Third order nonlinear polymers

Porter, P.L., Guha, S., Kang, K. and Frazier, C.C., "Structural dependence of platinum and palladium poly-ynes on third-order nonlinearity," Polymer 32 1756 (1991). 

Optical properties of cyanines can be usefiil for both chiral substituents/environments and also third-order nonlinear optical properties in polymer films. Methine-chain substituted die arbo cyanines have been prepared from a chiral dialdehyde (S)-(+)-2-j -butylmalonaldehyde [127473-57-8] (79), where the chiral properties are introduced via the chiral j -butyl group on the central methine carbon of the pentamethine (die arbo cyanine) chromophore. For a nonchiral oxadicarbocyanine, the dimeric aggregate form of the dye shows circular dichroism when trapped in y-cyclodextrin (80). Attempts to prepare polymers with carbocyanine repeat units (linked by flexible chains) gave oligomers with only two or three repeat units (81). However, these materials... 

Up to now, many conjugated polymers have been found to possess large and very rapid third-order nonlinear optical response, which originates from the one-dimensionally delocalized ji-conjugation system along the polymer chain. Their application to the all optical signal processing devices has been expected. 

Aromatic poly(benzothiazole)s are thermally and thermooxidatively stable and have outstanding chemical resistance and third-order nonlinear optical susceptibility. Aromatic poly(benzothiazole)s can be spun into highly-oriented ultrahigh strength and ultrahigh modulus fibers. However, this type of polymer is insoluble in most organic solvents. Therefore, hexafluoroisopropylidene units are introduced in the polymer backbone to obtain soluble or processable aromatic poly(benzothiazole)s. 

Another chemical approach to improve our microscopic understanding of optical nonlinearities is a study of nonlinear optical behavior of sequentially built and systematically derivatized structures. Most past work for third-order nonlinearities have focused on conjugated polymers. This ad hoc approach is not helpful in identifying functionalities necessary to enhance optical nonlinearities. A systematic study and correlation of Y values of systematically varied structure is an important approach for material development. 

Model Polymers with Distyrylbenzene Segments for Third-Order Nonlinear Optical Properties... 

In summary, it appears that poly silanes and polygermanes have large third order nonlinear susceptibilities, particularly for materials containing only a saturated sigma bonded polymer backbone. This is consistent with their large polarizabilities and the extensive sigma delocalization along the backbone. In some instances, the... 

In the mid 1980s, conjugated polymers were a hot topic in nonlinear optics. Many people promoted third-order nonlinear optics based on conjugated polymers and predicted their incorporation in future all-optical applications. However, the disillusionment came during the beginning of nineties when it was realized that it will not be so easy to have all required parameters under control. The initial hopes did not fulfill on the short time scale and quite some problems were left to be tackled. 

The area of molecular nonlinear optics has been rejuvenated by efforts to investigate three-dimensional multipolar systems, functionalized polymers as optoelectronic materials, near infrared optical parametric oscillators and related aspects.71 There have been some advances in chromophore design for second-order nonlinear optical materials 72 these include onedimensional CT molecules, octopolar compounds and organometallics. Some of the polydiacetylenes and poly(/>-phenylenevinylene)s appear to possess the required properties for use as third-order nonlinear optical materials for photonic switching.73... 

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... 

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