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La preparación y el pH desencadenaron la inversión de las vesículas de poli (ácido acrílico) -bloque de
1Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec, Canada H3A 2K6.
Journal of the American Chemical Society
|December 5, 2003
Resumen
Se investigó el comportamiento sensible al pH de los copolímeros triblock. A un pH bajo, las cadenas P4VP forman la capa externa de las vesículas, mientras que a un pH alto, las cadenas PAA forman la capa externa, lo que demuestra la morfología del agregado sintonizable.
Área de la Ciencia:
- La ciencia de los polímeros es la ciencia de los polímeros.
- Ciencia de los materiales Ciencia de los materiales.
- Química supramolecular de las moléculas.
Sus antecedentes:
- Los copolímeros de tribloqueo bianfifílico exhiben un comportamiento complejo de autoensamblaje.
- El pH es un factor crítico que influye en las interacciones de la cadena de polímeros y la formación de agregados.
Objetivo del estudio:
- Para investigar las morfologías agregadas dependientes del pH de un copolímero tribloqueante PAA-b-PS-b-P4VP.
- Comprender el papel de la repulsión en cadena inducida por el pH en la estabilización de diferentes estructuras agregadas.
Principales métodos:
- Microscopía Electrónica de Transmisión (TEM) para el análisis de la morfología.
- Medidas del potencial Zeta para la caracterización de la superficie.
- Variación sistemática del pH en las mezclas de disolventes DMF/THF/H2O.
Principales resultados:
- Las transiciones de la morfología agregada de las vesículas (pH 1) a los agregados sólidos (pH 3-11) y de vuelta a las vesículas (pH 14).
- La composición de la superficie de la vesícula se invierte con el pH: P4VP en el exterior a pH 1, PAA en el exterior a pH 14.
- Inversión reversible de la composición de la superficie de la vesícula (PAA a P4VP en el exterior) lograda por el cambio de pH.
Conclusiones:
- La morfología agregada y la composición de la superficie están dictadas por las repulsiones entre cadenas dependientes del pH.
- Los cambios morfológicos e inversiones observados se atribuyen a las interacciones electrostáticas dentro de las coronas de polímeros.
- La inversión reversible de las vesículas sugiere un mecanismo de vesículas enteras en lugar de un reensamblaje de una sola cadena.
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