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Propiedades quirópticas de los copolímeros de poli (p-fenilenetinile) en películas delgadas: grandes valores de g
James N Wilson1, Winfried Steffen, Trent G McKenzie
1Department of Chemistry and Biochemistry, The University of South Carolina, Columbia, South Carolina 29208, USA.
Journal of the American Chemical Society
|June 13, 2002
Resumen
Los copolímeros de poli (p-fenilenetileno) sustituidos quiralmente exhiben una disimetría óptica significativa. Este efecto surge del ordenamiento supramolecular en hebras retorcidas y cristalinas, observadas a través del microscopio electrónico.
Área de la Ciencia:
- Química de Polímeros La Química de Polímeros es la química de los polímeros.
- Ciencia de los materiales Ciencia de los materiales.
- Espectroscopia Quiróptica Espectroscopia Quiróptica es la espectroscopia quiróptica que se utiliza para hacer espectroscopía.
Sus antecedentes:
- Los poli (p-fenilenetilenos) (PPEs) son conocidos por sus propiedades ópticas y electrónicas únicas.
- Los polímeros sustituidos quiralmente ofrecen potencial para aplicaciones ópticas avanzadas.
- El control del ensamblaje supramolecular es clave para ajustar las propiedades del polímero.
Objetivo del estudio:
- Para sintetizar copolímeros de poli (p-fenilenetinile) quiralmente sustituidos.
- Investigar la relación entre el contenido quiral y los efectos quirópticos.
- Para dilucidar la base estructural de las disimetrías ópticas observadas.
Principales métodos:
- La polimerización por metátesis de alquinos de monómeros específicos de dialquilo-dipropinilbenceno.
- Variando la proporción molar de los monómeros quirales a los achirales.
- Absorción óptica y espectroscopia de emisión para medir los efectos quirópticos (disimetría óptica).
- Microscopía electrónica de transmisión de campo oscuro para visualización estructural.
Principales resultados:
- Los copolímeros con un contenido de monómero quiral de 25-50 mol% mostraron grandes valores de disimetría óptica (g = -0.38 para la absorción, g = -0.19 para la emisión).
- La microscopía electrónica reveló el ordenamiento supramolecular en rasgos en cadena.
- Estas hebras exhibieron una estructura estriada, lo que sugiere la formación de cristalitos simples, torcidos quiralmente.
Conclusiones:
- Los EPI sustituidos quiralmente pueden lograr efectos quirópticos significativos a través de la polimerización controlada.
- El ensamblaje supramolecular en cristalitos retorcidos es responsable de las grandes disimetrías ópticas.
- Estos hallazgos abren caminos para el desarrollo de nuevos materiales ópticos quirales.
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