English   español  
Please use this identifier to cite or link to this item: http://hdl.handle.net/10261/109960
logo share SHARE   Add this article to your Mendeley library MendeleyBASE
Visualizar otros formatos: MARC | Dublin Core | RDF | ORE | MODS | METS | DIDL
Exportar a otros formatos:

Self-Association and Stereoselectivity in a Chiral Liquid-Crystal Colesteric Polymer Formed under Achiral Conditions

AuthorsPérez-Méndez, Mercedes ; Marsal Berenguel, Roser ; Garrido, Leoncio ; Martín-Pastor, Manuel
KeywordsCholesteric-liquid-crystal polyester
Stereoselective separation
Issue Date2003
PublisherAmerican Chemical Society
CitationMacromolecules 2003, 36, 8049-8055
AbstractA cholesteric, chiral, liquid-crystal polyester PTOBEE [C26H20O8]n, synthesized from the racemic mixture of their starting materials, showed an unexpected stereoselective separation of polymer units which incorporate a higher excess of one enantiomer at the expenses of the other when the polycondensation reaction products are decanted into a large excess of toluene. An NMR diffusion study of PTOBEE obtained for a sample with 67% enantiomeric excess (ee) showed the formation of a complex by self-association of several polymer units with an unexpected higher tendency of the complex to be formed when the sample is further diluted. Cross saturation transferred NMR experiments showed the high stability of this complex and provided evidence of slow exchange equilibrium with the single polymer unit. The results suggest that both effects, the enantiomeric excess obtained after decantation in toluene, which was higher in the second fraction of the precipitate, and the high tendency of the complex formation in diluted samples of this polymer could be related. Polymer units incorporating a certain excess of one of the enantiomers could result in a privileged spatial geometry of the substituents which favors its self- aggregation, resulting in its precipitation during the synthetic process at two different kinetic rates.
Appears in Collections:(ICTP) Artículos
Files in This Item:
File Description SizeFormat 
Macromolecules.pdf123,66 kBAdobe PDFThumbnail
Show full item record
Review this work

WARNING: Items in Digital.CSIC are protected by copyright, with all rights reserved, unless otherwise indicated.