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Spherical Micelles (spherical + micelle)
Selected AbstractsStudy on the Radius of an Electrical Spherical Micelle: Functional Theoretical ApproachCHINESE JOURNAL OF CHEMISTRY, Issue 4 2004Zheng-Wu Wang Abstract For the purpose of eliminating restriction, the Poisson-Boltzmann (PB) equation, which represents the potential of the electrical double layer of spherical micelles, can be solved analytically only under the lower potential condition, a kind of iterative method in functional analysis theory has been used. The radius of the spherical particle can be obtained from the diagram of the second iterative solution of the potential versus the distance from the center of the particle. The influences of the concentration of the ions, the charge number of ions, the aggregation number of the particle, the dielectric constant of solvent and the temperature of system on the radius also have been studied. [source] Nanometer-Scaled Hollow Spherical Micelles with Hydrophilic Channels and the Controlled Release of IbuprofenMACROMOLECULAR RAPID COMMUNICATIONS, Issue 23 2008De'an Xiong Abstract PS- b -PAA spherical micelles with a liquid core and a PAA shell are prepared with the assistance of 1,2-dichloroethane. During the process of adding a mixture of PNIPAM- b -P4VP and PEG- b -P4VP, multi-layered micelles with a mixed corona that consists of both PNIPAM and PEG chains are constructed through the electrostatic interaction and hydrogen bonding between the PAA block and the P4VP block. When heating above the LCST, the PNIPAM chains collapse onto the PAA/P4VP complex layer while the PEG chains still stretch into the solution through the collapsed PNIPAM layer, which leads to the formation of hydrophilic channels around the PEG chains. The ibuprofen encapsulated in the hollow space can diffuse through the channels and its release rate can be controlled by changing the ratio of PEG chains to PNIPAM chains in the corona. [source] Conducting and Superhydrophobic Rambutan-like Hollow Spheres of Polyaniline,ADVANCED MATERIALS, Issue 16 2007Y. Zhu Superhydrophobic polyaniline (PANI) hollow spheres (see figure and cover) with high conductivity were self-assembled by using perfluorooctane sulfuric acid (PFOSA) as both dopant and soft template. It is proposed that these spheres are formed by a co-operative effect of two self-assembly processes: spherical micelles composed of PFOSA serve as a "microreactor" and PFOS/aniline salt micelles act as the soft template of the PANI nanofibers. [source] A Micellar Approach to Magnetic Ultrahigh-Density Data-Storage Media: Extending the Limits of Current Colloidal Methods,ADVANCED MATERIALS, Issue 3 2007A. Ethirajan An alternative route for producing L10FePt nanoparticles based on the self-organization of diblock copolymers into spherical micelles is presented. It overcomes all of the drawbacks of current colloidal strategies towards densely packed arrays of ferromagnetic FePt nanoparticles while still guaranteeing areal densities exceeding 1,Tbits,inch,2. The figure shows a sketch of the metal-salt-loaded micelles deposited on a substrate: a polystyrene shell (red) covers the poly(2-vinylpyridine) core (blue) forming a nanoreactor loaded with metal salt (yellow). [source] Micellar behavior of well-defined polystyrene-based block copolymers with triethoxysilyl reactive groups and their hydrolysis,condensationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 4 2010Cé Guinto Gamys Abstract Block copolymers of acryloxy propyl triethoxysilane and styrene were prepared through nitroxide-mediated polymerization using alkoxyamine initiators based on N - tert -butyl-1-diethylphosphono-2,2-dimethylpropyl nitroxide. The copolymers were characterized by 1H NMR, size exclusion chromatography and differential scanning calorimetry. Their micellar behavior in dioxane/methanol solutions was examined through static light scattering and transmission electron microscopy (TEM). TEM indicated the successful formation of spherical micelles which were subsequently frozen by the sol,gel process. Hydrolysis,condensation of the reactive ethoxysilyl side groups was followed by FTIR, 1H NMR, and 29Si NMR. