College of Chemistry & Environmental Science, Hebei University , Baoding, Hebei Province 071002, China.
Langmuir. 2013 Oct 8;29(40):12358-66. doi: 10.1021/la402836d. Epub 2013 Sep 26.
The liquid crystalline phase behavior and sol-gel transition in halloysite nanotubes (HNTs) aqueous dispersions have been investigated by applying polarized optical microscopy (POM), macroscopic observation, rheometer, small-angle X-ray scattering, scanning electron microscopy, and transmission electron microscopy. The liquid crystalline phase starts to form at the HNT concentration of 1 wt %, and a full liquid crystalline phase forms at the HNT concentration of 25 wt % as observed by POM and macroscopic observation. Rheological measurements indicate a typical shear flow behavior for the HNT aqueous dispersions with concentrations above 20 wt % and further confirm that the sol-gel transition occurs at the HNT concentration of 37 wt %. Furthermore, the HNT aqueous dispersions exhibit pH-induced gelation with more intense birefringence when hydrochloric acid (HCl) is added. The above findings shed light on the phase behaviors of diversely topological HNTs and lay the foundation for fabrication of the long-range ordered nano-objects.
通过应用偏光显微镜 (POM)、宏观观察、流变仪、小角 X 射线散射、扫描电子显微镜和透射电子显微镜，研究了埃洛石纳米管 (HNTs) 水溶液中的液晶相行为和溶胶-凝胶转变。通过 POM 和宏观观察发现，液晶相在 HNT 浓度为 1wt%时开始形成，在 HNT 浓度为 25wt%时形成完全的液晶相。流变测量表明，浓度高于 20wt%的 HNT 水溶液具有典型的剪切流动行为，并进一步证实溶胶-凝胶转变发生在 HNT 浓度为 37wt%时。此外，当加入盐酸 (HCl) 时，HNTs 水溶液表现出 pH 诱导的胶凝，表现出更强的双折射。上述发现揭示了不同拓扑结构的 HNTs 的相行为，为制备长程有序的纳米物体奠定了基础。
