Synthesis of Hollow CaCO3 Nanospheres Templated by Micelles of Poly(styrene-b-acrylic acid-b-ethylene glycol) in Aqueous Solutions

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• 作者：Bishnu Prasad Bastakoti ; Sudhina Guragain ; Yuuichi Yokoyama ; Shin-ichi Yusa ; Kenichi Nakashima
• 刊名：Langmuir
• 出版年：2011
• 出版时间：January 4, 2011
• 年：2011
• 卷：27
• 期：1
• 页码：379-384
• 全文大小：852K
• 年卷期：v.27,no.1(January 4, 2011)
• ISSN：1520-5827

文摘

An asymmetric triblock copolymer, poly(styrene-b-acrylic acid-b-ethylene glycol) (PS-b-PAA-b-PEG), was synthesized via reversible addition鈭抐ragmentation chain transfer controlled radical polymerization. Micelles of PS-b-PAA-b-PEG with PS core, PAA shell, and PEG corona were then prepared in aqueous solutions, followed by extensive characterization based on dynamic light scattering, zeta-potential, and transmission electron microscopy (TEM) measurements. The well-characterized micelles were used to fabricate hollow nanospheres of CaCO<sub>3sub> as a template. It was elucidated from TEM measurements that the hollow nanospheres have a uniform size with cavity diameters of ca. 20 nm. The X-ray diffraction analysis revealed a high purity and crystallinity of the hollow nanospheres. The hollow CaCO<sub>3sub> nanospheres thus obtained have been used for the controlled release of an anti-inflammatory drug, naproxen. The significance of this study is that we have overcome a previous difficulty in the synthesis of hollow CaCO<sub>3sub> nanospheres. After mixing of Ca<sup>2+sup> and CO<sub>3sub><sup>2鈭?/sup> ions, the growth of CaCO<sub>3sub> is generally quite rapid to induce large crystal, which prevented us from obtaining hollow CaCO<sub>3sub> nanospheres with controlled structure. However, we could solve this issue by using micelles of PS-b-PAA-b-PEG as a template. The PS core acts as a template that can be removed to form a cavity of hollow CaCO<sub>3sub> nanospheres, the PAA shell is beneficial for arresting Ca<sup>2+sup> ions to produce CaCO<sub>3sub>, and the PEG corona stabilizes the CaCO<sub>3sub>/micelle nanocomposite to prevent secondary aggregate formation.