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 784,793, 2010 [source] Self-assembly of well-defined amphiphilic polymeric miktoarm stars, dendrons, and dendrimers in water: The effect of architectureJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 22 2009Daria E. Lonsdale Abstract Five polymeric architectures with a systematic increase in architectural complexity were synthesized by "click" reactions from a toolbox of functional linear polymers and small molecule linkers. The amphiphilic architectures ranged from a simple 3-miktoarm star block copolymer to the more complex third generation dendrimer-like block copolymer, consisting of polystyrene (PSTY) and polyacrylic acid (PAA). Micellization of these architectures in water at a pH of 7 under identical ionic strength gave spherical micelles ranging in size from 9 to 30 nm. Subsequent calculations of the PSTY core density, average surface area per PAA arm on the corona-core interface, and the relative stretching of the PAA arms provided insights into the effect of architecture on the self-assembly processes. A particular trend was observed that with increased architectural complexity the hydrodynamic diameter, radius of the core in the dry state and the aggregation number also increased with the exception of the third generation dendrimer. On the basis of these observations, we postulate that thermodynamic factors controlling self-assembly were the entropic penalty of forming PSTY loops in the core counterbalanced by the reduction in repulsive forces through chain stretching. This results in a greater number of aggregating unimers and consequently larger micelle sizes. The junction points within the architecture also play an important role in controlling the self-assembly process. The G3 dendrimer showed results contradictory to the aforementioned trend. We believe that the self-assembly process of this architecture was dominated by the increased attractive forces due to stretching of the PSTY core chains to form a more compact core. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6292,6303, 2009 [source] Amphiphilic gradient copolymers containing fluorinated 2-phenyl-2-oxazolines: Microwave-assisted one-pot synthesis and self-assembly in waterJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 17 2008Matthias Lobert Abstract Here, we present the one-step synthesis of 2-(m -difluorophenyl)-2-oxazoline and its use as a monomer for microwave-assisted statistical cationic ring-opening copolymerizations (CROP). Well-defined amphiphilic gradient copolymers, as evidenced by the polymerization kinetics, were prepared using 2-ethyl-2-oxazoline as comonomer and methyl tosylate as initiator in nitromethane at 140 °C. The resulting gradient copolymers (DP = 60 and 100) were characterized by means of size exclusion chromatography and 1H NMR spectroscopy. In the second part, we focus on a detailed study of the self-assembly of the copolymers in aqueous solution using atomic force microscopy and dynamic light scattering. Both methods revealed the self-assembly of the gradient copolymers into spherical micelles. To quantify the influence of the fluorine atoms and the monomer distribution on the self-assembly, a comparative study with gradient copolymers of 2-phenyl-2-oxazoline and 2-ethyl-2-oxazoline was performed. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5859,5868, 2008 [source] Synthesis and self-assembly of helical polypeptide-random coil amphiphilic diblock copolymerJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 9 2008Shiao-Wei Kuo Abstract Three amphiphilic rod-coil diblock copolymers, poly(2-ethyl-2-oxazoline- b -,-benzyl- L -glutamate) (PEOz- b -PBLG), incorporating the same-length PEOz block length and various lengths of their PBLG blocks, were synthesized through a combining of living cationic and N -carboxyanhydride (NCA) ring-opening polymerizations. In the bulk, these block copolymers display thermotropic liquid crystalline behavior. The self-assembled aggregates that formed from these diblock copolymers in aqueous solution exhibited morphologies that differed from those obtained in ,-helicogenic solvents, that is, solvents in which the PBLG blocks adopt rigid ,-helix conformations. In aqueous solution, the block copolymers self-assembled into spherical micelles and vesicular aggregates because of their amphiphilic structures. In helicogenic solvents (in this case, toluene and benzyl alcohol), the PEOz- b -PBLG copolymers exhibited rod-coil chain properties, which result in a diverse array of aggregate morphologies (spheres, vesicles, ribbons, and tube nanostructures) and thermoreversible gelation behavior. