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Morfología cuasicristalina dodecagonal en un terpolímero tetrabloqueado de poli
1Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA.
Journal of the American Chemical Society
|April 18, 2012
Resumen
Se descubrió una nueva morfología dodecagonal casi cristalina en un terpolímero tetrabloque de poliestireno-b-isopreno-b-estireno-b-óxido de etileno (SISO). Esta estructura única exhibe una simetría de rotación de 12 veces y se produce dentro de un rango de temperatura específico.
Área de la Ciencia:
- La ciencia de los polímeros es la ciencia de los polímeros.
- Ciencia de los materiales ciencia de los materiales.
- La cristalografía es una técnica de cristalografía.
Sus antecedentes:
- Los copolímeros de bloque se autoensamblan en nanoestructuras ordenadas.
- Las fases cuasicristalinas son raras en los polímeros sintéticos.
- Comprender la morfología del polímero es clave para las propiedades del material.
Objetivo del estudio:
- Para identificar y caracterizar una morfología dodecagonal cuasicristalina en un terpolímero tetrabloque SISO.
- Para determinar el rango de temperatura y las condiciones para la formación de QC.
- Para dilucidar la base molecular de este complejo empaque.
Principales métodos:
- Microscopía electrónica de transmisión (TEM) para la morfología de imágenes.
- Diseminación de rayos X de ángulo pequeño (SAXS) para el análisis estructural.
- Espectroscopia mecánica dinámica (DMS) para las transiciones térmicas.
Principales resultados:
- Se observó una morfología dodecagonal cuasicristalina (QC) en terpolímeros SISO.
- El estado QC existe entre las fases hexagonal (HEX) y sigma (σ).
- TEM reveló simetría de 12 veces sin orden de traslación de largo alcance.
Conclusiones:
- Los terpolímeros de tetrabloqueo SISO pueden formar estructuras dodecagonales casi cristalinas.
- La arquitectura molecular permite diversas simetrías de empaque.
- Este hallazgo amplía las morfologías conocidas en copolímeros de bloque.
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