Oriented Electronically Conducting Polymers

PREPARATIVE METHODS AND PROPERTIES OF WELL ORIENTED ELECTRONICALLY CONDUCTING POLYMERS... 

One of the aims of the energy oriented electrochemistry laboratory (48) is to decompose water by means of light. The major difficulty is that the materials which are used at the present time are too expensive. Thus, the use of electronically conducting polymers is of great interest. 

Rotations around torsional barriers induce changes in chain conformation. For conjugated systems like polydiacetylenes, flow-induced changes in chain conformation can have a profound influence on the photon absorption and electronic conductivity properties of the material [73]. Flow-induced changes in molecular conformation form the basis for several technically important processes, the best known examples are the production of oriented fibers by gel spinning [74], the compatibility enhancement [75] and the shear-induced modification of polymer morphology [76]. 

This volume combines chapters oriented towards new materials with chapters on experimental progress in the study of electrochemical processes. G. E Evans reviews the electrochemical properties of conducting polymers, materials which are most interesting from a theoretical point of view and promise to open up new fields of application. His approach gives a survey of the main classes of such polymers, describing their synthesis, structure, electronic and electrochemical properties and, briefly, their use as electrodes. 

The electrical properties of the pyrolyzed polymer differ in a number of ways from those of polyacrylonitrile. The overall conductivity increases, while the activation energy of conductivity decreases. A rough correlation is found between a0 and E of equation 15 in that a high a0 was associated with a low E (57). Increasing the degree of orientation causes an increase in conductivity but the activation energy remains unaffected. This is typical of electronic conductivity. 

These polymeric heterocyclic nanotubes and nanowkes have redox properties similar to those of parent, bulk polymers and thek electronic conductivity is enhanced with respect to analogous bulk polymers (due to the preferential orientation of the polymer chains along the fibrils). 

Considerable interest has arisen recently about the possibility of carrying out chiral syntheses on conducting polymer substrates. In these systems, the reacting solute is required to adsorb onto the surface in a well-defined orientation prior to electron transfer from the substrate. The design and preparation of conducting polymers that have the correctly oriented receptor groups promises to be an area of active research in the future, since such systems may represent convenient and economic routes to biologically active compounds. 

Conducting polymers are considered to be quasi-one-dimensional materials. To be able to study the intrinsic properties of these materials, such as intra- and inter-chain electron motions, it is important to reach a high degree of orientation of the polymer chains. Orientation is also important for achieving a high conductivity in these materials, since an increased order also increases the overlap of orbitals between chains, and thus increases the hopping probability. 

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