Dispersible Shaped Nanoobjects from Bulk Microphase Separation of High Tg Block Copolymers without Chemical Cross-linking

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• 作者：Jianglei Qin ; Yongming Chen ; Dadong Yan ; Fu Xi
• 刊名：Macromolecules
• 出版年：2010
• 出版时间：December 28, 2010
• 年：2010
• 卷：43
• 期：24
• 页码：10652-10658
• 全文大小：876K
• 年卷期：v.43,no.24(December 28, 2010)
• ISSN：1520-5835

文摘

This work presents a facile procedure to fabricate the nanoobjects of block copolymers with lamellar, cylindrical, and spherical morphology via bulk microphase separation and dispersing in selective solvents without chemical cross-linking. The morphologies of these nanoobjects in solution were stabilized by their cores in a glassy state. First the bulk microphase separation of a series of poly(tert-butyl acrylate)-block-polystyrene (PtBA-b-PS) block copolymers was conducted to generate the ordered materials with lamellar, cylindrical and spherical morphology with the PS domains as the discontinuous phases as characterized by small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). Then by direct dispersing these microphase separated materials into methanol that is a selective solvent of the PtBA segments, the nanoobjects, lamellae, cylinders and spheres, inherited from their bulk structures were obtained. As a contrast, micellization of these block copolymers directly in methanol all gave spherical micelles. Therefore, those nanoobjects of PtBA-b-PS via bulk microphase separation were thermodynamic unfavorable in methanol but were fixed by the glassy PS cores. Under a refluxing condition of methanol, the nanoobjects of lamellae and cylinders were transformed into spherical micelles of thermodynamic stucture as traced by TEM. It was observed that the dispersed lamellae transformed first into nanorods and then into spheres during refluxing, whereas the cylinders gradually became spheres. Furthermore, the PtBA segments tethered onto the glassy PS cores were hydrolyzed into the poly(acrylic acid) (PAA) segments by treating with trifluoroacetic acid, and as a result, the PAA coated nanoobjects of different morphology dispersed in the basic water were obtained without chemical cross-linking.