Third polydiacetylenes

Third-Order Nonlinear Susceptibility in Multilayers of Polydiacetylene... 

The experimental technique used to measure the third order nonlinear susceptibilities of polydiacetylenes was developed recently at our laboratory. (15) This technique utilizes the intensity-dependent dispersion relation of confined modes of PDA films and determines by measuring the change of coupling angles with... 

Polydiacetylenes are obtained as single crystals by topochemical solid-state polymerization of the monomer single crystal. These compounds have received considerable attention because of their one-dimensionally -conjugated structure. Their unique --electron structures, and therefore superior third-order nonlinear optical properties, have been extensively investigated. 

Huggins KE, Son S, Stupp SI. Two-dimensional suptamolecular assemblies of a polydiacetylene. 1. Synthesis, structure, and third-order nonlinear optical properties. Macromolecules 1997 30 5305-5312. 

The increasing use of optical fibre in the telecommunications network will, ultimately, require all-optical signal processing to exploit the full bandwidth available. This has led to a search for materials with fast, large third order optical nonlinearities. Most of the current materials either respond in the nanosecond regime or the nonlinearity is too small (1-3). Organic materials are attractive because of their ultra-fast, broadband responses and low absorption. However the main problem in the materials studied to date, e.g. polydiacetylenes (4) and aromatic main chain polymers (5), has been the small nonlinear coefficients. 

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... 

Another potential application of fully converted polydiacetylenes is based upon their unusual non-linear optical properties. Sauteret et al. found that the third order susceptibilities of TCDU and TS increases by about a factor of 600 upon polymerization and become comparable to those of inorganic semiconductors like GaAs or germanium. This is a consequence of the increase of n-electron delocalization upon polymerization. Polymeric diacetylenes can therefore be used as efficient elements for third harmonic generation. In Ref. this effect has been employed for tripling the frequencies of 1.89 pm and 2.62 pm radiation. 

Thus, subphthalocyanine 17 exhibits a large resonant third-order optical nonlinearity and fast response. The measured resonant third-order NLO response is two orders of magnitude larger than the off-resonant values of chloroboron subphthalocyanine, and of the same order of magnitude as the off-resonant values of polydiacetylene due to resonant enhancement. 

Sinclair and coworkersmeasured the third-order nonlinear optical susceptibility of rm 5 -polyacetylene. The measured susceptibility was 5 x 10 esu, which is comparable to the magnitude of the large nonlinear susceptibilities measured in the polydiacetylenes. 

It must be noted that the values reported in the literature vary over broad ranges. Therefore, the values listed here reflect only the general behavior of several classes of compounds. It can be seen in Table 3.5 that trans-polyacetylenes (PAs) and polydiacetylenes (PDAs) exhibit the largest third-order NLO susceptibilities. The x value of cis-PA (not shown) is more than an order of magnitude smaller than that of trans-PA. Derivatives of poly-p-phenylene, poly(phenyl-ene vinylene), and polythiophene also exhibit NLO activity, but to a much lesser extent than PAs and PDAs. As pointed out above, polysilanes also possess quite large x values. This is explained by the cr-conjugation of the silicon chain, which implies a pronounced delocalization of cr-electrons. A very large x value... 

Polydiacetylene Microcrystals for Third-Order Nonlinear Optics... 

Organic compounds with delocalized jr-electron systems, e,g., jr-conjugated polymers, are considered to be candidates for third-order nonlinear optical materials. Among them, polydiacetylenes (PDAs) are an important class of conjugated polymers that has attracted investigators from many different fields (7,2). PDAs, which can be obtained as single crystals by topochemical solid-state polymerization (5), have been extensively studied since 1976 (4). PDAs show large third-order nonlinear optical susceptibilities (5) and ultrafast optical... 

Third-Order Nonlinear Susceptibility of Polydiacetylene-Containing Polymeric Systems... 

During the late 1960s, Wegner reported that single-crystalline diacetylenes could be topochemically polymerized to ene-yne polydiacetylenes [78], and several groups subsequently applied this chemistry to crosslinking polymerizations in 2-D confinement. For example, Leblanc synthesized the dendrimer-based amphiphile 34 in which sixteen 10,12-pentacosadiynoic acid chains were coimected to the periphery of a third-generation poly(amidoamine) (PAMAM) dendrimer [79]. A monolayer of this dendritic amphiphile was prepared at the air/water interface, in which the... 

The optical absorption maxima are revealed to be at 520, 500 and 420 nm for PTV, MOPPV and PPV films, respectively. X-ray diffraction patterns indicate that the PAV films have low crystallinity. The values of these PAV films evaluated by third-harmonic generation (THG) measurement at 1.85 pm are found to be 5.85 x 10 " esu, 3.2 X 10 esu, and 7.8 x 10 esu for PTV, MOPPV and PPV films, respectively. These values are non resonant values and are almost the same as that reported for a processible polydiacetylene (n-butoxycarbonylmethyl urethane) (n-BCMU-PDA, n = 4,3) thin film [18]. 

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