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3108,3119, 2008 [source] Poly(,-caprolactone)- b -poly(ethylene glycol)- b -poly(,-caprolactone) triblock copolymers: Synthesis and self-assembly in aqueous solutionsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 4 2007Yaqiong Zhang Abstract Nontoxic and biodegradable poly(,-caprolactone)- b -poly(ethylene glycol)- b -poly(,-caprolactone) triblock copolymers were synthesized by the solution polymerization of ,-caprolactone in the presence of poly(ethylene glycol). The chemical structure of the resulting triblock copolymer was characterized with 1H NMR and gel permeation chromatography. In aqueous solutions of the triblock copolymers, the micellization and sol,gel-transition behaviors were investigated. The experimental results showed that the unimer-to-micelle transition did occur. In a sol,gel-transition phase diagram obtained by the vial-tilting method, the boundary curve shifted to the left, and the gel regions expanded with the increasing molecular weight of the poly(,-caprolactone) block. In addition, the hydrodynamic diameters of the micelles were almost independent of the investigated temperature (25,55 °C). The atomic force microscopy results showed that spherical micelles formed at the copolymer concentration of 2.5 × 10,4 g/mL, whereas necklace-like and worm-like shapes were adopted when the concentration was 0.25 g/mL, which was high enough to form a gel. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 605,613, 2007 [source] Amphiphilic star-block copolymers based on a hyperbranched core: Synthesis and supramolecular self-assemblyJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 24 2005Zhifeng Jia Abstract Novel amphiphilic star-block copolymers, star poly(caprolactone)- block -poly[(2-dimethylamino)ethyl methacrylate] and poly(caprolactone)- block -poly(methacrylic acid), with hyperbranched poly(2-hydroxyethyl methacrylate) (PHEMA,OH) as a core moiety were synthesized and characterized. The star-block copolymers were prepared by a combination of ring-opening polymerization and atom transfer radical polymerization (ATRP). First, hyperbranched PHEMA,OH with 18 hydroxyl end groups on average was used as an initiator for the ring-opening polymerization of ,-caprolactone to produce PHEMA,PCL star homopolymers [PHEMA = poly(2-hydroxyethyl methacrylate); PCL = poly(caprolactone)]. Next, the hydroxyl end groups of PHEMA,PCL were converted to 2-bromoesters, and this gave rise to macroinitiator PHEMA,PCL,Br for ATRP. Then, 2-dimethylaminoethyl methacrylate or tert -butyl methacrylate was polymerized from the macroinitiators, and this afforded the star-block copolymers PHEMA,PCL,PDMA [PDMA = poly(2-dimethylaminoethyl methacrylate)] and PHEMA,PCL,PtBMA [PtBMA = poly(tert -butyl methacrylate)]. Characterization by gel permeation chromatography and nuclear magnetic resonance confirmed the expected molecular structure. The hydrolysis of tert -butyl ester groups of the poly(tert -butyl methacrylate) blocks gave the star-block copolymer PHEMA,PCL,PMAA [PMAA = poly(methacrylic acid)]. These amphiphilic star-block copolymers could self-assemble into spherical micelles, as characterized by dynamic light scattering and transmission electron microscopy. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6534,6544, 2005 [source] Poly(3,4-ethylenedioxythiophene) Nanospheres Synthesized Using a Micelle Soft Template Associated with Cuprous OxideMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 11 2010Ying Zhu Abstract PEDOT nanospheres with an average diameter of about 100,nm were chemically synthesized using APS as the oxidant in the presence of SDBS and Cu2O, respectively. It was found that Cu2O is crucial to forming uniform PEDOT nanospheres because only granular PEDOT was obtained in the absence of Cu2O. It is proposed that the PEDOT nanospheres are self-assembled by a cooperation effect of SDBS as the micelle soft-template and Cu2O as the stabilizer of the spherical micelles. Additionally, the PEDOT nanospheres are soluble in some organic solvents, such as THF, DMF and DMSO, which is of benefit for