Unique Monotropic Phase Transition Behaviors of a Butterfly-Shaped Diphenylpyrimidine Molecule

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• 作者：Minwook Park ; Yu-Jin Choi ; Dae-Yoon Kim ; Seok-Ho Hwang ; Kwang-Un Jeong
• 刊名：Crystal Growth & Design
• 出版年：2015
• 出版时间：February 4, 2015
• 年：2015
• 卷：15
• 期：2
• 页码：900-906
• 全文大小：377K
• ISSN：1528-7505

文摘

The physical properties of two-dimensional disc-shaped aromatic carbon molecules strongly depend on the molecular packing structures. A butterfly-shaped diphenylpyrimidine molecule (DPP-6C12) was synthesized by covalently attaching two tridodecyl benzoate tails (6C12) at the both sides of the diphenylpyrimidine (DPP) moiety. Unique phase transition behaviors of DPP-6C12 and their origins were investigated with the combined techniques of thermal, scattering, spectroscopic, and microscopic analyses. On the basis of the experimental results and analyses, it was realized that a butterfly-shaped DPP-6C12 formed three ordered phases: a plastic crystal phase (PK), a crystal phase (K), and a liquid crystal phase (桅). By breaking the molecular symmetry and coplanarity of DPP-6C12, peculiar monotropic phase transition behaviors were observed. The stable 桅 mesophase was formed either by a slow heating above the metastable PK phase or by an isothermal annealing between T_桅 and T_K. The stable K phase was only formed by a slow heating from the preordered 桅 mesophase, and the formation of the K phase directly from the isotropic state (I) was forbidden because the nucleation barrier from I to K was too high to be overcome via thermal annealing.