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Estudio espectroscópico de generación de frecuencia de suma visible por infrarrojos de la orientación molecular en
Gary P Harp1, Hasnain Rangwalla, Mohsen S Yeganeh
1Department of Polymer Science, The University of Akron, Akron, Ohio 44325, USA.
Journal of the American Chemical Society
|October 14, 2005
Resumen
La espectroscopia de generación de frecuencia de suma (SFG) reveló detalles moleculares en las interfaces de los polímeros. Las cadenas de alquilo en el acrilato polioctadecilo (PA-18) mostraron un aumento del desorden y la movilidad del grupo fenilo por debajo de la temperatura de transición de vidrio a granel.
Área de la Ciencia:
- La ciencia de los polímeros es la ciencia de los polímeros.
- Química de las superficies.
- La espectroscopia es una técnica de espectroscopia.
Sus antecedentes:
- Comprender la estructura interfacial del polímero es crucial para las propiedades del material.
- El poli (vinilo n-octadecilo carbamato-co-vinilo acetato) (PVNODC) y el poli (octadecilo acrilato) (PA-18) son polímeros con largas cadenas laterales de alquilo.
- El poliestireno (PS) es un polímero común utilizado en varias aplicaciones.
Objetivo del estudio:
- Para investigar la estructura molecular y la dinámica de PVNODC y PA-18 en las interfaces con el poliestireno.
- Para determinar la orientación y el orden de conformación de las cadenas de polímero.
- Para observar el impacto de la temperatura en el comportamiento de la interfaz.
Principales métodos:
- Espectroscopia de generación de frecuencia de suma visible infrarroja sensible a la superficie (SFG). espectroscopia de generación de frecuencia de suma visible infrarroja.
- Se empleó la geometría de reflexión interna total.
- Se llevaron a cabo estudios de temperatura variable.
Principales resultados:
- Los espectros SFG indicaron ángulos de inclinación del grupo metilo menores de 30 grados en las interfaces PVNODC/PS y PA-18/PS.
- Se observaron mayores defectos de gauche en las cadenas de alquilo PA-18 en la interfaz en comparación con la interfaz de aire.
- Una fuerte caída en la intensidad de SFG para ambos grupos fenilo PA-18 y PS se produjo cerca de la temperatura de fusión de PA-18, lo que indica la movilidad del grupo fenilo.
Conclusiones:
- El estudio aclara la estructura interfacial y la dinámica de PVNODC y PA-18 contra PS.
- La movilidad del grupo fenilo en la interfaz se demostró por debajo de la temperatura de transición de vidrio de PS a granel.
- Los hallazgos proporcionan información sobre el comportamiento interfacial del polímero y las transiciones de fase.
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