Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, Daejeon, Republic of Korea.
J Phys Chem B. 2011 Jun 9;115(22):7314-20. doi: 10.1021/jp200882n. Epub 2011 May 13.
The phase behavior of HBC-C12 in p-xylene at various concentrations has been investigated by differential scanning calorimetry, polarized optical microscopy, small angle neutron scattering and wide-angle X-ray scattering techniques, and a phase diagram depending on concentration and temperature has been determined with detailed structural information. At room temperature, HBC-C12 in p-xylene forms needle-like crystalline aggregates with a rectangular columnar packing which is essentially the same as the crystalline phase of HBC-C12 in bulk. Upon heating, it undergoes two transitions, a transition from the rectangular columnar packing to another rectangular columnar packing with a small step change in the lattice parameter c, and then a transition to isotropic phase. In the isotropic phase, HBC-C12 molecules form stacked cylindrical particles which consist of ∼11-13 molecules depending on temperature. Upon cooling, HBC-C12 in p-xylene makes an abrupt transition from the isotropic to the rectangular columnar packing, which is in contrast with the gradual columnar to isotropic transition upon heating. These results provide important information for optimizing the conditions of discotic liquid crystal solution for the fabrication of DLC thin films using solution-processing techniques.
通过差示扫描量热法、偏光显微镜、小角中子散射和广角 X 射线散射技术研究了 HBC-C12 在对二甲苯中的相行为，确定了依赖于浓度和温度的相图，并获得了详细的结构信息。在室温下，HBC-C12 在对二甲苯中形成具有矩形柱状堆积的针状结晶聚集体，其基本上与块状 HBC-C12 的结晶相相同。加热时，它经历两个转变，一个是从矩形柱状堆积到晶格参数 c 略有变化的另一个矩形柱状堆积的转变，然后是向各向同性相的转变。在各向同性相中，HBC-C12 分子形成堆叠的圆柱形颗粒，其取决于温度由约 11-13 个分子组成。冷却时，HBC-C12 在对二甲苯中从各向同性相到矩形柱状堆积相发生突然转变，与加热时从柱状相到各向同性相的逐渐转变形成对比。这些结果为优化使用溶液处理技术制造 DLC 薄膜的盘状液晶溶液的条件提供了重要信息。
