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Thermal and optical properties of multiblock macrocycles with hysteretic polymorphic transition

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Abstract

The thermal phase transition properties of macrocyclic molecules 1 and 2 consisting of aromatic 1,4-bis(phenylethynyl)benzene (BPEB) components and tetraethylene glycol (TEG) chains were investigated. 1 and 2 are structural isomers with a small difference at the connecting points of the BPEB units with TEG chains, where 1 has a lower structural symmetry than 2. 1 forms a crystal Cr1 upon cooling from the isotropic liquid. 1 at Cr1 shows a crystal-to-crystal polymorphic transition upon heating affording Cr2. Since the Cr1-to-Cr2 phase transition of 1 is an exothermic process, Cr2 is considered to be thermodynamically more stable than Cr1. Indeed, cooling from Cr2 shows no phase transition, and this hysteretic polymorphic transition allows the preparation of 1 in different crystalline states, namely Cr1 and Cr2, at room temperature. In contrast, 2 shows a reversible transition between a crystal and a nematic phase upon temperature changes. Based on the polymorphism of 1, switching of an optical property as a memory function is also demonstrated. Thus, the molecular structure of 1 with a lower structural symmetry than that of 2 is likely an important factor for the crystallization and its thermoresponsive polymorphic phase transition property.

Graphical abstract: Thermal and optical properties of multiblock macrocycles with hysteretic polymorphic transition

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Publication details

The article was received on 30 Dec 2017, accepted on 21 Feb 2018 and first published on 22 Feb 2018


Article type: Research Article
DOI: 10.1039/C7QM00621G
Citation: Mater. Chem. Front., 2018, Advance Article
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    Thermal and optical properties of multiblock macrocycles with hysteretic polymorphic transition

    K. Nabeya, T. Muraoka, N. Hoshino, M. Aizawa, T. Kajitani, T. Akutagawa, A. Shishido, T. Fukushima and K. Kinbara, Mater. Chem. Front., 2018, Advance Article , DOI: 10.1039/C7QM00621G

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