Miscibility Between Differently-Shaped Mesogens: Structural and Morphological Study of a Phthalocyanine-Perylene Binary System

Abstract : The thermotropic, structural, and morphological properties of blends of a disk-like liquid crystalline phthalocyanine derivative and a lath-shaped perylenetetracarboxidiimide mesogen derivative have been studied by combining differential scanning calorimetry, thermal polarized optical microscopy, X-ray diffraction, solidstate nuclear magnetic resonance, and atomic force microscopy. The two compounds are fully miscible for blends containing at least 60 mol % of the disk-like molecule. In such composition range, the homogeneous blends form a columnar hexagonal (Colh) mesophase for which the thermal stability is enhanced compared to that of the corresponding mesophase of the pure phthalocyanine. The miscible blends self-align homeotropically between two glass slides. For blends containing between 55 and 40 mol % of the diskshaped molecule, the two components are fully miscible at high temperature but the perylene derivative forms a separate crystalline phase when the temperature is decreased. Phase separation is systematically observed in blends containing less than 40 mol % of the discotic molecule. In this case, the resulting Colh mesophase is less stabilized compared to the blends containing a larger amount of the phthalocyanine derivative. These phase-separated blends do not show any homeotropic alignment. AFM investigations confirm the formation of a single columnar morphology in the phthalocyanine-rich blends, consistent with the full miscibility between the two compounds. Solid-state NMR measurements on the mixed phase show the influence of the presence of the perylene molecules on the molecular dynamics of the molecules; remarkably, the presence of the host molecules improves the local order parameter in the phthalocyanine columnar phase.
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https://hal-polytechnique.archives-ouvertes.fr/hal-00843066
Contributor : Gaël Zucchi <>
Submitted on : Wednesday, July 10, 2013 - 1:16:49 PM
Last modification on : Wednesday, April 3, 2019 - 1:19:22 AM

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Gaël Zucchi, Pascal Viville, Bertrand Donnio, Alexandru Vlad, Sorin Melinte, et al.. Miscibility Between Differently-Shaped Mesogens: Structural and Morphological Study of a Phthalocyanine-Perylene Binary System. Journal of Physical Chemistry B, American Chemical Society, 2009, 113 (16), pp.5448. ⟨10.1021/jp809591h⟩. ⟨hal-00843066⟩

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