Abdel-Rahem R, Gradzielski M, Hoffmann H
Chemistry Department, College of Science, University of Almrgeb, Alkhoms, Libya.
J Colloid Interface Sci. 2005 Aug 15;288(2):570-82. doi: 10.1016/j.jcis.2005.03.040.
The phase behavior of 2-hydroxy-1-naphthoic acid (2,1-HNC) mixed with cetyltrimethylammonium hydroxide (CTAOH) is reported. This novel system is compared with the published one of 3-hydroxy-2-naphthoic acid (3,2-HNC) mixed with CTAOH. We investigated the phase behavior and properties of the phases in aqueous solutions of 100 mM CTAOH with 2,1-HNC. In both systems a multilamellar vesicle phase is formed when the naphthoate/surfactant ratio (r) reaches unity. When an increasing amount of 2,1-HNC is mixed with a micellar solution of 100 mM CTAOH, an isotropic low-viscous micellar solution, a viscoelastic gel (consisting of rodlike micelles), a turbid region (two-phase region), and a viscoelastic liquid crystalline gel (consisting of multilamellar vesicles, MLV) were formed. The vesicular phase is highly viscoelastic and has a yield stress value. The transition from the micellar to the vesicle phase occurs for CTAOH/2,1-HNC over a two-phase region, where micelles and vesicles coexist. Also it was noticed that 2,1-HNC is dissolved in 100 mM CTAOH until the naphthoate/surfactant ratio reaches approximately 1.5, and the liquid crystalline phases were found to change their color systematically when they were viewed between two crossed polarizers. The vesicles have been characterized by differential interference contrast microscopy, freeze-fracture electron microscopy, and cryo-electron microscopy (cryo-TEM). The vesicles were polydisperse and their diameter ranged from 100 to 1000 nm. The interlamellar spacing between the bilayers was determined with small angle neutron scattering and agrees with the results from different microscopical methods. The complex viscosity rises by six orders of magnitude when rodlike micelles are formed. The complex viscosity decreases again in the turbid region, and then rises approximately six orders of magnitude above the water viscosity. This second rising is due to the formation of the liquid crystalline MLV phase.
报道了2-羟基-1-萘甲酸（2,1-HNC）与十六烷基三甲基氢氧化铵（CTAOH）混合体系的相行为。将该新型体系与已发表的3-羟基-2-萘甲酸（3,2-HNC）与CTAOH的混合体系进行了比较。我们研究了100 mM CTAOH与2,1-HNC的水溶液中的相行为和各相的性质。在这两个体系中，当萘甲酸盐/表面活性剂比（r）达到1时，都会形成多层囊泡相。当将越来越多的2,1-HNC与100 mM CTAOH的胶束溶液混合时，会形成各向同性的低粘度胶束溶液、粘弹性凝胶（由棒状胶束组成）、浑浊区域（两相区域）和粘弹性液晶凝胶（由多层囊泡，MLV组成）。囊泡相具有高粘弹性且具有屈服应力值。CTAOH/2,1-HNC在两相区域内发生从胶束相到囊泡相的转变，在此区域胶束和囊泡共存。还注意到，2,1-HNC溶解于100 mM CTAOH中，直到萘甲酸盐/表面活性剂比达到约1.5，并且当在两个正交偏振器之间观察时，发现液晶相的颜色会系统地变化。通过微分干涉对比显微镜、冷冻断裂电子显微镜和冷冻电子显微镜（冷冻透射电子显微镜，cryo-TEM）对囊泡进行了表征。囊泡是多分散的，其直径范围为100至1000 nm。通过小角中子散射确定了双层之间的层间距，其与不同显微镜方法的结果一致。当形成棒状胶束时，复数粘度上升六个数量级。在浑浊区域复数粘度再次降低，然后在高于水粘度的情况下上升约六个数量级。这第二次上升是由于液晶MLV相的形成。
