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Issue 5, 2018
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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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Article information


Submitted
30 Dec 2017
Accepted
21 Feb 2018
First published
22 Feb 2018

Mater. Chem. Front., 2018,2, 969-974
Article type
Research Article

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, 2, 969
DOI: 10.1039/C7QM00621G

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