Effects of Particle Modification on Properties of Particle/Liquid-Crystal Composites
Effects of Particle Modification on Properties of Particle/Liquid-Crystal Composites
复制标题
颗粒改性对颗粒/液晶复合材料性能的影响
DOI：
10.1080/15421400490435747
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发表时间：
2004
影响因子：
0.7
通讯作者：
H. Yokoyama
中科院分区：
文献类型：
--
作者：
T. Yamamoto;M. Yada;H. Yokoyama
通过偏光显微镜和流变学研究了粒子改性对粒子/液晶复合材料物理性能的影响。用偶氮苯羧酸（8AB 5COOH）在丙酮中对颗粒（ZrO 2）进行表面改性。表面覆盖率评估为56%。在偏光显微镜下观察到，经表面改性后的8AB 5COOH-ZrO 2/8 CB复合材料在近晶A（SmA）相和近晶N（N）相均呈现出特有的织构。通过改变相结构（SmA ParticipN）可以反复观察到这些纹理，表明颗粒表面和8 CB分子之间存在强耦合。在8AB_5COOH-ZrO_2/8 CB复合材料的流变学测试中，我们观察到了与各向同性→ N相变相关的稳态剪切粘度的协同变化。随着颗粒浓度的增加，虽然42°C附近粘度的固有不连续变化变小，但在46°C附近出现了粘度的新特征变化并成为主导。剪切速率对这些变化的影响表明，结构化区域可以与改性颗粒一起形成。46°C左右的粘度变化可归因于8 CB与结构化区域中颗粒表面的相变行为。此外，该系统的形态可以可逆地调制与援助的偶氮苯部分的异构化。
We investigated effects of particle modification on physical properties of particle/liquid-crystal composites by polarizing optical microscopy and rheology. The surface modification of particles (ZrO2) was performed with an azobenzene carboxylic acid (8AB5COOH) in acetone. Surface coverage was evaluated as 56%. Under a polarizing microscope, the composites containing the surface-modified particle (8AB5COOH-ZrO2/8CB) exhibited characteristic textures in both smectic A (SmA) and nematic (N) phases. These textures could be observed repeatedly by changing the phase structures (SmA ↔ N) indicating the presence of strong coupling between the particle surface and 8CB molecules. In the rheological measurements, we observed cooperative changes of steady shear viscosity associated with isotropic → N phase transition in 8AB5COOH-ZrO2/8CB composites. With increasing the particle concentration, although the inherent discontinuous change of the viscosity around 42°C became small, a new characteristic change in the viscosity appeared around 46°C and became dominant. Effects of the shear rates on these changes suggest that structured regions may be formed with the modified particles. The viscosity change around 46°C would be attributable to the phase transition behavior of 8CB coupled with the particle surface in the structured regions. In addition, the morphology of the system can be reversibly modulated with the aid of the isomerization of the azobenzene moieties.