端基含12个己氧基偶氮苯介晶基元的树状碳硅烷液晶的合成

Carbosilane Liquid Crystalline Dendrimer Containing Twelve 4-Hexyloxyazobenzene Mesogenic Groups

用发散法合成了周边含 1 2个己氧基偶氮苯介晶基元 ( M3 )端基的树状碳硅烷 ( D1 ) ,并用元素分析、氢谱、激光质谱、红外光谱、紫外 -可见光谱、偏光显微镜、DSC和 WAXD对产物进行表征 .结果表明 ,D1为向列相 ,与 M3相同 ,树状物相态由介晶基元相态决定 ,D1的液晶态相行为 :K92 N1 2 6I1 2 4N78K,D1熔点比 M3降低了 2 4～ 3 0℃ ,D1清亮点比 M3提高了 6～ 8℃ ,D1液晶态温区比 M3加宽 3 0～ 3 8℃ ,在树状物中观察到 S=+2的高强向错 .

The divergent synthesis of a new carbosilane liquid-crystalline(LC) dendrimer(D1) was described. Twelve 4-hexyloxyazobenzene groups (M3) were used as mesogenic fragments and attached to its periphery. Structure and properties of D1 were characterized by means of elemental analysis, 1H NMR, IR, UV, MALDI-TOF-MS, polarizing optical micrograph, DSC and WAXD. D1 is a nematic liquid crystal, which is the same as M3. The mesomorphic behaviour of the dendrimer depends on that of the mesogenic units. Phase behavior of D1 is K92N126I124N78K. m.p. of D1 is 24-30 ℃ lower than that of M3, its clearing temperature is 6-8 ℃ higher than that of M3 and its mesophase region is 30～38 ℃ wider than that of M3. The clearing enthalpy of D1 accords with the value that is commonly found for n-i phase transition in LC and LC polymers. This may be due to the deformation of branched dendrimer D1 which can be change to fit into the anisotropic LC phase structure. Eight extinguished brushes emanating from a stationary point are observed, corresponding to the high-strength disclination of S=+2 of dendrimer.