Fabrication of Two Types of Shell-Cross-Linked Micelles with “Inverted” Structures in Aqueous Solution from Schizophrenic Water-Soluble ABC Triblock Copolymer via Click Chemistry

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• 作者：Xiaoze Jiang ; Guoying Zhang ; Ravin Narain ; Shiyong Liu
• 刊名：Langmuir
• 出版年：2009
• 出版时间：February 17, 2009
• 年：2009
• 卷：25
• 期：4
• 页码：2046-2054
• 全文大小：241K
• 年卷期：v.25,no.4(February 17, 2009)
• ISSN：1520-5827

文摘

A well-defined ABC triblock copolymer, poly(2-(2-methoxyethoxy)ethyl methacrylate)-b-poly(2-(dimethylamino)ethyl methacrylate)-b-poly(2-(diethylamino)ethyl methacrylate) (PMEO₂MA-b-PDMA-b-PDEA), was synthesized via sequential atom transfer radical polymerization using ethyl 2-bromoisobutyrate as the initiator. Reacting the triblock precursor with propargyl bromide in anhydrous tetrahydrofuran yielded PMEO₂MA-b-P(DMA-co-QDMA)-b-PDEA triblock copolymer with “clickable” moieties, where QDMA was quaternized DMA residues. PMEO₂MA-b-P(DMA-co-QDMA)-b-PDEA triblock copolymer exhibited “schizophrenic” micellization behavior in aqueous solution, forming three-layer onion-like PMEO₂MA-core and PDEA-core micelles upon proper adjustment of the solution pH and temperature. For temperature-induced formation of PMEO₂MA-core micelles at acidic pH, the critical micellization temperature can be tuned by incorporating oligo(ethylene glycol) methyl ether methacrylate (OEGMA; the mean degree of polymerization was 8−9) residues into the PMEO₂MA block, shifting from 38 to 43 °C as the OEGMA contents varied in the range of 0−10 mol %. In both types of micelles, the inner shell layer consisted of the middle P(DMA-co-QDMA) segment. Subsequently, cross-linking with tetra(ethylene glycol) diazide via click chemistry in the presence of copper catalysts led to the facile preparation of two types of shell-cross-linked (SCL) micelles with “inverted” structures in purely aqueous solution. The cores and coronas of SCL micelles exhibited multiresponsive swelling/shrinking and collapse/aggregation behavior, respectively. To the best of our knowledge, this represents the first report of the fabrication of two types of SCL micelles with inverted structures from a single schizophrenic water-soluble triblock copolymer in purely aqueous solution.