Self-Assembly in Systems of Didodecyldimethylammonium Surfactants: Binary and Ternary Phase Equilibria and Phase Structures with Sulphate, Hydroxide, Acetate, and Chloride Counterions
Self-Assembly in Systems of Didodecyldimethylammonium Surfactants: Binary and Ternary Phase Equilibria and Phase Structures with Sulphate, Hydroxide, Acetate, and Chloride Counterions
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双十二烷基二甲基铵表面活性剂体系中的自组装：二元和三元相平衡以及硫酸盐、氢氧化物、乙酸盐和氯离子抗衡离子的相结构
DOI：
10.1006/jcis.1993.1102
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发表时间：
1993
期刊：
影响因子：
--
通讯作者：
A. Khan
中科院分区：
文献类型：
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作者：
C. Kang;A. Khan
通过水氘核核磁共振和偏光显微镜方法研究了四种二元（温度与组成）表面活性剂体系二十二烷基二甲基铵硫酸盐（DDAS）、氢氧化物（DDAOH）、乙酸盐（DDAAc）和氯化物（DDAC）与水和一种等温三元体系（DDAS-水-十二烷）的相平衡。 DDAS 和 DDAC 表面活性剂在 298 K 时几乎不溶于水（约 3.5 × 10-3 m DDAS 和约 1.4 × 10-2 m DDAC）（m，每千克水表面活性剂的摩尔数），但它们在水中膨胀，各自产生层状液晶相。另一方面，DDAOH 和 DDAAc 很容易溶于水（1.1 m 表面活性剂），形成扩展的各向同性胶束溶液相，随后是层状液晶相。与具有一价 Cl- (n ≈ 102)、OH- (n ≈ 37) 和 CH3COO- (n ≈ 42) 抗衡离子的相应系统相比，在具有二价 SO2-4 抗衡离子的表面活性剂系统中形成的单层状相可以在其层片之间结合明显更少量的水（n ≈ 14.4 摩尔水/摩尔表面活性剂离子），而形成所需的最少量的水 (n = 3-5)层状相在系统之间没有显着差异。此外，与在水性系统中获得两个层状相的溴化物（DDAB）系统相比，所有系统仅产生一种层状液晶相。与其他系统不同，DDAS 系统在加热时形成两个各向同性溶液相：一是富含水的 L1 相，表面活性剂含量低于 5 wt%，另一种是 L2 相，表面活性剂含量高于 45 wt%，两相在 353 K 以上共存。层状相的热稳定性按 DDAAc ≈ DDAS < DDAC < DDAOH ≈ DDAB 的顺序增加。二元硫酸盐体系中形成的层状相对于十二烷的溶胀能力非常有限（约3%）。此外，在三元DDAS系统中发现存在三个新的均质相；富油区的立方液晶相（约 49% 油），约 30-38% 的水和约 20-30% 的油之间的六方液晶相，以及约 62-几乎 100% 的水的窄各向同性溶液相，其中只有很少的油百分比。三元DDAS体系的相行为与三元DDAB体系几乎相同，但两个体系中单相在三角形中的位置和某些相的微观结构却截然不同。相行为和相稳定性可以根据静电效应和表面活性剂堆积参数来理解。
The phase equilibria for four binary (temperature vs composition) surfactant systems didodecyldimethylammonium sulphate (DDAS), hydroxide (DDAOH), acetate (DDAAc), and chloride (DDAC) with water and one isothermal ternary system (DDAS-water-dodecane) have been studied by water deuteron NMR and polarizing microscopy methods. Both DDAS and DDAC surfactants are practically insoluble in water (≈3.5 × 10-3 m DDAS and ≈ 1.4 × 10-2 m DDAC) (m, moles of surfactant per kg of water) at 298 K, but they swell in water, each giving rise to a lamellar liquid crystalline phase. On the other hand, DDAOH and DDAAc are easily soluble in water (1.1 m surfactant) forming extended isotropic micellar solution phases which are followed by a lamellar liquid crystalline phase. The single lamellar phase formed in the surfactant system with divalent SO2-4 counterion can incorporate significantly smaller amounts of water (n ≈ 14.4 moles of water per mole surfactant ion) between their lamellae compared to the corresponding system with monovalent Cl- (n ≈ 102), OH- (n ≈ 37), and CH3COO- (n ≈ 42) counterions, whereas the minimum amounts of water (n = 3-5) necessary to form the lamellar phase does not differ significantly among the systems. Moreover, all systems yield only one lamellar liquid crystalline phase compared to the bromide (DDAB) system in which two lamellar phases are obtained in the aqueous system. Unlike other systems, the DDAS system, on heating, forms two isotropic solution phases: one, water-rich L1 phase exists below ≈5 wt% of surfactant and the other, L2 phase, above 45 wt% of surfactant and the two phases coexist above 353 K. Thermal stability of the lamellar phase increases in the order DDAAc ≈ DDAS < DDAC < DDAOH ≈ DDAB. The lamellar phase formed in the binary sulphate system has very limited swelling capability with dodecane (≈3%). In addition, in the ternary DDAS system three new homogeneous phases are found to exist; a cubic liquid crystalline phase in the oil-rich region (≈49% oil), a hexagonal liquid crystalline phase between ≈30-38% of water and ≈20-30% of oil and a narrow isotropic solution phase with few percent of oil and extending between ≈62-almost 100% of water. The phase behavior of the ternary DDAS system is almost identical to that of the ternary DDAB system, but the location of single phases in the triangle and microstructure of some phases are drastically different between the two systems. The phase behavior and phase stability may be understood in terms of electrostatic effects and surfactant packing parameters.