Polyacetylenes highly ordered

When PVAPAC films, optimized with respect to conjugation length distribution and PAC concentration, are stretched in a controlled manner they turn into highly dichroic transparent neutral grey POLPAC filters (Fig. 1.10). The absence of coloration is indicative of an exceptionally highly ordered PAC state in these novel all polymer broadband polarizers based on polyacetylene (POLPAC ). 

In every case a highly ordered, highly conducting polyacetylene is produced (corresponding to [2]). Details of the conductivities, orientation, anisotropy, etc. are reported elsewhere. 

Yu ZQ, Lam JWY, Zhu CZ, Chen EQ, Tang BZ. Side-chain liquid crystalline polyacetylenes with increasing length of alkyl tails from highly ordered smectic to smectic C phase. Macromolecules 2013 46 588-96. 

Durham polyacetylene occurs in a highly disordered state on conversion from the precursor polymer [90], but using stretch orientation techniques during the conversion reaction, a high degree of order with long conjugated sequences can be achieved [91-93],... 

Durham route, the metathesis polymerization of 7,8-bis(trifluoromethyl)tricyclo[4.2.2.0]deca-3,7,9-triene gives a high-molecular weight soluble precursor polymer that is thermally converted to polyacetylene (equation 19.6). The precursor polymer is soluble in common organic liquids and easily purified by reprecipitation. The end product can be aligned giving a more compact material with bulk densities on the order of 1.05 —1.1 g/cm. ... 

The structure/property relationships that govern third-order NLO polarization are not well understood. Like second-order effects, third-order effects seem to scale with the linear polarizability. As a result, most research to date has been on highly polarizable molecules and materials such as polyacetylene, polythiophene and various semiconductors. To optimize third- order NLO response, a quartic, anharmonic term must be introduced into the electronic potential of the material. However, an understanding of the relationship between chemical structure and quartic anharmonicity must also be developed. Tutorials by P. Prasad and D. Eaton discuss some of the issues relating to third-order NLO materials. 

Extensive ir-conjugation is also often associated with enhanced conductivity in organic systems (6). Polyacetylene and polythiophene which in the doped state exhibit very high electrical conductivity also exhibit relative large third-order nonlinear optical effects in... 

Partially substituted derivatives of polyacetylene are synthesized via the ring-opening metathesis polymerization (ROMP) of cyclooctatetraene (COT) and its derivatives. Certain poly-COT derivatives afford soluble, highly conjugated poly acetylenes. These materials exhibit large third-order optical nonlinearities and low scattering losses. 

Although the literature of gas separation with microporous membranes is dominated by inorganic materials, polymer membranes have also been tried with some success. The polymers used are substituted polyacetylenes, which can have an extraordinarily high free volume, on the order of 25 vol %. The free volume is so high that the free volume elements in these polymers are probably interconnected. Membranes made from these polymers appear to function as finely microporous materials with pores in the 5 to 15 A diameter range [71,72], The two most... 

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