fabrication of electronic and photonic devices. [source] Sphere-to-Rod Transition of Micelles formed by the Semicrystalline Polybutadiene- block -Poly(ethylene oxide) Block Copolymer in a Selective SolventMACROMOLECULAR RAPID COMMUNICATIONS, Issue 5 2010Adriana M. Mihut Abstract We present a morphological study of the micellization of an asymmetric semicrystalline block copolymer, poly(butadiene)- block -poly(ethylene oxide), in the selective solvent n -heptane. The molecular weights of the poly(butadiene) (PB) and poly(ethylene oxide) (PEO) blocks are 26 and 3.5,kg,·,mol,1, respectively. In this solvent, micellization into a liquid PEO-core and a corona of PB-chains takes place at room temperature. Through a thermally controlled crystallization of the PEO core at ,30,°C, spherical micelles with a crystalline PEO core and a PB corona are obtained. However, crystallization at much lower temperatures (,196,°C; liquid nitrogen) leads to the transition from spherical to rod-like micelles. With time these rod-like micelles aggregate and form long needles. Concomitantly, the degree of crystallinity of the PEO-cores of the rod-like micelles increases. The transition from a spherical to a rod-like morphology can be explained by a decrease of solvent power of the solvent n -heptane for the PB-corona chains: n -Heptane becomes a poor solvent at very low temperatures leading to a shrinking of the coronar chains. This favors the transition from spheres to a morphology with a smaller mean curvature, that is, to a cylindrical morphology. [source] Nanometer-Scaled Hollow Spherical Micelles with Hydrophilic Channels and the Controlled Release of IbuprofenMACROMOLECULAR RAPID COMMUNICATIONS, Issue 23 2008De'an Xiong Abstract PS- b -PAA spherical micelles with a liquid core and a PAA shell are prepared with the assistance of 1,2-dichloroethane. During the process of adding a mixture of PNIPAM- b -P4VP and PEG- b -P4VP, multi-layered micelles with a mixed corona that consists of both PNIPAM and PEG chains are constructed through the electrostatic interaction and hydrogen bonding between the PAA block and the P4VP block. When heating above the LCST, the PNIPAM chains collapse onto the PAA/P4VP complex layer while the PEG chains still stretch into the solution through the collapsed PNIPAM layer, which leads to the formation of hydrophilic channels around the PEG chains. The ibuprofen encapsulated in the hollow space can diffuse through the channels and its release rate can be controlled by changing the ratio of PEG chains to PNIPAM chains in the corona. [source] Synthesis and Characterization of Helix-Coil Diblock Copolymers with Controlled Supramolecular Architectures in Aqueous Solution,MACROMOLECULAR RAPID COMMUNICATIONS, Issue 15 2005Jie Zhang Abstract Summary: A series of helix-coil diblock copolymers based on poly(ethylene oxide) and optically active helical poly{(+)-2,5-bis[4,-((S)-2-methylbutoxy)phenyl]styrene} (PMBPS) were synthesized via atom transfer radical polymerization (ATRP). The synthetic methodology permitted straightforward preparation of the diblock copolymers with relatively low polydispersities and a broad range of compositions and molecular weights. Depending on the composing block length and the initial concentration, the copolymers self-assembled into different supramolecular structures in aqueous solution, including spherical micelles, vesicles, multilamellar vesicles, large compound vesicles, and tubules. Schematic representation of the synthesis of PEO- b -PMBPS block copolymers and their aggregation in aqueous solution. [source] Nanostructured thermosets from self-assembled amphiphilic block copolymer/epoxy resin mixtures: effect of copolymer content on nanostructuresPOLYMER INTERNATIONAL, Issue 4 2010Miren Blanco Abstract Nanostructure formation in thermosets can allow the design of materials with interesting properties. The aim of this work was to obtain a nanostructured epoxy system by self-assembly of an amphiphilic diblock copolymer in an unreacted epoxy/amine mixture followed by curing of the matrix. The copolymer employed was polystyrene- block -poly(methyl methacrylate) (PS- b -PMMA). The thermoset system, formed by a diglycidyl ether of bisphenol A-type epoxy resin and diaminodiphenylmethane hardener, was chosen to ensure the miscibility of most of the PMMA