Li Xin, Dong Shuli, Jia Xiangfeng, Song Aixin, Hao Jingcheng
Key Laboratory of Colloid and Interface Chemistry, Shandong University, Ministry of Education, Jinan 250100, China.
Chemistry. 2007;13(34):9495-502. doi: 10.1002/chem.200700778.
Weakly basic tetradecyldimethylaminoxide (C14DMAO) molecules can be protonated to form a cationic surfactant, C14DMAOH+, by an acidic fluorocarbon surfactant, an 8-2-fluorotelomer unsaturated acid (C7F15CF==CHCOOH), to form a salt-free cationic and anionic (cat-anionic) fluoro/hydrocarbon surfactant system in aqueous solution. The high Krafft point of C7F15CF==CHCOOH was largely reduced as a result of being mixed with a C14DMAO micelle solution. A study of the phase behavior of the new salt-free cat-anionic fluoro/hydrocarbon surfactant system clearly indicates the existence of a birefringent Lalpha-phase region at (25.0+/-0.1) degrees C. The birefringent Lalpha phase consists of vesicles, which include uni- and multilamellar vesicles with one to dozens of shells, and oligovesicular vesicles, as demonstrated by freeze-fracture and cryo-transmission electron microscopy (FF- and cryo-TEM) images. The size distribution and structural transitions in the salt-free cat-anionic fluoro/hydrocarbon surfactant system were studied by dynamic light scattering (DLS) and 1H and 19F NMR spectroscopy. The formation of a salt-free cat-anionic vesicle phase could be induced by the strong electrostatic interaction between the cationic hydrocarbon C14DMAOH+ and the anionic fluorocarbon C7F15CF==CHCOO-, which provided evidence that the electrostatic interaction between the cationic and anionic surfactants is larger than the nonsynergistic interaction between the stiff fluorocarbon and the soft hydrocarbon chains of the surfactants.
弱碱性十四烷基二甲基氧化胺（C14DMAO）分子可被酸性氟碳表面活性剂8-2-氟调聚物不饱和酸（C7F15CF==CHCOOH）质子化，形成阳离子表面活性剂C14DMAOH+，从而在水溶液中形成无盐阳离子和阴离子（阳离子-阴离子）氟/烃表面活性剂体系。由于与C14DMAO胶束溶液混合，C7F15CF==CHCOOH的高克拉夫特点大幅降低。对新型无盐阳离子-阴离子氟/烃表面活性剂体系相行为的研究清楚地表明，在（25.0±0.1）℃存在双折射Lα相区。通过冷冻断裂和低温透射电子显微镜（FF-和低温-TEM）图像证明，双折射Lα相由囊泡组成，包括具有一到几十个壳层的单室和多室囊泡以及寡囊泡。通过动态光散射（DLS）以及1H和19F核磁共振光谱研究了无盐阳离子-阴离子氟/烃表面活性剂体系的尺寸分布和结构转变。阳离子烃C14DMAOH+与阴离子氟碳C7F15CF==CHCOO-之间的强静电相互作用可诱导形成无盐阳离子-阴离子囊泡相，这证明阳离子和阴离子表面活性剂之间的静电相互作用大于表面活性剂中刚性氟碳链和柔性烃链之间的非协同相互作用。
