Abnormal micellar growth in sugar-based and ethoxylated nonionic surfactants and their mixtures in dilute regimes using analytical ultracentrifugation.
Abnormal micellar growth in sugar-based and ethoxylated nonionic surfactants and their mixtures in dilute regimes using analytical ultracentrifugation.
复制标题
使用分析超速离心在稀释状态下观察糖基和乙氧基化非离子表面活性剂及其混合物的异常胶束生长。
作者：
Rui Zhang;P. Somasundaran
为了建立控制其在混合体系中的吸附、增溶和胶束行为的表面活性剂的结构-性质关系，并建立基于这种关系的预测模型，有必要获得这些复杂体系中存在的各种物种的定量信息。分析超离心技术首次被用于表征混合胶束溶液中存在的物种，因为它具有根据颗粒的大小和形状分离颗粒的强大能力。研究了两种非离子表面活性剂n-十二烷基- β -d -麦芽糖苷（DM）和壬基酚乙氧基癸基醚（NP-10）及其1:1摩尔比的混合物。在临界胶束浓度（cmc）下，非离子表面活性剂及其混合物的胶束形状不对称。有趣的是，与离子表面活性剂不同，非离子表面活性剂的胶束生长被发现发生在浓度直接高于cmc的情况下。沉降速度和沉降平衡实验结果表明，壬基酚乙氧基化癸基醚溶液及其与正十二烷基-d -麦芽糖苷的混合物中存在两种胶束，而正十二烷基-d -麦芽糖苷溶液中只有一种胶束存在。1型胶束是cmc处的初级胶束，2型胶束是拉长胶束。n-十二烷基- -d -麦芽糖苷和壬基酚聚氧基癸基醚胶束形状的差异是由其分子结构检测到的填料参数决定的。
To develop structure-property relationships for surfactants that control their adsorption, solubilization, and micellization behavior in mixed systems and to develop predictive models based on such relationships, it is necessary to acquire quantitative information on various species present in these complex systems. The analytical ultracentrifugation technique is selected for the first time to characterize the species present in mixed micellar solutions due to its powerful ability to separate particles on the basis of their size and shape. Two nonionic surfactants, n-dodecyl-beta-D-maltoside (DM) and nonyl phenol ethoxylated decyl ether (NP-10), and their 1:1 molar ratio mixture were investigated in this study. Micelles of the nonionic surfactants and their mixture are asymmetrical in shape at the critical micelle concentration (cmc). Interestingly, unlike ionic surfactants, the micellar growths of the nonionic surfactants were found to occur at concentrations immediately above the cmc. The results from both sedimentation velocity and sedimentation equilibrium experiments suggest coexistence of two types of micelles in nonyl phenol ethoxylated decyl ether solutions and in its mixture with n-dodecyl-beta-D-maltoside, while only one micellar species is present in n-dodecyl-beta-D-maltoside solutions. Type 1 micelles were primary micelles at the cmc, while type 2 micelles were elongated micelles. The differences in the micellar shapes of n-dodecyl-beta-D-maltoside and nonyl phenol ethoxylated decyl ether are attributed to packing parameters detected by their molecular structures.