block until matrix gelation. Transparent materials with microphase-separated domains were obtained for copolymer contents lower than 40 wt%. In systems containing 20 and 30 wt% block copolymer, the PS block formed spherical micelles or worm-like structures before curing, which were stabilized through curing by the more compatible PMMA block phase. Nanostructured thermoset systems were successfully synthesized for self-assembled amphiphilic block copolymer,epoxy/amine mixtures for copolymer contents lower than 40 wt%. Copyright © 2009 Society of Chemical Industry [source] Solution self-assembly of tailor-made macromolecular building blocks prepared by controlled radical polymerization techniquesPOLYMER INTERNATIONAL, Issue 9 2006Jean-François Lutz Abstract This review describes the preparation of colloidal aggregates (spherical micelles, cylindrical micelles, polymer vesicles, multicompartment micelles, polyion complexes, schizophrenic micelles) using bottom-up self-assembly approaches. In particular, it focuses primarily on the self-organization of well-defined macromolecular building blocks (macrosurfactants, polysoaps, polyelectrolytes) synthesized by controlled radical polymerization techniques such as atom transfer radical polymerization, reversible addition fragmentation transfer polymerization and nitroxide-mediated polymerization. The goal of this review is to highlight that these versatile techniques of polymer synthesis allow the preparation of unprecedented nanostructures in dilute solutions. Copyright © 2006 Society of Chemical Industry [source] Small angle neutron scattering study of the structure and hydration of polyoxyethylene- block -polyoxybutylene in aqueous solutionPOLYMER INTERNATIONAL, Issue 7 2006J Patrick A Fairclough Abstract The micellar structure of a polyoxyethylene- block -polyoxybutylene diblock copolymer (E18B10; E = (OCH2CH2); B = OCH2CH(CH2CH3)) in water was studied by small angle neutron scattering. Results show a polydisperse spherical micelles at temperatures below 45 °C, a possible mixed phase at 45 °C and flexible worm-like micelles at 65 °C. The spherical micelles at 25 and 35 °C have radii of 39 and 40 Å and degrees of hydration of 28% and 26%, respectively. The worm-like micelles have a total length of approximately 1850 Å, with segment lengths of 123 Å, a core radius, Rax = 30 Å and hydration of 23%, at 65 °C. Copyright © 2006 Society of Chemical Industry [source] General Synthesis and Aggregation Behaviour of New Single-Chain Bolaphospholipids: Variations in Chain and Headgroup StructuresCHEMISTRY - A EUROPEAN JOURNAL, Issue 22 2008Simon Drescher Abstract The chemical structures of polymethylene-1,,-bis(phosphocholines) that self-assemble into nanofibres was modified on the one hand in the hydrophobic chain region, by introduction of sulfur and oxygen atoms, and on the other hand by variation of the polar headgroup structure with functionalised tertiary amines. The temperature-dependent self-assembly of these novel bolaphospholipids into nanofibres and spherical micelles was investigated by differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). The thermal stabilities of the nanofibres strongly depend on the chemical compositions of the headgroups and of the hydrophobic chains. The insertion of new functionalities in the headgroup region by click chemistry makes these substances interesting for potential applications in bioscience and materials science. [source] Study on the Radius of an Electrical Spherical Micelle: Functional Theoretical ApproachCHINESE JOURNAL OF CHEMISTRY, Issue 4 2004Zheng-Wu Wang Abstract For the purpose of eliminating restriction, the Poisson-Boltzmann (PB) equation, which represents the potential of the electrical double layer of spherical micelles, can be solved analytically only under the lower potential condition, a kind of iterative method in functional analysis theory has been used. The radius of the spherical particle can be obtained from the diagram of the second iterative solution of the potential versus the distance from the center of the particle. The influences of the concentration of the ions, the charge number of ions, the aggregation number of the particle, the dielectric constant of solvent and the temperature of system on the radius also have been studied. [source] | |||||||||||||