Polydiacetylene , nonlinear optics applications

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]. 

A number of studiesof the nonlinear optical properties of polydiacetylene multilayers have been undertaken. It is obvious from these investigations that there is a strong possibility.that these materials have applications in integrated optics as wave guide materials. However this will be dependent on the ability to control morphology and structure in these layers, thus indicating the... 

Third order NLO materials have potential applications such as optical switches, modulations and other nonlinear optical devices [189], Polydiacetylenes [190], polyacetylenes [191], poly(phenylene-vinylene)s [192] and polythiophenes [193] have large third-order nonlinear susceptibility % ranging from lO to 10 esu. 

For third order nonlinear application, however, it is the concentration of the NLO dye that is of paramount importance, not the orientational aspects. The third order response is typically dependent on the extent and nature of electronic conjugation. Polydiacetylene, for example, shows very high because of the delocalized electronic structure along the n-conjugated polymer chains. The large dye molecules posses quite reasonable molecular hyperpolarizability. A high concentration of these dyes without a concomittant deterioration of linear optical properties can lead to useful bulk third order NLO coefficients. 

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