Molecular composites dopants

Conducting polymer composites have also been formed by co-electrodeposition of matrix polymer during electrochemical polymerization. Because both components of the composite are deposited simultaneously, a homogenous film is obtained. This technique has been utilized for both neutral thermoplastics such as poly(vinyl chloride) (159), as well as for a large variety of polyelectrolytes (64—68, 159—165). When the matrix polymer is a polyelectrolyte, it serves as the dopant species for the conducting polymer, so there is an intimate mixing of the polymer chains and the system can be appropriately termed a molecular composite. 

Aleshin, A. N., Mironkov, N. B., Suvorov, A. V., Conklin, J. A., Su, T. M., and Kaner, R. B., Electrical properties of ion implanted and chemically doped polyaniline films, in Materials Research Society Symposium Proceedings on Electrical, Optical and Magnetic Properties of Organic Solid State Materials III, Vol. 413, 1996, p. 609. Cameron, D. A., and Reynolds, J, R., Conducting molecular composites of polypyrrole with electroactive polymeric dopant ions, ACS Proc., 37, 684 (1996). 

The polyamides are soluble in high strength sulfuric acid or in mixtures of hexamethylphosphoramide, /V, /V- dim ethyl acetam i de and LiCl. In the latter, compHcated relationships exist between solvent composition and the temperature at which the Hquid crystal phase forms. The polyamide solutions show an abmpt decrease in viscosity which is characteristic of mesophase formation when a critical volume fraction of polymer ( ) is exceeded. The viscosity may decrease, however, in the Hquid crystal phase if the molecular ordering allows the rod-shaped entities to gHde past one another more easily despite the higher concentration. The Hquid crystal phase is optically anisotropic and the texture is nematic. The nematic texture can be transformed to a chiral nematic texture by adding chiral species as a dopant or incorporating a chiral unit in the main chain as a copolymer (30). 

Epitaxial Layers. Epitaxial deposition produces a single crystal layer on a substrate for device fabrication or a layer for multilevel conductive interconnects which may be of much higher quality than the substrate. The epitaxial layer may have a different dopant concentration as a result of introducing the dopant during the epitaxial growth process or may have a different composition than the substrate as in silicon on sapphire. Methods used for epitaxial growth include chemical vapor deposition (CVD), vapor phase epitaxy (VPE), liquid phase epitaxy (LPE), molecular beam epitaxy (MBE) and solid phase epitaxy (SPE). 

In order for efficient load delocalization and strength enhancement of a composite, there must be a strong interaction between the dopant fibers and polymer matrix. However, since CNTs are allotropes of carbon, they are inherently insoluble in any solvent. Hence, there are a number of strategies that have been used to modify the surface of CNTs to facilitate their interactions with the surrounding matrix. Not only are these methods essential for the dispersion and self-alignment of nanotubes throughout a polymer host (or on a surface for molecular devices), but may also assist in the... 

Oxygen migration in doped cerias has been recently studied with molecular dynamics methods by Inaba et al and Hayashi et These authors examined the systems (Ce02)i (A 203) /2 (where M = Y Gd La) with dopant contents in the range 0 — 15% mol. The diffusion coefficient of oxygen at 1273 K was evaluated from the simulations at different compositions with a maximum at around 10% mol of dopant. 

Electrochemically prepared PPY films with a variety of dopant anions, such as chloride, bromide, sulphate and tosylate have been smdied by ToF-SIMS [360], No structural information on the cationic PPY chains, such as molecular fragment of pyrrole [M H]" at m/z = 66 and 68, was observed in the positive ion spectra. Similar conclusion has been reported for the PPY-fiber composites [361], Nevertheless, the molecular specificity of SIMS allows the distinction between the different dopant anions in the negative ion mode. The... 

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