Thermal and Optical Properties of Multiblock Macrocycles with Hysteretic Polymorphic Transition
Thermal and Optical Properties of Multiblock Macrocycles with Hysteretic Polymorphic Transition
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具有滞后多晶型转变的多嵌段大环化合物的热学和光学性质
DOI：
10.1039/c7qm00621g
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发表时间：
2018
期刊：
影响因子：
--
通讯作者：
and Kazushi Kinbara
中科院分区：
文献类型：
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作者：
Kota Nabeya;Takahiro Muraoka;Norihisa Hoshino;Miho Aizawa;Takashi Kajitani;Tomoyuki Akutagawa;Atsushi Shishido;Takanori Fukushima;and Kazushi Kinbara
研究了由芳香族1,4-双(苯基乙炔基)苯(BPEB)组分和四乙二醇(TEG)链组成的大环分子1和2的热相变特性。 1和2是结构异构体，在BPEB单元与TEG链的连接点处差异较小，其中1的结构对称性低于2。1从各向同性液体冷却后形成晶体Cr1。图1中的Cr1显示了加热后产生Cr2的晶体到晶体的多晶型转变。由于 1 的 Cr1 到 Cr2 相变是一个放热过程，因此 Cr2 被认为在热力学上比 Cr1 更稳定。事实上，从 Cr2 冷却没有表现出相变，这种滞后多晶型转变允许在室温下制备不同晶态的 1，即 Cr1 和 Cr2。相反，2 显示了温度变化时晶体和向列相之间的可逆转变。基于1的多态性，还展示了作为记忆功能的光学特性的切换。因此，结构对称性低于2的分子结构可能是结晶及其热响应多晶型相变性能的重要因素。
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.