Conformation of aliphatic chains

The conformations, can be detected by the changes in the intensity of sensitive bands in IR spectra by using model compounds (low-molecular-weight and linear polymers) and compare the results with networks. The differences in the behaviour of conformationally sensitive bands reflect the differences in the behaviour of aliphatic chains in different compounds. To detect the bands sensitive to the internal rotation, we have measured the spectra (50-4000 cm 1) of model compounds A and B. 

The increase of ASj with m indicates that, for polymer molecules with longer aliphatic spacers, the conformations of these chains and the placement of the mesogenic units were increasingly more ordered for the mesophase (smectic) relative to the isotropic phase ... 

The repulsion forces dominating in aliphatic hydrocarbons lead to a trans conformation of the chain. The balance between attraction and repulsion forces can be changed for some of the possible conformations by the presence of neighboring atoms with lone electron pairs or by the presence of electronegative substituents. In these cases, the attractions... 

The motions of a flexible aliphatic chain attached to a rigid molecular core are analyzed theoretically by means of a master equation for random walk between the sites identified with the stable conformers of the chain, as an extension in the time domain of the Rotational Isomeric State approximation. 

Jones, F.R., Scales, L.E., and Semiyen, J.A. (1974) Equilibrium ring concentrations and statistical conformations of polymer-chains 13. Cyclics in 2 aliphatic polyesters. Polymer, 15,738-742. 

Packing Effects on the Conformation of Polymer Chains in the Crystals The case of Aliphatic Polyamides, 50... 

PACKING EFFECTS ON THE CONFORMATION OF POFYMER CHAINS IN THE CRYSTAFS THE CASE OF ALIPHATIC POLYAMIDES... 

The use of ordered supramolecular assemblies, such as micelles, monolayers, vesicles, inverted micelles, and lyotropic liquid crystalline systems, allows for the controlled nucleation of inorganic materials on molecular templates with well-defined structure and surface chemistry. Poly(propyleneimine) dendrimers modified with long aliphatic chains are a new class of amphiphiles which display a variety of aggregation states due to their conformational flexibility [38]. In the presence of octadecylamine, poly(propyleneimine) dendrimers modified with long alkyl chains self-assemble to form remarkably rigid and well-defined aggregates. When the aggregate dispersion was injected into a supersaturated... 

Despite the fact that many groups of scientists have been interested in finding systems with high barriers to rotation, purely open-chain hindered aliphatic systems such as di-f rf-butyl(2,2,3,3-tetramethylbutane) showed barriers to rotation of ca. 16 kcal/mol at the most (129). Recent studies (130) on similar systems agree with the earlier ones. Evidently some device is necessary to lock the conformation of the open-chain compound. 

Fig. 32a and b. The conformation of the ligand 5c in its thiourea complex and the disorder of the chain ends. Side view of the 5e-thiourea complex showing hydrogen bond contacts (parts of the aliphatic chain have been omitted for clarity)421... 

NMR studies showed that in polar solvents (DMSO, DMF) catenane 45 adopts a supramolecular conformation (II) that allows the amide protons to interact via multiple hydrogen bonds with solvent molecules and at the same time buries the lipophilic chains in the center of the molecule (Figure 18). In contrast, NMR spectra in nonpolar solvents indicate that the aliphatic chains are situated on the outer sphere of the catenane, whereas the isophthaloyl units are arranged in a way that ensures optimal intramolecular hydrogen-bonding (I). 

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