Book
Molecular Simulation of Cholesteric Liquid-Crystal Polyesteramides: Conformational and Structure Analysis by Rietveld Refinement
| العنوان: | Molecular Simulation of Cholesteric Liquid-Crystal Polyesteramides: Conformational and Structure Analysis by Rietveld Refinement |
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| المؤلفون: | Pérez Méndez, Mercedes, José Fayos Alcañiz, Marc Meunier |
| المساهمون: | CSIC - Unidad de Recursos de Información Científica para la Investigación (URICI), orcid |
| بيانات النشر: | InTechOpen |
| سنة النشر: | 2022 |
| المجموعة: | Digital.CSIC (Consejo Superior de Investigaciones Científicas / Spanish National Research Council) |
| مصطلحات موضوعية: | Cholesteric LC polyesteramides, Molecular Modeling, WAXS synchrotron radiation source, Conformational analysis, Rietveld refinement, Crystal polymerin chains models |
| الوصف: | Molecular modeling techniques are applied to polyesteramides designed as PNOBDME (C34H38N2O6)n and PNOBEE (C26H22N2O6)n, synthesized and characterized as cholesteric liquid crystals -through the condensation reaction between 4 and 40-(terephthaloyl- diaminedibenzoic chloride (NOBC) and racemic glycol: DL- 1,2 dodecanediol, or DL-1,2-butanediol, respectively, being chemical modifications of precursor multifunctional cholesteric LC polyesters, adding new properties but holding their helical macromolecular structures. Although the starting raw materials were racemic, these cholesteric LC polymers exhibit unexpected optical activity and chiral morphology. For that reason, conformational analysis is studied on the monomer models of PNOBDME and PNOBEE. Four helical conformers models, experimentally observed by NMR, are proposed for each cholesteric polyesteramide: Rgg, Rgt, Sgg, Sgt. Polymerization of the monomeric conformers, with minima energies, has been simulated and used to reproduce the crystalline fraction observed by x-ray diffraction. Three orders of chirality are observed in the structure of the polymer chains: One due to the asymmetric carbon atoms, a second chirality due to the two successive rotations of the benzene groups, along the main chain, within the monomer which implies the formation of helical molecules, for both R and S chirality and still, a third chirality corresponding to the twisting of the rigid/semirigid cholesteric LC polymer chains. All these factors contribute to the net optical activity observed in these materials. Crystal packing is simulated in triclinic primitive P1cells, with molecular chains oriented parallel to the z-axis (c lattice parameter equal to the pitch length of each simulated polymer helix) and parameters a, b, α, β and γ, obtained by Pawley refinement from the known structures of precursor polyesters. The simulated x-ray diffraction patterns of the proposed crystal models fit, after successive Pawley and Rietveld refinement cycles, the experimental WAXS. Powder ... |
| نوع الوثيقة: | book part |
| اللغة: | English |
| ردمك: | 978-1-83881-944-6 1-83881-944-4 |
| Relation: | Sí; https://www.intechopen.com/books/10957; http://hdl.handle.net/10261/280929 |
| DOI: | 10.5772/intechopen.100388 |
| الاتاحة: | http://hdl.handle.net/10261/280929 https://www.intechopen.com/books/10957 https://doi.org/10.5772/intechopen.100388 |
| Rights: | open |
| رقم الانضمام: | edsbas.EAFBB7BD |
| قاعدة البيانات: | BASE |
| ردمك: | 9781838819446 1838819444 |
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| DOI: | 10.5772/intechopen.100388 |