Polydiacetylene electrical properties

Owing to the mechanism of the topochemical reaction the polyconjugated polymer chain is of exceptional purity and stereochemical regularity. Polydiacetylene crystals are thus ideally suited to study the inherent optical and electrical properties of polyconjugated chains. These unique features have attracted considerable attention and in recent years the topochemical polymerization of diacetylenes has developed to... 

As a consequence of both the unusual backbone structures and the comparatively high perfection of (SN) and polydiacetylene crystals, electrical properties are observed which differ dramatically from conventional polymers. However, the conductive properties of (SN) and the photoconductive properties of the polydiacetylenes are still limited by phase imperfections. 

Polydiacetylenes are particularly interesting for their optical and electrical properties. For example, large third-order nonlinear optical effects can be produced. Extensive electronic conjugation is required for such behaviour and polydiacetylenes produce the largest values yet observed for example, the solid state polymer of (20) exhibits a value of esu, and the LB polymer of (10) with n = 16,m = S exhibits a non-resonant value of 4 x 10 esu. Insulating properties are... 

Lochner, K., Reimer, B., and Bassler, H., Anisotropy of electrical properties of a polydiacetylene single crystal, Chem. Phys. Lett., 41, 388, 1976. 

Most of the reported conjugated polymers with nonlinear optical or electrical activities are carbon-carbon conjugated systems, such as the extensively studied polyenes (e.g., polyacetylenes [15], polydiacetylenes [16,17], poly-/ -phenylenes) and heteroaromatic polymers (e.g., polypyrroles, polythiophenes, polycarbazoles, polyanilines) [18]. The synthetic methods, applications, and the structure-property relationships of these polymers have also been substantially investigated [19-21]. 

The nonlinear optical properties of polydiacetylenes are subject of an increasing interest in last years (1-4). This is due to the fact that polydiacetylenes are a one-dimensionnal system of higly polarizable conjugated tt elections The polarization depends strongly on electron delocalization length Moreover, the electronic origin of hyperpolarizability implies short response times On the other hand, the wave dispersed measurements of molecular hyperpolarizabilities yield information about forbidden electronic transitions In fact the bulk polarization can be developped in external electric field power series ... 

Hankin, S.H.W. Sandman, D.J., "Recent Studies of Raman Spectroscopy of Polydiacetylene Crystals Poly- Ipudo", p. 661 in Chiang, L.Y. Garito, A.F. Sandman, D.J. (Eds.), Mat. Res. Soc. Symp. Proc., Vol. 247 Electrical, Optical, and Magnetic Properties of Organic Solid State Materials, Materials Research Society, Pittsburgh, Pennsylvania, USA (1992). 

The preparation of polydiacetylene single crystals will be outlined. Studies of oligomeric intermediates observed during polymerization will be described since they are of theoretical interest and provide information on the properties of short polymer chains which cannot be obtained in any other way. The electronic properties of these crystals, as revealed by studies of their spectra and electrical conductivity, will be discussed together with models used to interpret them. Finally studies of disordered systems will be described, in particular the recent observations of carrier recombination in damaged and disordered samples. The outstanding experimental and theoretical problems will be emphasised. 

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