Electrical Conductivity of Anisotropic iPP Carbon Nanotube Thin Films

2012 ◽  
Vol 1410 ◽  
Author(s):  
Parvathalu Kalakonda ◽  
Erin A. Gombos ◽  
Gajinder S. Hoonjan ◽  
Georgi Y. Georgiev ◽  
Germano S. Iannacchione ◽  
...  
Keyword(s):  
Thin Film ◽  
Electrical Conductivity ◽  
Liquid Crystalline ◽  
Electronics Packaging ◽  
Induced Anisotropy ◽  
Crystal Forms ◽  
Liquid Crystalline Phases ◽  
Analogous Data ◽  
Large Spike ◽  
Film Nanocomposites

ABSTRACTPolymer and carbon nanotubes (CNTs) nanocomposites exhibit many properties that are not present in either the pure polymer or CNTs. The polymer crystallization kinetics and crystal forms are greatly changed by dispersion of CNTs nanotubes. In addition to various thermophysical properties, CNTs are metallic or semiconductive and highly anisotropic while the polymer hosts are typically excellent insulators and isotropic. In this work, measurements of the electrical conductivity, σ, of thin-film nanocomposites of isotactic polypropylene (iPP) and CNTs as a function of CNT concentration (0, 1, 2, and 5% by weight of CNT) and melt-shearing induced anisotropy in σ between parallel and perpendicular to the shearing axis is presented and compared them with analogous data for their thermal transport properties. The iPP host is itself one of the most widely used polymers, has liquid crystalline phases, and it is expected that iPP/CNT nanocomposites will be widely used in many polymer applications, some of which are for flexible electrodes, medical and electronics packaging and chemical sensors. The effect of melt-shearing is expected to induce anisotropy in the various properties of the iPP/CNT thin film that should be particularly apparent in the electrical conductivity of the polymer films, higher in the direction of the alignment and lower in the direction perpendicular to it. With increasing CNT content, the average conductivity 〈σ〉 increases slightly from 0 to 2% CNT then dramatically increases by eight orders of magnitude for 5%. The shear induced property of anisotropy, δσs = (σ‖ − σ┴) / 〈σ〉, overall increases with CNT content, revealing a large spike for the 1% sample, indicating the possibility of enhanced δσs due to optimized orienting procedures.

STRUCTURE AND PROPERTIES OF TITANIUM–POLYMER THIN FILM NANOCOMPOSITES

2005 ◽  
Vol 04 (01) ◽  
pp. 149-161 ◽  
Author(s):  
S. A. ZAVYALOV ◽  
E. I. GRIGORIEV ◽  
A. S. ZAVYALOV ◽  
I. A. MISURKIN ◽  
S. V. TITOV ◽  
...  
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Electrical Conductivity ◽  
Electrical Resistivity ◽  
Metal Content ◽  
Optical Absorption Spectroscopy ◽  
Heterogeneous Model ◽  
High Metal Content ◽  
Logarithmic Functions ◽  
Film Nanocomposites

Thin film titanium/poly-para-xylylene nanocomposites with controlled Ti content are prepared by vacuum coevaporation and cocondensation of Ti and paracyclophane. The structure and chemical composition of as-deposited samples and the changes of electrical resistivity, which they undergo upon heating, are studied by atomic force microscopy, optical absorption spectroscopy, and the temperature coefficient of the electrical resistivity. It is shown that vacuum coevaporation results in the production of nanocomposite thin films with average Ti particle size of 10–50 nm. The inorganic phase is shown to be amorphous Ti for the samples with high metal content, whereas for the low-filled nanocomposites it consists of amorphous titanium oxide. Two types of kinetics of the nanocomposite oxidation process have been found and modeled by (i) inverse logarithmic and (ii) logarithmic functions depending on the metal content within the thin film. After a long preconditioning period in air the electrical conductivity of the thin film nanocomposites was carefully investigated by two-probe DC measurements. A strong correlation between the concentration of Ti in the thin films and the electrical conductivity dependency on temperature is found and modeled by a heterogeneous model of conductivity.

Use of light microscopy in the qualitative and quantitative study of liquid crystalline order

1992 ◽  
Vol 50 (1) ◽  
pp. 264-265
Author(s):  
Christopher Viney
Keyword(s):  
Light Microscopy ◽  
Liquid Crystalline ◽  
Structural Characteristics ◽  
Molecular Order ◽  
Liquid Crystalline Phases ◽  
Convenient Technique ◽  
Liquid Crystalline Materials ◽  
Transparent Windows

Light microscopy is a convenient technique for characterizing molecular order in fluid liquid crystalline materials. Microstructures can usually be observed under the actual conditions that promote the formation of liquid crystalline phases, whether or not a solvent is required, and at temperatures that can range from the boiling point of nitrogen to 600°C. It is relatively easy to produce specimens that are sufficiently thin and flat, simply by confining a droplet between glass cover slides. Specimens do not need to be conducting, and they do not have to be maintained in a vacuum. Drybox or other controlled environmental conditions can be maintained in a sealed chamber equipped with transparent windows; some heating/ freezing stages can be used for this purpose. It is relatively easy to construct a modified stage so that the generation and relaxation of global molecular order can be observed while specimens are being sheared, simulating flow conditions that exist during processing. Also, light only rarely affects the chemical composition or molecular weight distribution of the sample. Because little or no processing is required after collecting the sample, one can be confident that biologically derived materials will reveal many of their in vivo structural characteristics, even though microscopy is performed in vitro.

