f water

Addition of water and surfactant



Initiator and Segregation .

Initiator and Segregation .

Complets Engulfing

Partial Engulfintj

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Complets Engulfing

Partial Engulfintj

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Figure 9. (a) Scheme of formation of nanocapsules by miniemulsion polymerization and (b) TEM micrograph of nanocapsules of poly(styrene-co-acrylic acid) obtained by miniemulsion polymerization. After [391], F. Tiarks et al., Langmuir 17, 908 (2001). © 2001, American Chemical Society.

Figure 9. (a) Scheme of formation of nanocapsules by miniemulsion polymerization and (b) TEM micrograph of nanocapsules of poly(styrene-co-acrylic acid) obtained by miniemulsion polymerization. After [391], F. Tiarks et al., Langmuir 17, 908 (2001). © 2001, American Chemical Society.

releasing factor (GRF) formulation [392]. GRF can be associated with biodegradable poly(alkylcyanoacrylate) nano-particles. Among other parameters, the moment at which GRF was incorporated in the polymerization medium was found to be a critical factor in avoiding the degradation of GRF and the covalent bonding of the peptide with the polymer.

Biodegradable colloids suitable for use as drug delivery systems can be formed by in-situ polymerization of isobutyl-cyanoacrylate monomers. The mechanisms of formation of colloidal systems of polyisobutylcyanoacrylate (PIBCA) obtained in the presence of oil and ethanol were studied [393]. A polymerization system, a Winsor I-like system, was used for polymerization of styrene at room temperature [394]. The system consisted of a microemulsion (lower) phase that was topped off with styrene. The factors affecting the polymerization were discussed.

Plasma polymer thin films with encapsulated dye molecules (rhodamine 6G) and silver nanoparticles were deposited by alternating plasma polymerization, dye sublimation, and metal evaporation [395]. The interference between the optical absorption of the plasma polymer, the dye molecule absorption, and the plasma resonance absorption of the silver particles was measured in the UV-vis-near-infrared red spectral region. Fluorescence measurements demonstrated plasma polymer matrix effects on fluorescence of the dye molecules. Polymer thin films with embedded silver nanoparticles were deposited by simultaneous plasma polymerization and metal evaporation [396].

Silica (Aerosil A200 V) was functionalized by reaction with methacryloylpropyltrimethoxysilane (MPTMS) in toluene [397]. The grafting yield first increased with the ratio MPTMS/SiOH and then leveled off after full monolayer coverage, each molecule of MPTMS covering 7.1 nm. Silicone membranes with silica nanoparticles were prepared [398].

Inorganic Fe2O3 nanoparticles of 3-5 nm diameter were assembled with polymer microspheres and then encapsulated in copolymer of St/BA/AA by a polymerization process [399]. Fe2O3 encapsulated microspheres were obtained through interaction between surface groups of the two component particles and by adjusting the pH value in the emulsion. Pretreatment of the composite particles using a certain amount of surfactant before polymerization gave a good encapsulation.

Enzyme superoxide dismutase incorporation parameters were evaluated after immobilization in polyisobutylcyanoa-clylate nanoparticles [400]. After initialization of the anionic mechanism of polymerization, pH was increased and its effect on the characteristics of polyisobutylcyanoaclylate nanoparticles was analyzed. Optimization of enzyme activity during incorporation into nanoparticles and the influence on size distribution were studied.

Aiming at the preparation of nanometer-size polydiacety-lene microcrystals, the crystallization process during the reprecipitation method was investigated. An amorphous nanoparticle was formed initially and subsequently crystallized [401].

AB diblock copolymers consisting of poly(y-benzyl-L-glutamate) (PBLG) as the hydrophobic part and poly (N-isopropylacrylamide) (PNIPAAm) as the hydrophilic one were prepared by polymerization of y-benzyl-L-glutamate-N-carboxyanhydride (BLG-NCA) with semit-elechelic PNIPAAm with amino end group as initiator [402]. The core-shell type nanoparticles of the block copolymers were obtained by the diafiltration method. The sizes of the nanoparticles were from about 73 to 359 nm and the shapes of them were spherical.

Low-water-content reverse micelles were formed in cyclo-hexane employing Triton X-100 or AOT (bis(2-ethylhexyl) sulfosuccinate sodium (salt) as the surfactant [403]. At low water content, reverse micelles cannot properly solu-bilize polar species but the surfactant molecules tended to reorganize themselves around the polar molecules forming structures depending on the nature of the surfactant and the charge. Solid and hollow, magnetic and nonmagnetic, organic-inorganic monodispersed hybrid microspheres were synthesized [404].

