Nanoparticles with a Bicontinuous Cubic Internal Structure Formed by Cationic and Non-ionic Surfactants and an Anionic Polyelectrolyte

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• 作者：John Janiak ; Solmaz Bayati ; Luciano Galantini ; Nicolae V. Pavel ; Karin Schill茅n
• 刊名：Langmuir
• 出版年：2012
• 出版时间：December 4, 2012
• 年：2012
• 卷：28
• 期：48
• 页码：16536-16546
• 全文大小：464K
• 年卷期：v.28,no.48(December 4, 2012)
• ISSN：1520-5827

文摘

Nanoparticles with an internal structure have been prepared by dispersing under dilute conditions poly(acrylic acid) with a polymerization degree n = 6000 (PAA₆₀₀₀) together with a cationic surfactant hexadecyltrimethylammonium hydroxide (C₁₆TAOH) and the non-ionic surfactant penta(ethylene glycol) monododecyl ether (C₁₂E₅) in water. The nanoparticles are formed at different mixing ratios in the corresponding two-phase regions (liquid crystalline phase/dilute isotropic phase) of the C₁₆TAPA₆₀₀₀ complex salt/C₁₂E₅/water ternary phase diagram. The particles consist of polyacrylate PA₆₀₀₀^{鈥?/sup> polyions, C₁₆TA+ surfactant ions, and C₁₂E₅. Their internal ordering was identified by small-angle X-ray scattering (SAXS) to be either bicontinuous cubic with the Ia3d crystallographic space group or normal hexagonal depending upon the amount of C₁₂E₅. The bicontinuous cubic phase, to our knowledge never observed before in polyelectrolyte鈥搒urfactant particle systems, was inferred by SAXS experiments. The data also showed that this structure is thermoresponsive in a reversible manner. The bicontinuous cubic space group transforms from Ia3d to Im3m as the temperature decreases from 25 to 15 掳C. According to dynamic light scattering and electrophoretic mobility measurements, the particles have a well-defined size (apparent hydrodynamic radii R_H in the range of 88鈥?40 nm) and carry a positive net charge. The size of the nanoparticles is stable up to 1 month. The faceted nanoparticles are visualized by cryogenic transmission electron microscopy that also reveals their coexistence with thread-like C₁₂E₅ micelles.}