一类四臂液晶化合物的合成与相行为

Synthesis and Phase Behavior of a Kind of Four-Armed Liquid Crystals

以季戊四醇为中心,4-(正烷基酰氧基)-4′-苯甲酰氧基苯甲酸为液晶臂,经酯化反应合成一种芳香酯类星型四臂液晶化合物。通过元素分析、红外光谱、核磁共振谱测试技术对其分子结构进行表征。采用差示扫描量热、偏光显微分析、X射线衍射分析等测试技术对其液晶相行为进行研究。结果表明,随着端基柔性链的加长,tm、ti、tic及tc呈降低趋势,它们在液晶态时均呈现破碎焦锥及焦锥织构,属互变近晶相液晶,液晶区间较宽。其中升温时D1～D4的tm和ti值分别为92．3、80．6、68．3、51．1和159．2、145．1、127．5、109．8℃,液晶范围△t1在66．9～58．7℃之间,降温时的tic和tc值分别为138．6、127．4、111．6、99．1和57．1、52．6、42．0、31．8℃,液晶范围△t2在81．5～67．3℃之间。

A new class of star-shaped four-armed liquid crystals based on pentaerythfitol as a flexible core was synthesized by aromatic esterification. Their chemical structures were confirmed by means of elemental analysis, IR and ^1 H NMR characterizations, their mesomorphic properties and phase behavior were investigated by differential scanning calorimetry, polarizing optical microscopy and X-ray diffraction. The results show that tm, ti, tic and tc decreases as the carbon chain of the terminal groups increases. They displayed broken focal-conic and focal-conic texture in liquid crystal states, and had a w/de mesophase temperature range. The tm and ti of D1 -D4 were 92. 3 ℃, 80.6 ℃, 68.3 ℃, 51.1 ℃ and 159.2 ℃ , 145. 1 ℃, 127.5 ℃, 109.8 ℃ respectively, the mesogenic region Ah decreased from 66. 9 ℃ to 58.7 ℃ ; while the tic and tc were 138. 6 ℃, 127.4℃, 111.6 ℃, 99. 1 ℃ and 57. 1 ℃, 52.6 ℃, 42.0 ℃, 31.8 ℃ respectively, the mesogenic region △t2 decreased from 81.5 ℃ to 67. 3 ℃.