文献类型：期刊文献

英文题名：Monolayer effect of a gemini surfactant with a rigid biphenyl spacer on its self-crystallization at the air/liquid interface

作者：Chen, Qibin;Yao, Junyao;Hu, Xin;Shen, Jincheng;Sheng, Yujie;Liu, Honglai[1]

机构：[1]E China Univ Sci & Technol, Key Lab Adv Mat, Shanghai 200237, Peoples R China; E China Univ Sci & Technol, Dept Chem, Shanghai 200237, Peoples R China

年份：2015

卷号：48

起止页码：728

外文期刊名：JOURNAL OF APPLIED CRYSTALLOGRAPHY

收录：;EI(收录号：20152300925996);WOS:【SCI-EXPANDED(收录号:WOS:000355562000013)】；

基金：This work is supported by the National Natural Science Foundation of China (No. 21273074) and the Fundamental Research Funds for the Central Universities of China (WK1213003).

语种：英文

外文关键词：gemini surfactants; crystallization; self-assembly; interfaces

摘要：A gemini surfactant with a biphenyl spacer can spontaneously generate crystals at the air/solution interface. X-ray crystallography reveals that surfactant molecules exhibit an almost fully extended conformation with interdigitating alkyl chains, together with an approximate co-planarity of two C-C-C planes in two alkyl chains of one gemini molecule, and a prominent dihedral angle between the benzene rings and C-C-C planes of the alkyl chains. Infrared reflection-absorption spectroscopy shows that the gemini surfactant was stretched at the air/water interface, with the hydrocarbon chains oriented at a tilt angle of similar to 75 degrees with respect to the surface normal. In particular, the biphenyl group is more or less perpendicular to the water surface, and the C-C-C plane of the alkyl chain tends to be parallel to the water surface. Both results point out a remarkable similarity in the molecular conformation between the crystal and the monolayer. Meanwhile, dynamic light scattering and transmission electron microscopy results indicate that the crystallization of such gemini surfactants at the interface is contrary to the crystallization behavior in the bulk phase, meaning that the surfactant solution can only form a supersaturated solution as it is cooled, though the crystallization temperature of 296 K is lower than the Krafft temperature (similar to 303 K). Therefore, our findings indicate that the Gibbs monolayer of the gemini surfactant plays a critical role in its interfacial crystallization. Additionally, multiple weak intermolecular interactions, involving van der Waals interaction, pi-pi stacking and cationic-pi interactions, as well as the hydrophobic effect during the aggregation of the gemini molecule in solution, are responsible for the formation of the interfacial crystal.