbon nanotube polymer composites using an electric field

Relationship between dispersion metric and properties of PMMA/SWNT nanocomposites

Nanowires and Carbon Nanotubes

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