Département de Chimie, Université de Montréal , C.P. 6128, Succ. Centre-ville, Montreal, Québec H3C 3J7, Canada.
Langmuir. 2017 Jan 31;33(4):1084-1089. doi: 10.1021/acs.langmuir.6b04033. Epub 2017 Jan 13.
A mixture of a cholic acid dimer with a secondary amine group and formic acid at a molar ratio of 1/1 is regarded as an organic salt, and it self-assembles in aqueous solutions to form monodisperse nanofibers. The nanofibers are separated at low concentrations of the mixture but entangle with each other at high concentrations to form well-dispersed and randomly arranged 3D fibrous networks. Above the minimum gelation concentration of the dimer, the fibrous network is strong enough to gelate the aqueous solutions to form a hydrogel. Hydrogels obtained from the dimer salt at a lower concentration are isotropic and show extinction between crossed polarizers in the polarizing microscope, whereas they become anisotropic (i.e., nematic hydrogels) upon increasing the dimer salt concentration or under physical stirring. The parallel arrangement of nanofibers from randomly directed fibrous networks may be responsible for the formation of such nematic hydrogels.
一种摩尔比为 1/1 的胆酸二聚体、仲胺基团和甲酸的混合物被视为一种有机盐，它在水溶液中自组装形成单分散的纳米纤维。在混合物的低浓度下，纳米纤维分离，但在高浓度下相互缠绕，形成良好分散和随机排列的 3D 纤维网络。在二聚体的最低凝胶浓度以上，纤维网络足够强，可以使水溶液凝胶形成水凝胶。在较低浓度的二聚体盐中获得的水凝胶是各向同性的，在偏光显微镜下在正交偏振器之间显示消光，而当二聚体盐浓度增加或在物理搅拌下时，它们变成各向异性（即向列型水凝胶）。来自随机定向纤维网络的纳米纤维的平行排列可能是形成这种向列型水凝胶的原因。
