Siddiqui Umme Salma, Ghosh Goutam
Department of Chemistry, Aligarh Muslim University, Aligarh 202 002, India.
Langmuir. 2006 Nov 21;22(24):9874-8. doi: 10.1021/la061694d.
Dynamic light scattering (DLS) measurements have been performed at 30 degrees C to see the effects of additives on the microstructure of gemini alkanediyl-alpha,omega-bis(dimethylcetylammonium bromide) surfactants, (Br-, n-C16H33N+Me2-(CH2)s-Me2- N+n-C16H33, Br-, 16-s-16, where s = 4, 5, 6). In pure aqueous solutions, the hydrodynamic diameter, Dh, was found to increase rapidly with geminis in comparison to their monomeric counterpart cetyltrimethylammonium bromide (n-C16H33N+Me3, Br-, CTAB) on increasing surfactant concentration. The additives considered in the present study are n-alcohols (C4-C6OH) and n-hexylamine (C6NH2) on the micellar growth of 0.03 M 16-4-16 in the presence and absence of 0.001 M KBr. The presence of 0.001 M KBr or organic additives at lower concentrations singly or jointly has little effect on the micellar size. As the chain length of the additive increases, the size increases with the increase of additive concentration, the magnitude being substantial in the presence of 0.001 M KBr. However, for equal chain length additives (C6OH, C6NH2), the effect was greater for C6OH. In case of C6NH2, the value of Dh reaches to almost constancy when the concentration of the additive was increased. Increased effectiveness of additives in the presence of added salt (KBr) is discussed in light of electrostatic and hydrophobic forces operating in the solution, which are always responsible for growth processes.
已在30摄氏度下进行动态光散射（DLS）测量，以观察添加剂对双子型链烷二基-α,ω-双（二甲基十六烷基溴化铵）表面活性剂（Br⁻，n-C₁₆H₃₃N⁺Me₂-(CH₂)ₛ-Me₂-N⁺n-C₁₆H₃₃，Br⁻，16-s-16，其中s = 4、5、6）微观结构的影响。在纯水溶液中，与单体十六烷基三甲基溴化铵（n-C₁₆H₃₃N⁺Me₃，Br⁻，CTAB）相比，发现随着表面活性剂浓度的增加，双子型表面活性剂的流体动力学直径Dh迅速增大。本研究中考虑的添加剂是正醇（C₄-C₆OH）和正己胺（C₆NH₂），它们在有和没有0.001 M KBr的情况下对0.03 M 16-4-16的胶束生长的影响。单独或联合存在较低浓度的0.001 M KBr或有机添加剂对胶束大小影响很小。随着添加剂链长的增加，胶束大小随添加剂浓度的增加而增大，在存在0.001 M KBr的情况下增幅较大。然而，对于链长相等的添加剂（C₆OH，C₆NH₂），C₆OH的影响更大。在C₆NH₂的情况下，当添加剂浓度增加时，Dh的值几乎达到恒定。根据溶液中起作用的静电力和疏水力对添加盐（KBr）存在下添加剂有效性的增加进行了讨论，这些力总是对生长过程起作用。
