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Estructuras de capas perforadas en copolímeros de bloque rod-coil de cristal líquido cristalino
Kishore K Tenneti1, Xiaofang Chen, Christopher Y Li
1A. J. Drexel Nanotechnology Institute and Department of Materials Science and Engineering, Drexel University, Philadelphia, PA 19104, USA.
Journal of the American Chemical Society
|November 3, 2005
Resumen
Los investigadores descubrieron nuevas capas perforadas tetragonales en copolímeros de bloque cristalino líquido (BCP, por sus siglas en inglés). Esta estructura única, observada en el bloque de poliestireno-2,5-bis[4-metoxifenilo]oxicarbonyl) estireno (PS-b-PMPCS), cambia los límites de fase debido al BCP.
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 rod-coil (BCP) exhiben comportamientos únicos de autoensamblaje.
- Los copolímeros de bloque cristalino líquido combinan propiedades de ambas cadenas de polímeros y cristales líquidos.
- Comprender la morfología BCP es crucial para el diseño de materiales avanzados.
Objetivo del estudio:
- Investigar el autoensamblaje y las características estructurales de los nuevos BCPs cristalinos líquidos de rod-coil.
- Para identificar y caracterizar la formación de estructuras de capas perforadas en el poliestireno (PS-b-PMPCS).
- Explorar la influencia del peso molecular y la composición en las morfologías observadas.
Principales métodos:
- Calorimetría de barrido diferencial (DSC) para el análisis térmico.
- Microscopía de luz polarizada (PLM) para la observación visual de las estructuras.
- Dispersión de rayos X de ángulo pequeño (SAXS) y difracción de rayos X de ángulo ancho (WAXD) para el análisis estructural.
- Microscopía electrónica de transmisión (TEM) para imágenes en el espacio real de morfologías.
Principales resultados:
- Se observó una nueva estructura tetragonal de capa perforada en PS-b-PMPCS.
- La formación de esta estructura dependía del peso molecular, apareciendo en diferentes composiciones para muestras de baja y alta M (w).
- La simetría de la perforación se identificó como tetragonal, desviándose del embalaje hexagonal típico.
- Se visualizó el "inicio" de la perforación, mostrando las etapas iniciales de la formación de la estructura.
- La mezcla con el homopolímero de poliestireno (PS) indujo perforaciones tetragonales uniformes en composiciones específicas.
Conclusiones:
- La naturaleza rod-coil del BCP influye significativamente en los desplazamientos de los límites de fase y las morfologías resultantes.
- Las capas perforadas tetragonales representan un nuevo motivo estructural en las BCPs cristalinas líquidas.
- El control de la composición, incluida la mezcla, ofrece una vía para adaptar las nanoestructuras BCP para aplicaciones avanzadas.
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