Nonequilibrium Phase Diagram of Sticky Nanotube Suspensions

Hobbie, Erik K.; Fry, D.

doi:10.1103/physrevlett.97.036101

Cited by 118 publications

(96 citation statements)

References 24 publications

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“…These changes in conductivity are related with the non-equilibrium state of CNT in high viscous matrices under these quiescent conditions [18] driven by either the entropic forces of selforganization [19] or the high attractive interparticle potential [20][21][22] overcoming its limited Brownian motion. These processes together with the filler re- arrangements due to relaxation of polymer chains at high temperatures, can form conductive agglomerates from the initially dispersed CNT [16,[22][23][24].…”

Section: Annealing Effectmentioning

confidence: 99%

Modifying the electrical behaviour of polypropylene/carbon nanotube composites by adding a second nanoparticle and by annealing processes

Palza

Garzón²,

Arias³

2012

Express Polym. Lett.

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Abstract.The effect of different nanoparticles on the geometrical percolation transition of multi-wall carbon nanotubes (CNT) in polypropylene (PP) composites was studied. Our results show that the electrical conductivity of PP/CNT composites (around 2 vol%) can be tuned depending on the characteristic of the third component. Non-conductive layered silica fillers disrupt the CNT percolated network reducing the electrical conductivity of the composite. Spherical nanoparticles otherwise, either copper metal or silica-based, decrease the percolation threshold down to 0.5 vol% of CNT. These results cannot be explained by previous theories about the effect of a second particle on the electrical behaviour of polymer/CNT composites such as the interparticle bridging or the excluded volume. The effect of annealing in the melt was further analyzed and our results show that depending on the concentration and the type of filler, the electrical conductivity of the composites can be increased several orders of magnitude.

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Section: Annealing Effectmentioning

confidence: 99%

Modifying the electrical behaviour of polypropylene/carbon nanotube composites by adding a second nanoparticle and by annealing processes

Palza

Garzón²,

Arias³

2012

Express Polym. Lett.

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“…The formation of extended networks of particles dispersed in a fluid gives rise to a discontinuous change in the rheological [1][2][3][4][5] and electrical [6][7][8][9] properties of the dispersion at concentrations around the so-called percolation threshold. Historically, percolation theory was first used by Flory [10] to explain the phenomenon of gelation in thermosetting polymers.…”

Section: Introductionmentioning

confidence: 99%

Modelling percolation in fibre and sphere mixtures: Routes to more efficient network formation

Rahatekar

Shaffer

Elliott

2010

Composites Science and Technology

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“…Emerging questions are the effect that shear has when interfaces of varying softness are present or when applied to phases with positional order. Examples of attractive colloids where shear alignment is interesting for industrial applications are carbon nanotubes [10], wormlike micelles [11], or polymers.…”

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confidence: 99%

Helicopter rotation and smectic-isotropic coexistence of strongly attractive rods

Ripoll

2011

Phys. Rev. E

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Hydrodynamic simulations of strongly attractive rodlike colloids are performed with and without shear flow. In the absence of flow, the isotropic-nematic coexistence becomes isotropic-smectic A, and the interfacial properties clearly vary with increasing attraction strength. In the presence of shear flow, a new collective rotation appears in which the director rotates in the vorticity-flow plane in a similar fashion to the movement of the rotor of a helicopter. DOI: 10.1103/PhysRevE.83.040701 PACS number(s): 64.70.M−, 82.70.Dd, 64.60.−i, 83.50.−v Liquid crystals in equilibrium, and in the presence of flow fields, show a very rich structural and dynamical behavior. Equilibrium phase diagrams display coexistence between isotropic (I), where rods are randomly oriented, nematic (N), where rods have a orientational preference, smectic (Sm), with both orientational and positional order, and crystalline phases, where the positional order is long ranged [1]. Attraction induced by depletion interactions has been considered in analytical calculations and experiments [2,3] of rods with large aspect ratios (rod length L over rod diameter σ ). The broadening of existing coexistence regions like I-N and N-Sm has been determined, together with the appearance of new ones as I-I, N-N, and eventually also I-Sm. Computer simulations are a powerful tool that can provide a detailed description of these systems. Numerous simulations with repulsive rods of small aspect ratios, typically from 2 to 6, have studied phases with positional order (see, e.g., Ref.[4]). Simulations of thermotropic systems of Gay-Berne colloidal rods [5] with increasing attraction have reported the appearance of different phases as a function of the potential asymmetry. Gay-Berne forces become unrealistically thin at the ends with increasing aspect ratio. I-Sm coexistence has been obtained with such rods by keeping the two phases at different temperatures [6]. In the presence of shear flow, the phase diagram is fundamentally altered [7]. Isotropic phases tend to align with flow, and oriented phases may undergo orchestrated motions that have been characterized about two decades ago [8]. Nematic phases have shown rotations in the flow-gradient plane (similar to the blades of a mill) or with an angle tilted in the vorticity direction (similar to the paddle in a kayak). These rotations are known as tumbling and kayaking [9]. Emerging questions are the effect that shear has when interfaces of varying softness are present or when applied to phases with positional order. Examples of attractive colloids where shear alignment is interesting for industrial applications are carbon nanotubes [10], wormlike micelles [11], or polymers.In this Rapid Communication, we investigate by means of computer simulations the effect of large attractions on the I-N coexistence of systems of rods with aspect ratio 20. At rest, increasing the attraction transforms the nematic phase into the smectic and linearly decreases the interface width. In the presence of shear flow, a qualitativ...

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Nonequilibrium Phase Diagram of Sticky Nanotube Suspensions

Cited by 118 publications

References 24 publications

Modifying the electrical behaviour of polypropylene/carbon nanotube composites by adding a second nanoparticle and by annealing processes

Modifying the electrical behaviour of polypropylene/carbon nanotube composites by adding a second nanoparticle and by annealing processes

Modelling percolation in fibre and sphere mixtures: Routes to more efficient network formation

Helicopter rotation and smectic-isotropic coexistence of strongly attractive rods

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