1,3-双[4-(4'-甲基)-氧化偶氮苯基-苯氧羰基]苯氧甲基-1,1,3,3-四甲基二硅氧烷的合成、晶体结构和液晶性能

合成了[CH3(C6H4)N2O(C6H4)COO(C6H4)OCH2Si(CH3)2]2O,经IR,1^HNMR和元素分析表征,并测定其单晶结构。结果表明,晶体属单斜晶系,空间群为P21/c,晶胞参数a=1.7557(1),b=1.0938(9),c=2.3300(1)nm,β=105.6(6)°,V=4.3116nm^3,Mr=855.07,Z=4,Dc=1.317g/cm^3,μ(CuKα)=6.335cm^-1,F(000)=900,最终的偏离因子R=0.0837,Rw=0.0913。该分子中,柔性的四甲基二硅氧烷嵌段与氧化偶介晶基团形成ABA结构齐聚物。两条刚性的介晶基链节的轴向几乎平行向上伸出。径长比(L/D)为4.23.该液晶化合物的要变温度K174.4N226.8Ⅰ.通过结构分析,讨论了该类化合物的结构对液晶相变行为的影响。

Synthesis, crystal structure and liquid crystal properties of 1,3-Di- [4-(4'-methyl)-azoxybenzene-benzoxycarbonyl] benzoxymethyl- 1,1,3,3- tetramethylisiloxane

The title compound [CH3(C6H4)N2O(C6H4)COO(C6H4)OCH2Si (CH3)2]2O was synthesized and characterized by IR,1^H NMR and elemental analysis. The crystal structure was determined by single crystal X-ray diffraction techniques. The crystal belongs to the monoclinic space group P21/c with a=1.7557(1), b=1.0938(9), c=2.3300(1)nm, β=105.6(6) °, V=4.3116 nm^3, Mr=855.07, Z=4, Dc=1.317 g/cm^3, μ=6.335 cm^-1, F (000)=900. Final R=0.0837, Rw=0.0913 . The flexible group of tetramethylsiloxane and the rigid azoxybenzene functinality form a neat-polymer of ABA structure, in which the two rigid mosomorphic chain shafts are parallelt to each other with L/D=4.23. The phase changing parametters of the liquid crystal are K 174.4N 226.8 Ⅰ. The relationship between the structure and phase changing behavior of the liquid crystal of this kind of compounds is also discussed.