Substituted Septithiophenes with End Groups of Different Size: Packing and Frustration in Bulk and Thin Films.
Langmuir
; 32(6): 1533-41, 2016 Feb 16.
Article
em En
| MEDLINE
| ID: mdl-26807677
ABSTRACT
We report on three different liquid crystalline compounds with a central septithiophene core and alkylated end groups of strongly increasing bulkiness. In principle, the thiophene cores prefer to pack parallel to optimize their π-π interactions, which becomes sterically impossible for the bulkier end groups. Using X-ray diffraction, we find that the way out of this packing dilemma is toward liquid-crystal phases of higher dimensionality in the order smectic â columnar â bicontinuous cubic. For the smectic phase, packing in a monolayer is no problem; for the other ones packing considerations become more stringent in films due to the boundaries. Surface X-ray techniques and atomic force microscopy indicate an appreciable difference between monolayer and three-layer films, in which the monolayers appear to escape from packing frustration by generating superstructures. We propose a basic structure of columns parallel to the substrate that provides a compromise between preserving some π-π interactions and packing the bulky alkyl groups.
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Bases de dados:
MEDLINE
Idioma:
En
Revista:
Langmuir
Assunto da revista:
QUIMICA
Ano de publicação:
2016
Tipo de documento:
Article
País de afiliação:
Alemanha