Amphiphilic block copolymers are important in interface and particle stabilization. Mesophases and micelles of block copolymers and the solubilization and adhesion of amphiphilic block copolymers were considered [405]. ABtype amphiphilic copolymers composed of poly(L-leucine) as the A component and poly(ethylene oxide) as the B component were synthesized by the ring-opening polymerization of L-leucine N-carboxy-anhydride initiated by methoxy poly-oxyethylene amine [406]. Core-shell type nanoparticles were prepared by the diafiltration method. Micelles were formed also by a polystyrene/poly(vinylpyridine) copolymer. Nano-sized copper oxide particles dispersed in nylon 11 thin films were prepared by a thermal relaxation technique [407].

Conducting polymers and their processability problem were introduced, and the synthesis of an economically attractive and environmentally stable conducting polymer, viz., polyaniline in dispersion form, was discussed [408]. Nanoparticles of less than 20 nm in diameter were obtained from the particles in the dispersion by way of disintegrating them with the help of ultrasound. Nanoparticles produced inside of solutions of various matrix polymers underwent fractal aggregation.

An approach to prepare magnetic polymeric nanoparticles with narrow size distribution by synthesis of the magnetite core and polymeric shell in a single inverse microemulsion was reported [409]. The microemulsion seed copolymer-ization of methacrylic acid, hydroxyethyl methacrylate, and cross-linker resulted in a stable hydrophilic polymeric shell of the nanoparticles. The importance of three main parameters was emphasized in the nanostructured systems: the mechanical coupling between the two phases, the possible cross-linking of the macromolecules by the nanoparticles, and the connectivity between reinforcing particles [410].

Stable suspensions of superparamagnetic cobalt nano-particles were prepared in poly(dimethysiloxane) carrier fluids in the presence of poly[dimethylsiloxane-b-(3-cyanopropyl) methylsiloxane-b-dimethylsiloxane] triblock copolymers as steric stabilizers [411]. A series of polysilox-ane triblock copolymers with systematically varied molecular weights were prepared via anionic polymerization using LiOH as an initiator. These copolymers formed micelles in toluene and served as "nanoreactors" for thermal decomposition of the Co2(CO)8 precursor.

Latexes with a poly(dimethyl siloxane) core and a poly(styrene-methyl methacrylate-acrylic acid) shell were prepared in two steps in order to generate particles that have a core with a very low glass transition temperature [412]. In the first step, poly(dimethyl siloxane) particles were obtained via the ring-opening emulsion polymerization of octamethyl tetracyclosiloxane (D-4). The polymerization was carried out using either an anionic or a cationic catalyst. Using a PD4 latex as seed, a seeded emulsion polymerization of poly(styrene-methyl methacrylate-acrylic acid) was conducted to obtain core-shell particles.

Core-shell particles consisting of a polystyrene latex colloidal core and Fe2+metallosupramolecular polyelec-trolyte/poly(styrenesulfonate) multilayer shells were fabricated by the consecutive assembly of these polymers on polystyrene particles [413]. Structurally well-defined metallosupramolecular polyelectrolyte-colloid assemblies were studied, which combined the functional units from supramolecular chemistry with the restricted dimensionality of colloids.

The encapsulation of seed polymer particles coated by anionic iron oxide nanoparticles was investigated using N-isopropylacrylamide as a main monomer, N, N-methylene bisacrylamide as a cross-linking agent, itaconic acid as a functional monomer, and potassium persulfate as an anionic initiator [414].

Dispersion copolymerization of styrene and a poly(N-isopropylacrylamide) macromonomer in ethanol water media was carried out in the presence of AgNO3 [415]. Nanoscopic silver particles were generated on their surfaces via in-situ reduction of Ag+ by radicals generated from the initiator, 2, 2'-azobisisobutyronitrile. The particle sizes of both polystyrene microspheres and silver nanoparticles were affected by the initial 2, 2'-azobisisobutyronitrile, AgNO3, and macromonomer concentrations.

Monodisperse poly(4- and poly(2-vinylpyridine) nano-spheres in the 500 nm diameter range were prepared by emulsifier-free emulsion polymerization techniques under free radical initiation of the respective monomers with 4 wt% divinylbenzene as the cross-linking agent [416]. The size, integrity, and nature of the Pd-coated nanospheres were investigated.

