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Arquitectura de polietileno quiral: desde hélices comprimidas/altamente dinámicas hasta hélices estiradas/cuasi

Rafael Rodríguez¹, Emilio Quiñoá¹, Ricardo Riguera¹

¹Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CIQUS) and Departamento de Química Orgánica Universidade de Santiago de Compostela , 15782 Santiago de Compostela, Spain.

Journal of the American Chemical Society

|July 16, 2016

Resumen

La modificación de polifenilacetilenos helicoidales (PPA) con diferentes enlaces o patrones de sustitución altera significativamente su estructura y dinámica. Los PPA para-sustituidos exhiben hélices dinámicas comprimidas que responden a los estímulos, a diferencia de los orto-sustituidos rígidos.

Área de la Ciencia:

Química de los polímeros
Química supramolecular
Ciencias de los materiales

Sus antecedentes:

Los polifenilacetilenos helicoidales (PPA) exhiben diversas propiedades influenciadas por la estructura monomérica.
La vinculación de grupos colgantes y los patrones de sustitución aromática son factores clave que afectan la conformación y la dinámica del PPA.

Objetivo del estudio:

Investigar el impacto del tipo de enlace (anilida, benzamida) y la sustitución aromática (orto, meta, para) en la estructura helicoidal y la dinámica del PPA.
Para correlacionar las modificaciones estructurales con los cambios en el carácter dinámico, la respuesta a los estímulos externos y el comportamiento de agregación.

Principales métodos:

Síntesis de dos series de APP con diferentes patrones de sustitución y tipos de enlace.
Caracterización integral utilizando técnicas como CD, UV-vis, Raman, NMR, DSC, TGA, rayos X, AFM y SEM en estado sólido y en solución.

Principales resultados:

Los PPA para-sustituidos (p-poly-1, p-poly-2) muestran hélices dinámicas comprimidas con una alta respuesta a los estímulos.
Los PPA meta-sustituidos (m-poly-1, m-poly-2) existen como un equilibrio de hélices comprimidas y estiradas, mostrando una dinámica reducida y una respuesta débil al estímulo.
El PPA orto-sustituido (o-poly-1) forma una hélice plana rígida y estirada que es inerte a los estímulos y propensa a la agregación.

Conclusiones:

El patrón de sustitución aromática controla críticamente la estructura helicoidal, la dinámica y la capacidad de respuesta del PPA.
El obstáculo estérico de los meta- y orto-sustitutos impide la acomodación del grupo colgante, lo que lleva a variaciones estructurales.
Comprender estas relaciones estructura-propiedad es crucial para el diseño de polímeros helicoidales funcionales.

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