Highly Stable Layered Double Hydroxide Colloids: A Direct Aqueous Synthesis Route from Hybrid Polyion Complex Micelles

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• 作者：G茅raldine Layrac ; Mathias Destarac ; Corine G茅rardin ; Didier Tichit
• 刊名：Langmuir
• 出版年：2014
• 出版时间：August 19, 2014
• 年：2014
• 卷：30
• 期：32
• 页码：9663-9671
• 全文大小：373K
• ISSN：1520-5827

文摘

Aqueous suspensions of highly stable Mg/Al layered double hydroxide (LDH) nanoparticles were obtained via a direct and fully colloidal route using asymmetric poly(acrylic acid)-b-poly(acrylamide) (PAA-b-PAM) double hydrophilic block copolymers (DHBCs) as growth and stabilizing agents. We showed that hybrid polyion complex (HPIC) micelles constituted of almost only Al³⁺ were first formed when mixing solutions of Mg²⁺ and Al³⁺ cations and PAA₃₀₀₀-b-PAM₁₀₀₀₀ due to the preferential complexation of the trivalent cations. Then mineralization performed by progressive hydroxylation with NaOH transformed the simple DHBC/Al³⁺ HPIC micelles into DHBC/aluminum hydroxide colloids, in which Mg²⁺ ions were progressively introduced upon further hydroxylation leading to the Mg鈥揂l LDH phase. The whole process of LDH formation occurred then within the confined environment of the aqueous complex colloids. The hydrodynamic diameter of the DHBC/LDH colloids could be controlled: it decreased from 530 nm down to 60 nm when the metal complexing ratio R (R = AA/(Mg + Al)) increased from 0.27 to 1. This was accompanied by a decrease of the average size of individual LDH particles as R increased (for example from 35 nm at R = 0.27 down to 17 nm at R = 0.33), together with a progressive favored intercalation of polyacrylate rather than chloride ions in the interlayer space of the LDH phase. The DHBC/LDH colloids have interesting properties for biomedical applications, that is, high colloidal stability as a function of time, stability in phosphate buffered saline solution, as well as the required size distribution for sterilization by filtration. Therefore, they could be used as colloidal drug delivery systems, especially for hydrosoluble negatively charged drugs.