Effects of length and hydrophilicity/hydrophobicity of diamines on self-assembly of diamine/SDS gemini-like surfactants
Effects of length and hydrophilicity/hydrophobicity of diamines on self-assembly of diamine/SDS gemini-like surfactants
复制标题
二胺长度和亲水/疏水性对二胺/SDS Gemini-like表面活性剂自组装的影响
DOI：
10.1039/c7sm02058a
复制
发表时间：
2017-12-21
期刊：
影响因子：
3.4
通讯作者：
Wang, Yilin
中科院分区：
文献类型：
--
作者：
Chen, Zhidi;Penfold, Jeffrey;Wang, Yilin
这项工作利用表面张力、小角中子散射、等温滴定微量热法和低温透射电子显微镜研究了由阴离子表面活性剂十二烷基硫酸钠（SDS）和带有不同长度的亲水或疏水间隔基的阳离子带电波拉型二胺形成的双子表面活性剂。所有二胺/SDS 混合物的临界胶束浓度 (CMC) 和 CMC 表面张力 (gCMC) 均明显低于 SDS。无论二胺的亲水性/疏水性如何，较短的二胺都会更大程度地降低 gCMC。同时，无论是具有较长间隔基的疏水性二胺还是具有较短间隔基的亲水性二胺更有利于降低CMC，并导致球形胶束向棒状或蠕虫状胶束转变。这主要是由于SDS与二胺之间的静电结合形成了双子表面活性剂，其中由于带相反电荷的二胺与SDS的静电结合，SDS相邻头基之间的静电排斥力变得更弱，并且较长的疏水间隔基也可能弯曲到胶束的疏水域中以促进胶束生长。然而，亲水间隔基与头基区域更相容，导致胶束具有更大的曲率。这项工作有助于理解构建的Gemini-like表面活性剂的性质与连接分子的性质之间的关系，并为有效提高表面活性剂的性能提供指导。
This work studied gemini-like surfactants formed from anionic surfactant sodium dodecyl sulfate (SDS) and cationic charged bola-type diamines with hydrophilic or hydrophobic spacers of different lengths using surface tension, small angle neutron scattering, isothermal titration microcalorimetry and cryogenic transmission electron microscopy. The critical micelle concentrations (CMC) and the surface tension at CMC (gCMC) for all the diamine/SDS mixtures are markedly lower than that of SDS. The shorter diamines reduce gCMC to a greater extent regardless of the hydrophilicity/hydrophobicity of the diamines. Meanwhile, either the hydrophobic diamine with a longer spacer or the hydrophilic diamine with a shorter spacer is more beneficial to decrease CMC and leads to the transition from spherical micelles into rodlike or wormlike micelles. This is principally because of the formation of gemini-like surfactants by the electrostatic binding between SDS and the diamines, where the electrostatic repulsion between the adjacent headgroups of SDS becomes much weaker due to the electrostatic binding of oppositely charged diamine with SDS, and the longer hydrophobic spacer may also bend into the hydrophobic domain of micelles to promote micellar growth. However, the hydrophilic spacers are more compatible with the headgroup region, leading to micelles with a larger curvature. This work contributes to the understanding of the relationship between the properties of constructed gemini-like surfactants and the natures of connecting molecules, and provides guidance to efficiently improve the performance of surfactants.