The core-shell Y2O3:Eu3+/polystyrene particles were prepared by surface modification with citric acid and emulsion polymerization method with styrene [417]. The DTA curve of coated particles exhibits a small and wide exothermic peak of organic compound around 387 °C. The carbonyl stretching vibration band was shifted to low wavenumber in the Fourier transform IR (FTIR) spectrum and the binding energy of Y3d5/2 was shifted to the high-energy band in the X-ray photoelectron spectroscopy (XPS) spectrum.

Nanoporous carbons with extremely high mesopore volumes and surface areas were produced using silica nano-particles as templates [418]. The polymerization of resor-cinol and formaldehyde (RF) in the presence of silica sol particles generated RF gel-silica nanocomposites.

Uniform Ag nanowires were synthesized within nano-scale channels of mesoporous silica SBA-15 by a chemical approach, which involved AgNO3 impregnation followed by thermal decomposition [419].

The preparation, luminescent properties, and bioimaging applications of a novel zinc sulfide (core)-two-photon dye-silica (shell) multilayered heterostructure were reported

[420]. The method utilized reverse micelle synthesis involving multistep reactions as a result of which composite nano-particles having different sizes (typically 15-30 nm) and morphology were obtained. An increase in the luminescence intensity (similar to 70 times higher) and in fluorescence lifetime was observed for the dye encapsulated within the silica nanobubble.

Polymthyl methacrylate-based stealth and functional nanospheres, specifically designed for the reversible adsorption of oligonucleotides, were prepared by emulsion polymerization of methyl methacrylate in the presence of an ionic comonomer, namely a quaternary ammonium salt of 2-(dimethylamino)ethyl methacrylate, and a nonionic comonomer, namely a poly(ethylene glycol) methacrylate

[421]. The nanosphere size was substantially affected by the amount of both the nonionic and ionic comonomers.

Silaferrocenophanes fcSiMe2 and fcSi(CH2)3 [fc = Fe(%-C5H4)2] were incorporated into the well-ordered, hexagonal channels of mesoporous silica (MCM-41) [422]. Characterization of the composite materials indicated the presence of ring-opened monomer, oligomer, and polymer. From the magnetization data, the two phases were best described as Fe nanoparticles with diameters of 5.0-6.4 nm coated with a thin (ca. 0.4-0.6 nm) oxide layer.

A tripodal alkythiolate ligand was assembled on gold nanoparticles, which upon metathesis polymerization and particle etching yielded cross-linked spherical hollow polymer capsules [423]. Silver nanoparticles coated with a uniform, thin shell of titanium dioxide were synthesized via a one-pot route, where the reduction of Ag+ to Ag0 and the controlled polymerization of TiO2 on the surface of silver crystallites took place simultaneously [424]. High quality ultrathin films of the core-shell clusters were prepared via layer-by-layer assembly. The nanoparticles were arranged in closely packed layers interlaced with polyelectrolyte producing a stratified core-shell hybrid material with unique structure and catalytic and electron-transport properties.

Two polymethylmethacrylate functional nanosphere series, specifically designed for the reversible adsorption of oligonucleotides, were prepared by emulsion polymerization in the presence of two structurally different ionic comonomers, namely two quaternary ammonium salts of 2-(dimethylamino)ethyl methacrylate [425]. The nanosphere size was substantially affected by the ionic comonomer structure and amount. The width of the size distribution tended to decrease with increasing comonomer amount in solution, and monosized nanosphere samples were obtained at a high comonomer amount.

Copolymers of e-caprolactone and L-lactide with different monomer ratios were synthesized by ring-opening polymerization, and drug-loaded nanoparticles of poly-e-caprolactone, poly-L-lactide, and their copolymers were prepared by a precipitation method, respectively [426]. End-functionalized three-dimensional (3D) self-assembled monolayers on gold nanoparticles were used to initiate the living cationic ring-opening polymerization reaction directly on gold nanoparticle surfaces [427]. In this manner, dense polymer brushes were prepared in a "one-pot multistep" reaction.

Ultrasonic induced encapsulating emulsion polymerization was used to prepare the polymer/inorganic nanoparticle composites [428, 429]. The behaviors of several inorganic nanoparticles (SiO2, Al2O3, TiO2) under ultrasonic irradiation, such as dispersion, crushing, and activation, were studied. The dispersion stability, morphology, and structure of the ultrasonic irradiated nanoparticles were characterized. The inorganic nanoparticles in the aqueous solution can redisperse more effectively by ultrasonic irradiation than by conventional stirring. The well-dispersed nanoparticles were encapsulated by the formed polymer with thickness in the range of 5-65 nm.

