Teng Minmin, Song Aixin, Liu Liping, Hao Jingcheng
Key Laboratory of Colloid and Interface Chemistry, Shandong University, Ministry of Education, Jinan, PR China.
J Phys Chem B. 2008 Feb 14;112(6):1671-5. doi: 10.1021/jp075767t. Epub 2008 Jan 19.
A Ca(2+) -ligand-coordinated vesicle phase was prepared from a mixture of tetradecyldimethylamine oxide (C14DMAO) and calcium tetradecylamidomethyl sulfate [(CH3(CH2)13NHCOCH2OSO3)2Ca] in aqueous solution. At the appropriate mixing ratios, Ca(2+) -ligand coordination results in the formation of molecular bilayers because Ca(2+) can firmly bind to the head groups of C14DMAO and (CH3(CH2)13NHCOCH2OSO3)2Ca by complexation which reduces the area of head group. In this system, no counterions in aqueous solution exist because of the Ca(2+) -ligand coordination, and the bilayer membranes are not shielded by salts, i.e., a salt-free but charged molecular bilayer. The structures of the birefringent solutions of (CH3(CH2)13NHCOCH2OSO3)2Ca and C14DMAO mixtures were determined by transmission electron microscopy (TEM) images and rheological measurements, demonstrating that the birefringent sample solutions consist of vesicles. The Ca(2+) -ligand complex vesicle phase was used as a microreactor to prepare calcium oxalate (CaC2O4) crystals. Dimethyl oxalate, as a precursor, can hydrolyze to oxalic acid and methanol. Oxalic acid should precipitate Ca(2+) ions binding to the head groups of C14DMAO and (CH3(CH2)13NHCOCH2OSO3)2Ca to produce CaC2O4 crystals (Ca(2+) + H2C2O4 --> CaC2O4 (downward arrow) + 2H+). The obtained particles were CaC2O4 monohydrate, which were dominated by (020) faces. CaC2O4 precipitates were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared (FT-IR) analysis. After removal of CaC2O4 precipitates, a new cationic and anionic (catanionic) vesicle phase was constructed through electrostatic interaction between cationic C14DMAOH+ (C14DMAO + H+ --> C14DMAOH+) and anionic CH3(CH12)13 NHCOCH2OSO3-.
通过将十四烷基二甲基氧化胺（C14DMAO）和十四烷基酰胺甲基硫酸钙[（CH3(CH2)13NHCOCH2OSO3）2Ca]在水溶液中混合，制备了一种Ca(2+) -配体配位的囊泡相。在适当的混合比例下，Ca(2+) -配体配位导致分子双层的形成，因为Ca(2+) 可以通过络合作用牢固地结合到C14DMAO和（CH3(CH2)13NHCOCH2OSO3）2Ca的头部基团上，这会减小头部基团的面积。在该体系中，由于Ca(2+) -配体配位，水溶液中不存在抗衡离子，双层膜不会被盐屏蔽，即形成了无盐但带电荷的分子双层。通过透射电子显微镜（TEM）图像和流变学测量确定了（CH3(CH2)13NHCOCH2OSO3）2Ca和C14DMAO混合物的双折射溶液的结构，表明双折射样品溶液由囊泡组成。Ca(2+) -配体复合囊泡相被用作微反应器来制备草酸钙（CaC2O4）晶体。草酸二甲酯作为前体，可以水解为草酸和甲醇。草酸会沉淀与C14DMAO和（CH3(CH2)13NHCOCH2OSO3）2Ca头部基团结合的Ca(2+) 离子，从而生成CaC2O4晶体（Ca(2+) + H2C2O4 --> CaC2O4（向下箭头）+ 2H+）。得到的颗粒是一水合草酸钙，以（020）面为主。通过X射线衍射（XRD）、扫描电子显微镜（SEM）和傅里叶变换红外（FT-IR）分析对草酸钙沉淀进行了表征。去除草酸钙沉淀后，通过阳离子C14DMAOH+（C14DMAO + H+ --> C14DMAOH+）和阴离子CH3(CH12)13 NHCOCH2OSO3-之间的静电相互作用构建了一种新的阳离子和阴离子（阴阳离子）囊泡相。
