摘要
用发散法合成周边含 12个丁氧基偶氮苯介晶基元(M5 )端基新的一代树状碳硅烷(D1).并用元素分析、核磁共振、激光解吸电离飞行时间质谱、红外、紫外、偏光显微镜、差示扫描量热(DSC)和广角X射线衍射(WAXD)表征.D1为向列相与M5相同,树状物相态由介晶基元相态决定,D1相行为:K82N13 3I13 2N67K,D1熔点比M5降低 3 0～ 43℃,D1清亮点比M5增加 9～ 11℃,D1介晶相区比M5加宽 3 9～ 5 4℃,观察到 8条黑刷的树状物的高强向错(S =+ 2),D1清亮焓值略低于通常液晶n i相变清亮焓值。
The divergent synthesis of a new carbosilane liquid-crystalline (LC) dendrimer of the first generation (D1) is described. Twelve 4-butoxyazobenzene groups are used as mesogenic fragments and attached in the periphery of the molecule. Structure and properties of D1 were characterized by element analysis, 1H NMR, MALDI-TOF-MS, IR, UV-Vis, polarizing optical micrograph, DSC and WAXD. It is argued that mesophase of nematic type is realized. It is shown that the mesophase type of the dendrimer essentially depends on the chemical nature of the mesogenic groups. Phase behavior of D1 is K82N133I132N67K. The melting point of D1 is 30～43 ℃ lower than that of M5, its clearing temperature is 9～11 ℃ higher than that of M5 and its mesophase region is enlarged by 39～54 ℃ compared to that of M5. Eight extinguished brushes emanating from a stationary point are observed, corresponding to the high-strength disclination of S=+2 of dendrimer. The clearing enthalpy of D1 is smaller than the value that is commonly found for phase transition n-i in LC and LC polymers. This may be due to the presence of branched dendrimer cores which cannot be easily deformed to fit into the anisotropic LC phase structure.
出处
《化学学报》
SCIE
CAS
CSCD
北大核心
2002年第12期2232-2237,共6页
Acta Chimica Sinica
基金
国家自然科学基金(Nos.2 98740 2 0
5 95 730 2 9)资助项目
