LIQUID CRYSTALLINE BEHAVIOR OF OCTYLCYANOBIPHENYL CONFINED TO SUBMICRON-SIZE RANDOMLY CONNECTED POROUS GLASSES
LIQUID CRYSTALLINE BEHAVIOR OF OCTYLCYANOBIPHENYL CONFINED TO SUBMICRON-SIZE RANDOMLY CONNECTED POROUS GLASSES
复制标题
亚微米随机连接多孔玻璃中辛基氰基联苯的液晶行为
DOI：
10.1103/physreve.56.554
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发表时间：
1997
影响因子：
2.4
通讯作者：
F. Aliev
中科院分区：
文献类型：
--
作者：
G. Iannacchione;S. Qian;D. Finotello;F. Aliev
本文报道了用重水核磁共振和高分辨交流量热法研究辛基氰基联苯~8CB！限制为随机取向和相互连接的大孔~1000？平均孔径！和微孔~100°平均孔径！戴眼镜。在大孔玻璃中，向列相到各向同性(N-I)的相变保持了块状的弱一级性质。向列相由核磁共振粉末花样谱表征，正如没有优选空间方向的指向矢分布所预期的那样，它与类各向同性成分共存。取向有序度略低于块体取向有序度，近晶相开始时，取向有序度没有突然增加，表明向列相和近晶相之间的耦合较弱。此外，由于约束尺寸的限制，近晶A向向列相的转变被相当大的抑制和加宽。在微孔玻璃中，取向有序行为与Vycor玻璃的取向有序行为相似。没有检测到相变，而是局域取向有序的连续演化。孔间和孔内相互作用很重要。@S1063-651X~97 02507-5#
We report a study of the orientational order via deuterium NMR and high resolution ac calorimetry on octylcyanobiphenyl ~8CB! confined to randomly oriented and interconnected macroporous ~1000 Å mean pore size! and microporous~100 Å mean pore size ! glasses. In the macroporous glass, the nematic to isotropic (N-I ) phase transition retains the bulklike weakly first order nature. The nematic phase is characterized by an NMR powder pattern spectra, as expected for a director distribution with no preferred spatial direction, and it coexists with an isotropiclike component. The orientational order is slightly suppressed from the bulk’s and there is no sudden increase in orientational order due to the onset of the smectic phase suggesting a weaker coupling between nematic and smectic order parameters. Further, due to the confining size, the smecticA to nematic transition is considerably suppressed and broadened. In the microporous glass, the orientational order behavior is reminiscent of that in Vycor glass. No phase transitions are detected, rather, there is a continuous evolution of local orientational order. Interporous and intraporous interactions are important. @S1063-651X~97!02507-5#