Department of Industrial Chemistry, Faculty of Engineering, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku, Tokyo 162-8601, Japan.
Department of Industrial Chemistry, Faculty of Engineering, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku, Tokyo 162-8601, Japan.
J Colloid Interface Sci. 2021 Apr 15;588:418-426. doi: 10.1016/j.jcis.2020.12.103. Epub 2020 Dec 31.
Novel photoresponsive hybrid surfactants, in which a combination of perfluoroalkyl and alkyl chains and cationic head groups are connected via azobenzene moieties, are excellent candidates for assembling low-molecular-weight organogels (LMOGs) with reversibly switchable viscoelasticities triggered by external stimuli.
The structure-composition-property relationships of gels assembled with the hybrid surfactants were investigated by UV-vis and NMR spectroscopy, SEM, XRD, and rheology.
Hybrid surfactants containing perfluorohexyl chains with more than six carbons gelled in a variety of organic solvents at concentrations of less than a few percent. In particular, compositions with the perfluorooctyl and somewhat shorter hydrocarbon chains (C1-C4) gelled in both organic solvents and water. The gellable solvent species can be well grouped according to their solubility parameters, suggesting that gelation properties can be predicted from the chemical structure of the surfactant. Mechanical and structural investigations revealed that gel viscoelasticity can be reversibly altered by applying photo, shear, and heat stimuli, which is achieved through the formation and deformation of lamella-like molecular aggregates. The multi-responsive gelation and facile molecular design of the present hybrid surfactants will expand the fields in which fluorinated LMOGs can be applied.
新型光响应混合表面活性剂，其中通过偶氮苯部分连接全氟烷基和烷基链以及阳离子头基的组合，是通过外部刺激可组装具有可反复切换的粘弹性的低分子量有机凝胶（LMOG）的绝佳候选物。
通过 UV-vis 和 NMR 光谱、SEM、XRD 和流变学研究了用混合表面活性剂组装的凝胶的结构-组成-性质关系。
含有超过六个碳原子的全氟己基链的混合表面活性剂在浓度低于百分之几的多种有机溶剂中形成凝胶。特别是，具有全氟辛基和稍短的碳氢链（C1-C4）的组成在有机溶剂和水中都形成凝胶。根据它们的溶解度参数，可将可凝胶化的溶剂种类很好地分组，表明可以从表面活性剂的化学结构预测凝胶化性质。力学和结构研究表明，通过施加光、剪切和热刺激，可以可逆地改变凝胶的粘弹性，这是通过层状分子聚集体的形成和变形来实现的。本混合表面活性剂的多响应凝胶化和易于分子设计将扩大可应用氟化物 LMOG 的领域。
