Barberá Joaquín, Bardají Manuel, Jiménez Josefina, Laguna Antonio, Martínez M Pilar, Oriol Luis, Serrano José Luis, Zaragozano Irene
Polymer and Liquid Crystal Group--Departamento de Química Orgánica, Instituto de Ciencia de Materiales de Aragón, Universidad de Zaragoza-C.S.I.C., 50009 Zaragoza, Spain.
J Am Chem Soc. 2005 Jun 29;127(25):8994-9002. doi: 10.1021/ja051042w.
A synthetic strategy has been developed to prepare cyclotriphosphazenes that bear polycatenar aromatic esters as promesogenic units linked to phosphorus atoms. The microsegregation of the rigid and flexible parts of the system and the space-filling properties are the driving forces that determine the kind of mesomorphism exhibited by the organocyclotriphosphazenes. Mesogenic units that contain only one terminal alkyl chain give rise to calamitic mesomorphism, since the molecules are arranged to give a cylindrical superstructure with the aromatic promesogenic cores elongated in a manner approximately perpendicular to the cyclotriphosphazene ring. On the other hand, mesogenic units that contain three long terminal chains exhibit columnar mesophases. In this case, a discotic structure consisting of promesogenic cores arranged approximately parallel to the cyclotriphosphazene ring can explain the columnar organization. The X-ray diffraction patterns corresponding to the Col(h) mesophase of the cyclotriphosphazene with dodecyloxy chains (8) indicate the presence of helical ordering, which was confirmed for a homologous compound bearing stereogenic centers on two of the terminal chains (11). All of the synthesized phosphazenes show a high thermal stability.
已开发出一种合成策略来制备环三磷腈，该环三磷腈带有作为前介晶单元与磷原子相连的多链状芳族酯。体系中刚性和柔性部分的微相分离以及空间填充性质是决定有机环三磷腈呈现的介晶类型的驱动力。仅含有一个末端烷基链的介晶单元会产生向列型介晶现象，因为分子排列形成圆柱形超结构，其中芳族前介晶核以近似垂直于环三磷腈环的方式伸长。另一方面，含有三个长末端链的介晶单元呈现柱状介相。在这种情况下，由近似平行于环三磷腈环排列的前介晶核组成的盘状结构可以解释柱状排列。对应于带有十二烷氧基链的环三磷腈（8）的Col(h)介相的X射线衍射图谱表明存在螺旋有序，这在两个末端链上带有手性中心的同系物（11）中得到了证实。所有合成的磷腈都表现出高的热稳定性。
