A systematic study on the influences of linkage length on phase behaviours and charge carrier mobilities of discotic dimers. Issue 2 (26th January 2017)

• Record Type: Journal Article
• Authors: Wang, Jianchuang; Zhang, Chunxiu; Zhang, Shuaifeng; Hao, Xingtian; Hong, Feng; Zhang, Ao; Wang, Yi-Fei; Wu, Hao; Zhang, Wanying; Pu, Jia-Ling
• Is Part Of: Liquid crystals. Volume 44:Issue 2(2017)
• Page Start: 394
• Page End: 404
• Publication Date: 2017-01-26
• Subjects: Discotic liquid crystal (LC) -- discotic dimer -- triphenylene -- perfect twin -- columnar phase; Liquid crystals -- Periodicals; 548.905
• DOI: 10.1080/02678292.2016.1213324
• Languages: English
• ISSNs: 0267-8292

Abstract

ABSTRACT: Two series of discotic dimersT3Dn andT5Dn 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 colhp phase to colh phase, namely dimersT3Dn ( n = 6–12) based onHAT3 exhibiting a single colhp phase, dimersT4Dn ( n = 6, 7, 11, 12) based onHAT4 showing a highly ordered colhp phase in low-temperature region and a colh phase in high-temperature region, dimersT4Dn ( n = 8–10) based onHAT4 displaying a single colhp phase and dimersT5Dn ( n = 6–11) based onHAT5 indicating a single colh phase. DimersT4Dn showed a phase competition between colh phase and colhp 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. Graphical Abstract: