Conformational and Orientational Characteristics of Chain Molecules Placed in Nematic Fields. Part IIReport as inadecuate




Conformational and Orientational Characteristics of Chain Molecules Placed in Nematic Fields. Part II - Download this document for free, or read online. Document in PDF available to download.



Abstract : Deuterium NMR quadrupolar splittings and 2H – 2H dipolar couplings observed from perdeuterated 1,6-dimethoxyhexane CD3OCD26OCD3 dissolved in a liquid crystal 4-methoxybenzylidene-4-n-butylaniline MBBA were analyzed using the single-ordering-matrix SOM and the Photinos-Samulski-Toriumi P-S-T models. Within the framework of the rotational isomeric state approximation, intramolecular interactions up to the third-order between atoms and groups separated by five bonds were considered. The geometrical parameters and intramolecular interaction energies determined from ab initio molecular orbital calculations were employed. The two simulation models yielded fair agreement between theory and experiment, but were found to give quite different images of the solute chain: the SOM model, the solute becomes rigid and extended to conform itself to the nematic field; the P-S-T model, the solute has almost the same degree of flexibility as in the free state, but populations of the anisotropic conformers are selectively enhanced. To reveal the true conformational characteristics of chain molecules in nematic fields, experimental techniques to enable direct and quantitative measurements of the bond conformations are necessary.





Author: Yuji Sasanuma

Source: https://hal.archives-ouvertes.fr/



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