Synthesis of New Triphenylene-containing Discotic Liquid Crystals and the Influence of Fluorophilic Effect and Molecular Symmetry on Mesomorphism

✍ Scribed by Zhao Ke-Qing; Wang Bi-Qin; Hu Ping; Li Quan; Zhang Liang-Fu

• Publisher: John Wiley and Sons
• Year: 2005
• Tongue: English
• Weight: 153 KB
• Volume: 23
• Category: Article
• ISSN: 0256-7660
• DOI: 10.1002/cjoc.200590767

✦ Synopsis

New symmetrical and asymmetrical triphenylene-containing discotic liquid crystals with two different peripheral alkyl chains, known as sym-TP(OC 6 H 13 ) 3 (OR) 3 and asym-TP(OC 6 H 13 ) 3 (OR) 3 , were synthesized. Their thermotropic liquid crystal properties were investigated through polarizing optical microscopy (POM), differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analyses. The asymmetrical discogens are 2,6,11trialkoxy-3,7,10-trihexyloxytriphenylenes, with the alkyl chain carbon numbers varying from 3-10, 12, and 14, while the symmetrical compounds are 2,6,10-trialkyloxy-3,7,11-trihexyloxytriphenylene. Two fluoroalkoxy substituted triphenylene discogens, 2,6,10-tri(4,4,4-trifluorobutoxy)-3,7,11-trihexyloxytriphenylene and its asymmetrical isomer 2,6,11-tri(4,4,4-trifluorobutoxy)-3,7,10-trihexyloxytriphenylene were prepared. These two compounds show higher melting and clearing points than their alkoxy analogs, which implies that fluorophilic effect exists in the formation and stabilization of discotic columnar mesophase. The triphenylene derivatives TP(OC 6 H 13 ) 3 (OR) 3 with two different peripheral chains, symmetrically or asymmetrically attached on triphenylene cores, have lower melting points and clearing points than those of the higher symmetrical compounds TP(OR) 6 with the same total chain carbon numbers. The mixed-chain-triphenylenes with longer alkoxy chains (n＝9, 10, 12, 14) show columnar mesophase at room temperature.