Electron microscopy and diffraction of crystalline dendrimers and macrocycles

1993 ◽  
Vol 51 ◽  
pp. 1218-1219
Author(s):  
C. J. Buchko ◽  
P. M. Wilson ◽  
Z. Xu ◽  
J. Zhang ◽  
S. Lee ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Liquid Crystalline ◽  
Structural Information ◽  
High Resolution Electron Microscopy ◽  
Scanning Calorimetry ◽  
Tertiary Butyl ◽  
Phenyl Acetylene ◽  
Selected Area Electron Diffraction ◽  
Liquid Crystalline Phases ◽  
Resolution Electron

The synthesis of well-defined organic molecules with unique geometries opens new opportunities for understanding and controlling the organization of condensed matter. Here, we study dendrimers and macrocycles which are synthesized from rigid phenyl-acetylene spacer units, Both units are solubilized by the presence of tertiary butyl groups located at the periphery of the molecule. These hydrocarbon materials form crystalline and liquid crystalline phases which have been studied by differential scanning calorimetry, hot stage optical microscopy, and wide-angle x-ray scattering (WAXS).The precisely defined architecture of these molecules makes it possible to investigate systematic variations in chemical architecture on the nature of microstructural organization. Here we report on the transmission electron microscopy (TEM), selected area electron diffraction (SAED), and high resolution electron microscopy (HREM) studies of crystalline thin films formed by deposition of these materials onto carbon substrates from dilute solution. Electron microscopy is very attractive for gaining structural information on new molecules due to the scarcity of material to grow single crystals suitable for conventional crystallography.

Electrical Conductivity Manipulation and Switching Phenomena of Poly(p-Phenylenebenzobisthiazole) Thin Film by Doping Process

2010 ◽  
Author(s):  
Jiahua Zhu ◽  
Thomas C. Ho ◽  
Zhanhu Guo ◽  
Suying Wei ◽  
Sung Park ◽  
...  
Keyword(s):  
Thin Film ◽  
Electrical Conductivity

Charge mobility in discotic liquid crystalline porphyrins and phthalocyanines measured by PR-TRMC

2003 ◽  
Vol 07 (05) ◽  
pp. 342-350 ◽  
Author(s):  
John M. Warman ◽  
Jessica E. Kroeze ◽  
Pieter G. Schouten ◽  
Anick M. van de Craats
Keyword(s):  
Conjugated Polymers ◽  
Carrier Mobility ◽  
Liquid Crystalline ◽  
Alkyl Chain ◽  
Charge Carrier Mobility ◽  
Chain Structure ◽  
Coupling Element ◽  
Time Resolved ◽  
Liquid Crystalline Phases ◽  
Conductive Properties

The pulse-radiolysis time-resolved microwave conductivity technique, “PR-TRMC”, has been used to determine the charge carrier mobility within columnar stacks of mesomorphic discotic porphyrins and phthalocyanines. The influences of temperature, morphology and variations in the primary molecular structure are demonstrated and discussed. Both the mesomorphic and conductive properties are shown to be dramatically influenced by subtle changes in the peripheral alkyl chain structure or the core-to-chain coupling element. Mobilities close to 1 cm2.V−1.s−1 are found in crystalline solids, and well in excess of 0.1 cm2.V−1.s−1 in columnar, liquid crystalline phases. These values which are even larger than those determined by PR-TRMC for conjugated polymers and similar to values found for electrons and holes in organic single crystals.

Characterization of some mesogenic alkyl 1-thioglycosides

2002 ◽  
Vol 80 (8) ◽  
pp. 1162-1165 ◽  
Author(s):  
B Henrissat ◽  
G K Hamer ◽  
M G Taylor ◽  
R H Marchessault
Keyword(s):  
Phase Transition ◽  
Liquid Crystal ◽  
Solid State ◽  
Solid State Nmr ◽  
Liquid Crystalline ◽  
Liquid Crystal Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Liquid Crystalline Phases

A series of dodecyl 1-thio-β-D-glycosides has been synthesized and characterized (DSC, NMR, CP MAS, X-ray diffraction) as possible new marking materials with liquid-crystalline properties. These compounds undergo solid to liquid crystal phase transitions at various temperatures, which depend on the nature of the carbohydrate part of the structure. Their liquid-crystalline phases show extreme shear thinning behaviour.Key words: liquid crystal, powder X-ray diffraction, phase transition, thioglycoside, solid-state NMR, marking material

Molecularly Mediated Thin Film Assembly of Nanoparticles on Flexible Devices: Electrical Conductivity versus Device Strains in Different Gas/Vapor Environment

ACS Nano ◽  
2011 ◽  
Vol 5 (8) ◽  
pp. 6516-6526 ◽  
Author(s):  
Jun Yin ◽  
Peipei Hu ◽  
Jin Luo ◽  
Lingyan Wang ◽  
Melissa F. Cohen ◽  
...  
Keyword(s):  
Thin Film ◽  
Electrical Conductivity ◽  
Flexible Devices ◽  
Film Assembly
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