Structure Transition from Hexagonal Mesostructured Rodlike Silica to Multilamellar Vesicles

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• 作者：Pei Yuan ; Sui Yang ; Hongning Wang ; Meihua Yu ; Xufeng Zhou ; Gaoqing Lu ; Jin Zou ; Chengzhong Yu
• 刊名：Langmuir
• 出版年：2008
• 出版时间：May 6, 2008
• 年：2008
• 卷：24
• 期：9
• 页码：5038 - 5043
• 全文大小：316K
• 年卷期：v.24,no.9(May 6, 2008)
• ISSN：1520-5827

文摘

We studied the synthesis of siliceous structures by using a nonionic block copolymer (Pluronic P123) andperfluorooctanoic acid (PFOA) as cotemplates in an acid-catalyzed sol-gel process. Different siliceous structures wereobtained through systematically varying the molar ratio (R) of PFOA/P123, and the resultant materials were characterizedby X-ray diffraction, scanning electron microscopy, transmission electron microscopy, nitrogen sorption analysis, andFourier-transform infrared spectroscopy. The results are consistent and reveal a structure transition from a highlyordered 2D hexagonal (HEX) mesostructure with a rodlike morphology to multilamellar vesicles (MLVs) with sharpedges when R is increased. The fact that the MLVs are initiated from the end of hexagonally mesostructured rodsprovides key evidence in such a novel structure transition. Our finding indicates that, at least in our observations, theMLVs are developed gradually from HEX structures, rather than by a direct cooperative self-assembly mechanism.It is suggested that PFOA molecules with rigid fluorocarbon chains closely interact with PEO. This interaction modelmay well explain (1) the "wall-thicken" effect in HEX mesostructures by enlarging the hydrophilic PEO moiety (R= 0-1.4), (2) the subsequent HEX to multilamellar structure transition by modifying the hydrophilic/hydrophobicvolume ratio (R = 1.4-2.8), and (3) the formation of MLVs with sharp edges by increasing the bending energy. Thismodel provides insight into the fabrication of novel porous materials by the use of block copolymers and fluorinatedsurfactant mixed templates.