Regular chain

A deeper analysis [80] on this Cu - Dy chain showed that NN and NNN interactions are efficient above Tc and that inter spin-ladder ferromagnetic interaction is observed in this family of compounds [79-82]. Attempts were made to use the 3d tectons with other lanthanide precursors, such as hexanuclear lanthanide clusters. Regular chains were obtained with Dy-Cu ferromagnetic interaction but their close packing prevents observation of SCM behaviour [83]. 

First attempts to obtain 3d-4f-based regular chains were made with Cu-Tb chains that show characteristic features of SCM but without structural characterization [84, 85]. Similarly, Co - Dy based chains were obtained but showed very weak x" lx ratio making the analysis of the magnetic slow relaxation difficult [86]. Lastly, some magnetic interplay between manganese oxide chains and Dy09 units... 

The donors are in fact organized in + 1 charged dimers which stack to form regular chain... 

Indeed, in the world of tomorrow we can expect new aspects of polymer solids to extend the conventional and successful structure ideas of this century. These, of course, were the recognition as molecular identities of the chains of repeating chemical monomers. The circumstances of those entities have resulted in interesting concepts of solubilities, viscosity, and other mechanics, and especially thermodynamic limitations m mutual solubility or comparability of polymer mixtures. But we have known for decades that even homogeneous regular chain polymers such as Carothers polyesters and polyamides formed solids with manifold imperfections and irregularities, such as order-disorder crystal configurations.(22,23)... 

According to the scheme of Figure 12, in the framework of a regular chain-migratory mechanism the C2 and some Cs symmetric metallocenes lead to iso- and syndiotactic polymers, respectively. In fact, for the C2 symmetric systems the same propene enantioface is enchained at each... 

In the framework of the regular chain migratory mechanism of Figure 12, the enantioface selectivities we have calculated for the C2- and Cs-symmetric catalysts of Figures 13 and 14, explain the iso- and syndiospecificity experimentally found for the corresponding real catalysts [89-91]. 

Figure 11.3 The effect of imino acids on protein structure. The presence of the imino acids proline and hydroxyproline introduces a constraint into the angles of the peptide bond which results in a bend in the previously regular chain structure.

It turns out that the insertion of a next molecule of propene in the branched alkyl metal complex is much slower than the insertion of propene in a regular chain formed after a 1,2 insertion. In several catalysts studied this leads to a situation in which a great deal of the catalyst sites are "dormant", i.e. the metal is tied up in unreactive secondary alkyl metal complexes. If eventually an... 

Smallest constitutional unit, the repetition of which constitutes a regular macromolecule, a regular oligomer molecule, a regular block, or a regular chain. 

Many properties of polyamides are attributable to the formation of hydrogen bonds between the NH and CO groups of neighboring macromolecules. This is evidenced by their solubility in special solvents (sulfuric acid, formic acid, m-cresol), their high melting points (even when made from aliphatic components), and their resistance to hydrolysis. In addition, polyamides with a regular chain structure crystallize very readily. 

A polymer which is in principle crystallisable because of its regular chains, may crystallise too slowly to develop, under normal circumstances, a detectable degree of crystallinity. In such a case the kinetics play the major role. 

This difference in the properties arises from the overall stiffness of the polymeric chains. Flory explained these differences in the properties by conformational energy considerations (45). In H-T PIB, the energy difference in changing the chain conformation is not pronounced. This causes the chain to become flexible. In contrast, H-H PIB exhibits a large rotation barrier around its adjacent dimethyl substituted carbon atoms. Thus, H-H PIB can not change its conformations, which results in a stiff and regular chain that is crystalline (19). 

While, in recent years, many laboratories have demonstrated that nearly every synthetic polymer can crystallize in the form of single crystals (13) consisting of lamellae formed by regular chain folding (Figure 3), it is clear that extreme condi-tions-i.e., very slow crystallization or very dilute solutions, are required for these structures to form. Under normal conditions, such as those encountered in any industrial process, the polymer usually crystallizes in the form of less ordered, large structures, called spherulites. 

Fig. 5 Schematic drawing of single crystal with regular chain folding...

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