Fabozzi Antonio, Russo Krauss Irene, Vitiello Rosa, Fornasier Marco, Sicignano Luca, King Stephen, Guido Stefano, Jones Christopher, Paduano Luigi, Murgia Sergio, D'Errico Gerardino
Department of Chemical Sciences, University of Naples Federico II, Via Cintia 4, Complesso Universitario di Monte Sant'Angelo, I-80126 Naples, Italy.
Department of Chemical Sciences, University of Naples Federico II, Via Cintia 4, Complesso Universitario di Monte Sant'Angelo, I-80126 Naples, Italy; CSGI, Consorzio Interuniversitario per lo Sviluppo dei Sistemi a Grande Interfase, Via della Lastruccia 3, I-50019 Sesto Fiorentino, Florence, Italy.
J Colloid Interface Sci. 2019 Sep 15;552:448-463. doi: 10.1016/j.jcis.2019.05.052. Epub 2019 May 18.
The rational design of branched-tail surfactants is a suitable strategy to obtain low-viscosity surfactant-rich isotropic aqueous mixtures with negligible effects on biodegradability. This opens a way to the design of concentrated ("water-free") surfactant formulations, highly attractive for their ecological and economic benefits.
The aggregation behaviour of N,N-dimethyl-2-propylheptan-1-amine oxide (CDAO-branched) in aqueous mixtures is investigated across the entire composition range by polarized optical microscopy, small angle X-ray and neutron scattering, electron paramagnetic resonance, and pulse-gradient stimulated echo nuclear magnetic resonance. The humidity scanning quartz crystal microbalance with dissipation monitoring technique is validated as a tool for the fast screening of surfactants phase behaviour. Furthermore, the shear viscosities and viscoelastic moduli of the systems are determined by rheological measurements.
With respect to the linear isomer, CDAO-branched presents a much lower tendency to form lyotropic liquid crystalline phases. Except for a narrow composition and temperature range in which a lamellar structure is observed, CDAO-branched aqueous mixtures are isotropic liquids whose microstructure changes, with increasing concentration, from micellar solutions to unstructured dispersions of hydrated surfactant molecules. Low-viscosity was found for all these mixtures, including the most concentrated ones. Thus, the introduction of a single short side-chain in the tail is demonstrated to be an effective approach to increase the active concentration in surfactant formulations.
合理设计支链尾表面活性剂是获得低粘度、富含表面活性剂的各向同性水性混合物的合适策略，且对生物降解性影响可忽略不计。这为设计浓缩（“无水”）表面活性剂配方开辟了一条途径，因其生态和经济效益而极具吸引力。
通过偏光显微镜、小角X射线和中子散射、电子顺磁共振以及脉冲梯度激发回波核磁共振，在整个组成范围内研究了N,N-二甲基-2-丙基庚烷-1-胺氧化物（CDAO-支链）在水性混合物中的聚集行为。验证了带有耗散监测技术的湿度扫描石英晶体微天平作为快速筛选表面活性剂相行为的工具。此外，通过流变学测量确定了体系的剪切粘度和粘弹性模量。
相对于线性异构体，CDAO-支链形成溶致液晶相的倾向要低得多。除了在一个狭窄的组成和温度范围内观察到层状结构外，CDAO-支链水性混合物是各向同性液体，其微观结构随着浓度的增加从胶束溶液变为水合表面活性剂分子的无结构分散体。所有这些混合物，包括最浓缩的混合物，都具有低粘度。因此，在尾部引入单个短侧链被证明是提高表面活性剂配方中活性浓度的有效方法。
