Van' t Hoff Laboratory for Physical and Colloid Chemistry, Utrecht University, Utrecht, The Netherlands.
J Phys Condens Matter. 2011 May 18;23(19):194110. doi: 10.1088/0953-8984/23/19/194110. Epub 2011 Apr 27.
We present small angle x-ray scattering data of single-domain nematic and columnar liquid crystal phases in suspensions of sterically stabilized gibbsite platelets. The measurements are performed with different sample orientations to obtain information about the three-dimensional structure of the liquid crystalline phases. With the x-ray beam incident along the director of the nematic phase a strong correlation peak is observed corresponding to the side-to-side interparticle correlations, which suggests a columnar nematic structure. Upon sample rotation this side-to-side correlation peak of the nematic shifts to higher Q-values, suggesting the presence of strong fluctuations of small stacks of particles with different orientations, while the overall particle orientation is constant. In the hexagonal columnar phase, clear Bragg intercolumnar reflections are observed. Upon rotation, the Q-value of these reflections remains constant while their intensity monotonically decreases upon rotation. This indicates that the column orientation fluctuates together with the particle director in the columnar phase. This difference between the behaviour of the columnar and the nematic reflections upon sample rotation is used to assign the liquid crystal phase of a suspension consisting of larger platelets, where identification can be ambiguous due to resolution limitations.
我们呈现了悬浮在稳定化 gibbsite 薄片中的单畴向列相和柱状液晶相的小角 X 射线散射数据。通过改变样品取向进行测量，以获取有关液晶相三维结构的信息。当 X 射线束沿向列相的指向器入射时，会观察到一个强相关峰，对应于颗粒间的侧向关联，这表明存在柱状向列结构。随着样品的旋转，向列相的侧向关联峰会向更高的 Q 值移动，这表明存在具有不同取向的小颗粒堆叠的强烈波动，而整体颗粒取向保持不变。在六方柱状相中，观察到明显的 Bragg 柱间反射。随着旋转，这些反射的 Q 值保持不变，而其强度随着旋转单调减小。这表明在柱状相中，柱取向与颗粒指向一起波动。这种样品旋转时柱状和向列反射行为的差异，用于对较大薄片组成的悬浮液的液晶相进行分配，由于分辨率的限制，这种分配可能存在歧义。
