Vinylidene optically active

In copolymers of NVC with various vinyl or vinylidenic optically active monomers it has been found that independent of the nature of the chiral comonomer, composition and distribution of monomeric units, the heteroaromatic moieties are always characterized by a more or less marked induced circular dichroism (F gs- 13 and... 

The preparation of optically active ruthenium vinylidene complexes with the objective of performing the asymmetric version of this reaction has been attempted but has led to moderate enantioselectivities [50, 51]. 

This is the most widely used method for preparing optically active polymers in fact the polymerization of many optically active compounds having a vinyl or vinylidene double bond has already been described. 

Obtaining polyrotaxanes by the statistical method through polymerization of various monomers in the presence of macrocycles was attempted by Maciejewski who investigated the thermal radical copolymerization of vinylidene chbride, methyl methacrylate (MMA), acrylonitrile (AN), acrylamide, and thdr mixtures with ace-tonaphtylene in aqueous and dimethylformamide solutions in the presence of p-cyclodextrin or of its acylic derivative. All these attempts failed, however. Only, when copolymerization was initiated by y-radiation with an exposure dose of 5 Mrad, did some of the above-listed monomers form polymers exhibiting optical activity. However, the rotation of the initial p-cyclodextrin was 162°, while that of the obtained products only l°-6°. Such a small polarization plane rotation angle could result only from an insignificant amount of macrocycles in the synthesized compounds. Therefore, for the purpose of a more successful synthesis of cyclodextrin-based rotaxanes, a number of researchers tried to introduce elements of directionality into... 

Circular dichroism is extensively employed in the stmctural study of biological polymers, but not in the study of synthetic polymers. This is because most biological polymers are optically active, whereas most synthetic polymers are not. However, if the optically active vinyl or vinylidene monomers are incorporated in a synthetic polymer, the synthetic polymr could become optically active. 

Two types of monomers A and B, have been distinguished on the basis of the relationship between their structure and polymer chirality. To the former type belong monomers, such as vinyl and vinylidene monomers, which need to be chiral in order to give optically active polymers, while monomers of the latter type such as suitably substituted dienes suffice to be prochiral. 

The synthetic approach to optically active polymers based on the copolymerization of prochiral carbazole containing monomers with easily available optically active vinyl or vinylidenic comonomers is by far the most convenient route to a large variety of optically active polymers. Accordingly, N-vinylcarbazole and spaced-carbazole containing vinyl monomers 11-14 have been copolymerized with different optically active monomers 15-20. 

It is known that vinyl aromatic monomers when inserted in copolymer macromolecules with optically active vinyl or vinylidenic monomers become optically active and may or may not contribute to the optical rotation of the whole polymer measured at the sodium D line In particular, by mvestigating the electronic transitions of the aromatic chromophores, it is general found that both symmetry forbidden and... 

In a more specialized approach, IL phases have been immobilized in membrane materials. Although the primary driver of this work was the use of these materials as electrochemical devices, they have also been investigated for catalytic applications [20]. Membrane materials composed of air-stable, room-temperature ILs and poly(vinylidene fluoride)-hexafluoropropene copolymers were prepared with the incorporation of the active catalyst species in the form of palladium on activated carbon. Optical imaging revealed that the prepared membranes contained a high dispersion of the palladium catalyst particles. Studies on the materials included evaluating their gas permeability and their catalytic activity for the hydrogenation reaction of propene. 

One active area of research is completely missing. These are the optical and electrical properties, with effects such as the high conductivity of doped conjugated polymers, electro-luminescence in polymeric light emitting diodes, or the ferro- and piezoelectricity of poly(vinylidene fluoride), to cite only a few examples. There is no good reason for this omission, only that I did not want to overload the book with another topic of different character which, besides, mostly employs concepts which are known from the physics of semi-conductors and low molar mass molecules. 

---