Physical Conjugated linear polymers

Wegner, G. Organic linear polymers with conjugated double bonds. In Chemistry and physics of one-dimensional metals. Keller, H. J. (ed.). New York Plenum Press 1977, pp. 297-314... 

In the polymerization of ethylene by (Tr-CjHsljTiClj/AlMejCl [111] and of butadiene by Co(acac)3/AlEt2Cl/H2 0 [87] there is evidence for bimolecular termination. The conclusions on ethylene polymerization have been questioned, however, and it has been proposed that intramolecular decomposition of the catalyst complex occurs via ionic intermediates [91], Smith and Zelmer [275] have examined several catalyst systems for ethylene polymerization and with the assumption that the rate at any time is proportional to the active site concentration ([C ]), second order catalyst decay was deduced, since 1 — [Cf] /[Cf] was linear with time. This evidence, of course, does not distinguish between chemical deactivation and physical occlusion of sites. In conjugated diene polymerization by Group VIII metal catalysts -the unsaturated polymer chain stabilizes the active centre and the copolymerization of a monoolefin which converts the growing chain from a tt to a a bonded structure is followed by a catalyst decomposition, with a reduction in rate and polymer molecular weight [88]. 

In this review, we discuss the electrode/electrochemical properties and technological applications of -conjugated polymers. It is organized by material and the matmals are grouped in two classes, the polyaromatic polymer films such as the polymer derivatives of aniline, pyrrole, and thiophene, and the linear polyenes such as polyacetylene, polythiazyl. The report does not intend to review the preparation procedures or the physical properties of these materials since they have been summarized elsewhere It is also limited to work published in the scientific literature without attempting to include the numerous patents which have appeared in the last few years. 

Summing up this Chapter we note that the non-linear excitations play a dominant role in various physical applications of conjugated polymers. But a hill understanding of the interplay of various mechanisms giving rise to these localized states has not been reached yet. 

Peierls distortion [1] in one dimension (ID) is an inherent trait of linear conjugated polymers, leading to a bond length alternation (BLA). The usual chemical nomenclature for it is conjugation. Examples include polyacetylene and polyyne, two materials which have been studied by the physics and chemistry community for a very long time (see, e.g. the book [2] and the papers cited therein). For... 

Conducting polymers have some similarities to conventional polymeric materials, but it is clearly the extensive main-chain tt conjugation and its implicit stiffness with respect to chain bending and twisting that most influences the overall physical behavior. As a direct consequence, virtually all linearly unsubstituted conducting polymers, as shown in Fig. 25.1 are found to be intractable and infusible. These model systems also tend to form crystalline phase structures with many common features. Hence these compounds may be con-... 

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