Core-shell CdS/SiO2 nanoparticles were prepared and modified with the atom transfer radical polymerization initiator 3-(2-bromopropionyloxy) propyl dimethylethoxysi-lane [430]. The initiator-modified nanoparticles were then used as macroinitiators for the polymerization of methyl methacrylate catalyzed by NiBr2(PPh3)2.

The precipitation and condensation of submicrometer organic particles and the thermodynamic driving forces for precipitation and phase transformation were reviewed [431]. The importance of physical state effects was discussed, and the role of compartmentalization in controlling particle size was introduced. The use of emulsification as a primary step in producing small particle dispersions was illustrated with photographic and pharmaceutical applications.

Static and dynamic magnetic experiments were conducted on polymer-coated Fe nanoparticles of 15-20 nm synthesized by a microwave plasma method [432]. The field-dependent magnetization data showed the presence of sharp switching at low fields (about 60 Oe) followed by a gradual approach to a saturation magnetization of about 80 emu/g.

The effect of composition on the dispersion of Aux Cu1-x bimetallic nanoparticles into nylon 11 matrix was investigated [433]. The changes in the composition of the bimetallic particles arid in the depth distribution of the particles in the nylon 11 layer caused by heat treatment in N2 atmosphere were characterized. Islandlike bimetallic particles were found to be formed on the nylon 11 surface before heat treatment. By the heat treatment, the AuxCu1-x bimetallic particles with x < 0.55 were not dispersed into the nylon 11 layer while those with x > 0.70 were homogeneously dispersed in the films.

The preparation of hybrid organic/inorganic nano-composites comprised of well-defined polymers was reviewed [434]. Synthetic methods using controlled/"living" radical polymerization techniques, such as stable free radi-cal/ nitroxide-mediated polymerizations, atom transfer radical polymerization, and reversible addition-fragmentation chain-transfer polymerization, were described. The various approaches taken to prepare hybrid copolymers, nanoparticles, polymer brushes, dispersed silicate nano-composites, and nanoporous materials were discussed.

Polymer dispersions made of a variety of monomers, including styrene, butyl acrylate, and methyl methacrylate, were generated by the miniemulsion process in the presence of a coupling comonomer, a hydrophobe, and silica nanoparticles [435]. Depending on the reaction conditions and the surfactants employed, different hybrid morphologies were obtained, comprising a "hedgehog" structure where the silica surrounds the latex droplet and provides stabilization even without any low molecular weight surfactant.

Thermoresponsive, core-shell poly-N-isopropylacryl-amide nanoparticles (microgels) were synthesized by seed and feed precipitation polymerization, and the influence of chemical differentiation between the core and shell polymers on the phase transition kinetics and thermodynamics was examined [436]. The results suggested that the core-shell architecture is a powerful one for the design of colloidal "smart gels" with tunable properties. The addition of small concentrations of a hydrophobic monomer (butyl methacrylate) into the particle shell produced large decreases in the rate of thermoinduced particle collapse.

Silver nanoclusters in poly(methyl methacrylate) were prepared by bulk polymerization of methyl methacrylate with radical initiators (AIBN or BPO) in the presence of Ag+ trifluoroacetate, followed by a period of UV irradiation [437].

A versatile method for the generation of nanoparticu-late metals, ceramics, and polymers based on synthesis in miniemulsions—highly stable small droplets in a continuous phase—was presented [438]. In addition to nanoparticles, encapsulated materials, polymer capsules, and hollow particles can also be obtained by careful selection of the starting materials.

Melt mixing of nanoparticles with high performance polymers is not feasible due to severe shear heating and formation of particle aggregates. An alternative scheme was investigated involving the use of low molecular weight reactive solvents as processing aids and dispersion agents [439]. Dispersion of nanosize fumed silica particles in polyethersul-phone matrix was studied with the aid of small amounts of low molecular weight epoxy. Viscosity and processing temperatures of polyethersulphone were significantly reduced and fumed silica particles were dispersed to nanoscales.

A method was developed for the controlled release of the hydrophobic polymer chains from the core of the shell of cross-linked nanoparticles by selective cleavage of labile C-ON bonds present at the core-shell interface [440]. This represented a methodology to probe the permeability of nanoscopic membranes and a means for applications in the controlled release of macromolecular species.

A water-in-oil microemulsion method was applied for the preparation of silica-coated iron oxide nanoparticles [441]. Three different nonionic surfactants (Triton X-100, Igepal C0-520, and Brij-97) and pure water were used for the preparation of microemulsions, and their effects on the particle size, crystallinity, and the magnetic properties were studied.

