Polythiophenes, properties optical

Mechanical Properties of Polythiophenes Chemical properties Switching properties Optical properties of polythiophenes... 

Nilsson KPR, Rydberg J, Baltzer L, Inganas O (2003) Self-assembly of synthetic peptides control conformation and optical properties of a zwitterionic polythiophene derivative. Proc Natl Acad Sci 100 10170-10174... 

Polythiophenes (PTs) have received a great deal of attention due to their electrical properties, environmental stability in doped and undoped states, non-linear optical properties, and highly reversible redox switching [1]. Thiophene possesses a rich synthetic flexibility, allowing for the use of several polymerization methods and the incorporation of various side chain functionalities. Thus, it is of no great surprise that PTs have become the most widely studied of all conjugated polyheterocycles [184]. 

The polymerization of thiophene, to yield intractable polythiophene 48, was first carried out in a controlled manner in the early 1980s [185-188]. Even in such an unyielding form, this polymer displayed many promising optical and electronic properties. Unfortunately, its lack of processibility precluded further exploration of these attractive attributes. Since then, the synthesis of soluble pol-... 

Radical cations and dications of oligothiophenes have been investigated by many research groups to understand the nature of polarons and bipolarons in polythiophenes which are responsible for the electrical and optical properties of these re-conjugated polymers. 

The second method is the synthesis of copolymers or derivatives of a parent conjugated polymer with more desirable properties. This method is the more traditional one for making improvements to a polymer. It modifies the structure of the polymer to increase its processibility without compromising its conductivity or its optical properties. All attempts to do this on polyacetylene have failed as they always significantly reduced its conductivity. However, such attempts on polythiophenes and polypyrroles proved more fruitful. 

We mentioned above that in real materials, disorder of any kind localizes the excitations over a limited length on the chain, generating effective conjugation lengths so that, for instance, the optical properties are those of a finite, often quite small, molecule. It may well be that excitons are very important in such cases. This has been proposed, for instance, for substituted PPV and polythiophene [83]. This is not by itself a proof that were it possible to prepare the corresponding perfect chain, the excitons would still be important there, although this is precisely what is found in PDAs, because electron correlations have different intensities on different CPs. 

Conjugated polymers satisfy these requirements and have thus emerged as the most widely studied materials for their susceptability. Some of the examples of conjugated polymers, that have been studied for their third order NLO properties, are polydiacetylenes, poly-p-phenylenevinylenes and polythiophenes. However, CVD has only been used in the case of poly-p-phenylenevinylenes (PPV) [section 3.4], although values have not been reported. An excellent review of third order nonlinear optical properties of PPV in general, can be found in literature. Recently, McElvain et al. ° reported the values of CVD polyazomethines to be... 

Intercalation of electroactive polymers such as polyaniline and polypyrrole in mica-type layered silicates leads to metal-insulator nanocomposites. The conductivity of these nanocomposites in the form of films is highly anisotropic, with the in-plane conductivity 10 to 10 times higher than the conductivity in the direction perpendicular to the film. Conductive polymer/oxide bronze nanocomposites have been prepared by intercalating polythiophene in V2O5 layered phase, which is analogous to clays. °° Studies of these composites are expected not only to provide a fundamental understanding of the conduction mechanism in the polymers, but also to lead to diverse electrical and optical properties. 

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