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ABSTRACT: Core-shell-corona (CSC) micelles of asymmetric triblock copolymer, poly(styrene-b-2-vinylpyridine-b-ethylene oxide) (PS-PVP-PEO), containing polystyrene homopolymer (homo-PS) in the core were successfully prepared in aqueous media. The influence of homo-PS contents over the formation of the micelles was investigated thoroughly by various techniques such as dynamic light scattering (DLS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and fluorescence spectroscopy. It was found that the size of the PS core of the micelle was increased by the addition of homo-PS as observed by DLS and TEM techniques. The SEM and TEM measurements confirm the spherical morphology of the micelles and enlargement of PS core over the addition of homo-PS. The increase in the PS core volume of the PS-PVP-PEO micelles is attributed to the insertion of homo-PS in the PS core. The micelles have also been demonstrated as facile soft templates for synthesis of hollow silica nanospheres. The average diameter of the spherical hollow particles could be tuned between 30.6 and 38.8 nm with cavity sizes ranging from 20.7 to 28.5 nm using tetramethoxysilane as silica precursors under mild acidic conditions. The facile synthesis of hollow silica using the CSC micelles with different homo-PS contents indicates that the hollow void size can be controlled within a range of several nanometers.
Journal of Colloid and Interface Science 06/2011; 358(2):354-9. · 3.07 Impact Factor
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Journal of Polymer Science Part A Polymer Chemistry 04/2011; 49(13):2761 - 2770. · 3.92 Impact Factor
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ABSTRACT: Hollow silica nanospheres with uniform size of about 30 nm have been successfully synthesized using a template of ABC triblock copolymer micelles of poly(styrene-b-2-vinyl pyridine-b-ethylene oxide) (PS–PVP–PEO) with a core–shell–corona architecture. In this type of triblock copolymers, the PS block (core) works as a template of the void space of hollow silica, the PVP block (shell) acts as a reaction field for the sol–gel reaction of tetramethoxysilane (TMOS), and the PEO block (corona) stabilizes the polymer/silica composite particles. Use of polymers with different chain lengths of PS, PVP, and PEO led to hollow silica with tunable cavity size and wall thickness. The obtained hollow particles were thoroughly characterized by X-ray diffraction (XRD), thermal (TG/DTA) and nitrogen sorption analyses, infra-red (FT IR) and nuclear magnetic resonance (29Si MAS NMR) spectroscopies, and transmission electron microscopy (TEM). The efficiency of hollow silica nanospheres for lithium-ion rechargeable batteries is demonstrated for the first time. The hollow silica nanoparticles exhibited high cycle performance of up to 500 cycles in the lithium rechargeable batteries through the alloying/dealloying process. The tiny grain size of hollow nanospheres results in less volume expansion and/or contraction during charge/discharge cycles.
Journal of material chemistry. 01/2011; 21:13881.
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Journal of Materials Chemistry 01/2011; 21:13888. · 5.97 Impact Factor
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ABSTRACT: Organic compounds are used as templates to regulate the morphology of inorganic nanostructures. In the present study, we used intermediate filaments (IFs), the major cytoskeleton component of most eukaryotic cells, as a template for hollow silica nanotube preparation. Sol-gel polymerization of tetraethoxysilane proceeded preferentially on the surface of IFs assembled from vimentin protein in vitro, resulting in silica-coated fibres. After removing IFs by calcination, electron microscopy revealed hollow silica nanotubes several micrometers long, with outer diameters of 35-55 nm and an average inner diameter of 10 nm (comparable to that of IFs). Furthermore, the silica nanotubes exhibited a gnarled surface structure with an 18-26 nm repeating pattern (comparable to the 21-nm beading pattern along IFs). Thus, the characteristic morphology of IFs were well replicated into hollow silica nanotubes, suggesting that IFs maybe useful as an organic template.
Journal of biochemistry 09/2009; 146(5):627-31. · 1.95 Impact Factor
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ABSTRACT: Poly(styrene-b-2-vinyl-1-methylpyridinium iodide-b-ethylene oxide) (PS-PVMP-PEO) was synthesized by quaternizing poly(2-vinyl pyridine) block of poly(styrene-b-2-vinyl pyridine-b-ethylene oxide) with iodomethane. Then, PS-PVMP-PEO/ tungstate hybrid micelles were prepared by binding tungstate to the PVMP block at neutral pH in aqueous solutions. The hybrid micelles were characterized by various techniques like dynamic light scattering, scanning electron microscopy, transmission electron microscopy, and zeta-potential measurements. It was found that the PS-PVMP-PEO/tungstate hybrid micelles have a spherical structure with a hydrodynamic diameter ranging from 80 to 120 nm depending on the amount of the incorporated tungstate.Keywords: Triblock Copolymer, Core-Shell-Corona, Tungstate, Hybrid Micelle, Stimuli-Responsive Micelle
Polymer Journal 04/2009; 41(6):492-497. · 1.26 Impact Factor
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ABSTRACT: Hollow metal oxide nanospheres, such as niobium pentoxide, cerium oxide, and vanadia, have been successfully synthesized, for the first time, by templating a polymeric micelle of poly(styrene-b-2-vinyl-1-methylpyridinium iodide-b-ethylene oxide) (PS-PVMP-PEO). PS-PVMP-PEO forms a micelle with a PS core, a PVMP shell, and a PEO corona in aqueous solutions. The significance of the present method is that each block of the copolymer has its unique function in the synthesis of hollow metal oxide nanospheres; the PS core plays the role of a template of the cavity, while the cationic PVMP shell works as a reservoir and nanoreactor for the precursors of the metal oxides and the PEO corona stabilizes the polymer/inorganic hybrid to prevent secondary aggregate formation.
Inorganic Chemistry 04/2009; 48(9):3898-900. · 4.60 Impact Factor
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ABSTRACT: Polymeric micelles from a new triblock copolymer, polystyrene-block-poly[(3-(methacryloylamino)propyl)trimethylammonium chloride]-block-poly(ethylene oxide) (PS-b-PMAPTAC-b-PEO), were prepared in aqueous solutions and characterized by various techniques including dynamic light scattering (DLS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and fluorescence spectroscopy. The micelle consists of a PS core, PMAPTAC shell, and PEO corona. It was revealed by SEM and DLS measurements that the micelles have a spherical structure with a hydrodynamic diameter about 75 nm. The addition of tungstate to the micellar solution caused a morphological change in the micelles from extended to shrunken spheres, which can be attributed to the fact that electrostatic repulsion among the cationic PMAPTAC blocks is canceled by the negative charge of the bound tungstate ions. Effective incorporation of tungstate ions into the micelles were confirmed by TEM and zeta-potential measurements.
Langmuir 01/2009; 25(2):739-43. · 4.19 Impact Factor