The incorporation of CdS nanoparticles, prepared in reverse micellar systems, into thiol-modified mesoporous silica, such as functionalized MCM-41 and MCM-48, was investigated [442]. The nanoparticles were immobilized in the mesopores via the incorporation of water droplets of the reverse micelles.

An irradiation grafting method was applied for the modification of nanoparticles so that the latter can be added to polymeric materials for improving their mechanical performance, using existing compounding techniques. The following items were discussed: (a) chemical interaction between the grafting monomers and the nanoparticles during irradiation; (b) properties including modulus, yield strength, impact strength, and fracture toughness of the resultant nanocomposites; and (c) possible morphological changes induced by the addition of nanoparticles [443].

The coating of different materials with conducting electroactive polymers (i.e. polyaniline, polypyrrole, polythiophene, and their derivatives), provided by means of chemical polymerization, was reviewed [444]. The topics covered included the deposition of conducting electroac-tive polymers (i) by bulk oxidative chemical polymerization, (ii) by surface-located polymerization, and (iii) by coating of micro- and nanoparticles. The coating of different materials like polymers, polymer particles, ion-exchange membranes, glass, fiber, textile, soluble matrices, and inorganic materials was reviewed.

Chitosan-poly(acrylic acid) complex nanoparticles, which were well dispersed and stable in aqueous solution, were prepared by template polymerization of acrylic acid in chi-tosan solution [445]. The molecular weight of poly(acrylic acid) in nanoparticles increased with increasing molecular weight of chitosan, indicating that the polymerization of acrylic acid in the chitosan solution was a template polymerization. The prepared nanoparticles carried a positive charge and showed a size in the range from 50 to 400 nm. The surface structure and £ potential of nanoparticles were controlled by different preparation processes. The potential of chitosan as an emulsion stabilizer was combined with the miniemulsion technique to generate oil droplets, hollow capsules, and latex particles in the diameter range of 100-300 nm carrying a functional biopolymer surface [446]. Facile fabrication of hollow polystyrene nanocapsules was done by microemulsion polymerization [447].

Liquid nanodroplets within a size range of 50 to 500 nm were prepared by shearing a system containing oil, water, and a surfactant [448]. The growth of the nanodroplets can effectively be suppressed by using a strong hydrophobe as an additive to the oil and an effective surfactant. The hydrophobe acted as an osmotic agent which stabilized the system against Ostwald ripening. The growth of the droplets by collision was controlled by the density of the surfactant layer. Freshly prepared miniemulsions were "critically stabilized" and show a slow but pronounced growth, whereas a miniemulsion in "equilibrium" exhibited constant droplet size on longer time scales.

Surface-initiated living free radical polymerization was employed in a multistep procedure to prepare hollow polymeric nanocapsules [449]. Initially, trichlorosilyl-substituted alkoxyamine initiating groups were attached to the surface silanol groups of silica nanoparticles. This surface layer of initiating groups was then used to grow functionalized linear chains leading to a core-shell morphology. Under either chemical or thermal conditions, the reaction of these functionalities gave a cross-linked polymeric shell that was covalently attached to, and surrounded, the central silica core. Removal of the silica core then gave the hollow polymeric nanocapsules, which were stable under solvent dissolution and thermal treatment because of their cross-linked structure.

Electron affinities of methyl-2-cyanoacrylate and ethyl-2-cyanoacrylate were predicted using four different density functional or hybrid Hartree-Fock/density functional methods [450]. Equilibrium structures and harmonic vibrational frequencies were computed for the neutral and anionic species of each system.

The protective antioxidant role of idebenone both as free drug and drug-loaded Tween 80-coated polyethyl-2-cyanoacrylate nanocapsules was reported [451]. The relationship] between oxidative damage and apoptotic or nonapoptotic cell death was evaluated in vitro.

A synthetic process for producing aromatic polycarbonate nanoparticles using supercritical CO2 was developed [452]. High molecular weight polycarbonate nanoparticles were synthesized using transesterification between bisphenol-A and diphenyl carbonate in supercritical CO2 which was an excellent plasticizing agent and a good solvent for phenol, a by-product of the reaction. Poly(propylene oxide)-poly(ethylene oxide)-poly(propylene oxide) tri-block copoly-mer with CO2-phobic anchor and CO2-philic tail group was used as a stabilizer for the preparation of stable dispersions of bisphenol-A-diphenyl carbonate mixture in a CO2 continuous phase. The resulting polycarbonate particles with a nanosize of 30-140 nm had a high molecular weight of 3.1 x 105 (g/mol).

