A systematic study on the influences of linkage length on phase behaviours and charge carrier mobilities of discotic dimers

作者：Wang, Jianchuang; Zhang, Chunxiu^*; Zhang, Shuaifeng; Hao, Xingtian; Hong, Feng; Zhang, Ao; Wang, Yi-Fei; Wu, Hao; Zhang, Wanying; Pu, Jia-Ling

来源：Liquid Crystals, 2017, 44(2): 394-404.

DOI：10.1080/02678292.2016.1213324

• Discotic liquid crystal (LC)
• discotic dimer
• triphenylene
• perfect twin
• columnar phase

Two series of discotic dimers T3Dn and T5Dn based on hexapropoxytriphenylene (HAT3) and hexapentyloxytriphenylene(HAT5), respectively, with polymethylene linkage O(CH2)(n)O (n=3-12) have been synthesised. Their mesomorphism was investigated by differential scanning calorimetry, polarising optical microscopy and X-ray diffraction. The results showed that side chains induced a phase transition from col(hp) phase to col(h) phase, namely dimers T3Dn (n=6-12) based on HAT3 exhibiting a single col(hp) phase, dimers T4Dn (n=6, 7, 11, 12) based on HAT4 showing a highly ordered col(hp) phase in low-temperature region and a col(h) phase in high-temperature region, dimers T4Dn (n=8-10) based on HAT4 displaying a single col(hp) phase and dimers T5Dn (n=6-11) based on HAT5 indicating a single col(h) phase. Dimers T4Dn showed a phase competition between col(h) phase and col(hp) phase induced by linkages. Surprisingly, a unique phenomenon was found by us, that is, those compounds in which linkage lengths were twice those of side chains showed the largest enthalpies, the smallest intracolumnar spacings and the highest charge-carrier mobilities among their homologues, respectively, which implied that they formed the most highly ordered phase among their homologues.
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• 出版日期2017-1
• 单位北京印刷学院