Functional arborescent graft polystyrenes prepared by a technique involving the iterative grafting of end functional polymer chains onto reactive polymer backbones were synthesized [453]. The zero-generation comb polymers and then the first generation hyperbranched structures were obtained by the coupling reaction of living (x-acetal polystyryllithium) onto linear or comb chains of poly(chloro ethyl vinyl ether) of controlled (DP) over bar (n) and structure.

A type of narrowly dispersed fluorescent cross-linked polystyrene nanoparticle (20-50 nm) was synthesized via a modified microemulsion copolymerization of styrene, cross-linker divinyl benzene, and a hydrophilic comonomer amino ethyl methacrylate hydrochloride, in the presence of pyrene [454]. Characterized by steady-state fluorescence spectra, these nanoparticles showed high luminescent intensity and the embedded pyrene had a negligible desorption from the nanoparticles.

Core-shell polymeric nanoparticles were prepared by self-assembly and step-growth polymerization [455]. An approach was presented for the controlled intramolecular collapse of linear polymer chains to give well-defined single-molecule nanoparticles whose structure was directly related to the original linear polymer [456]. By employing a combination of living free radical polymerization and benzocyclobutene chemistry, nanoparticles can be routinely prepared in multigram quantities with the size being accurately controlled by either the initial degree of polymerization of the linear chain or the level of incorporation of the benzocyclobutene coupling groups. The latter allowed the cross-link density of the final nanoparticles to be manipulated.

Stable colloidal solutions of gold nanoparticles surface-derivatized with a thiol monolayer were prepared using two-phase (water-nitrobenzene) reduction of AuCl4-by sodium borohydride in the presence of 2-mercapto-3-n-octylthiophene [457]. This kind of surface-functionalized gold nanoparticle was incorporated into the poly(3-octylthio phene) films on electrode in the process of electrochemical polymerization leading to poly(3-octyl thiophene)-gold nanoparticle composite films.

Polyphenylpyrrole coated silver nanoparticles at the liquid/liquid interface were produced [458]. In the electrochemical step of the reaction, N-phenylpyrrole facilitated the transfer of the silver ion from an aqueous to an organic phase. This step was followed by a slow homogeneous electron transfer reaction from the N-phenylpyrrole to the silver ion followed by polymerization and metal cluster growth.

Inorganic silica nanoparticles were encapsulated with an epoxy resin to give waterborne nanocomposite dispersions, using the phase-inversion emulsification technique [459]. Submicrometer-sized waterborne particles with narrow size distribution were prepared. All the silica nanoparticles were encapsulated within the composites and uniformly dispersed therein. Curing of the nanocomposite dispersions proceeded in a controlled manner.

A ternary microemulsion polymerization was used to prepare nanosized hollow polystyrene microlatexes with triblock copolymers of poly(oxyethylene)-poly(oxypropylene)-poly (oxyethylene) [(EO)X(PO)y(EO)X] [460]. Micelle formation using triblock copolymers was a useful nanoreactor in order to make polymer nanoparticles in o/w microemul-sions. Poly(methyl methacrylate)/cross-linked polystyrene core/shell nanospheres were fabricated by o/w microemulsion. Polystyrene hollow nanospheres were obtained using the polymer core etching technique. The size of the hollow nanoparticle was dependent on the surfactant concentration and the weight ratio of [surfactant]/[monomer].

Drug delivery systems had a great impetus to deliver a drug to diseased lesions. A suitable carrier was needed to deliver a suitable and sufficient amount of the drug to a targeted point; hence various kinds of formulations were developed. The state of the art was reviewed regarding the synthetic methods and characterization of nanoparticles, the suitability of polymeric systems for various drugs, drug loading, and drug release properties of various systems such as nanoparticles, hydrogels, microspheres, film and membranes, tablets, etc. [461].

An overview was given on the mechanisms of formation of polymerization in miniemulsions, the synthesis of new polymers, and dispersive hybrid systems from heterophase situations [462].

The in-situ formation of Au/Pt bimetallic nanoparticles on the surface of polystyrene microspheres was reported [463]. This was accomplished by dispersion copolymerization of styrene and a poly(N-isopropylacrylamide) macromonomer in ethanol-water media in the presence of HAuCl4 and H2PtCl6. The particle size and morphology of the polystyrene microspheres were changed by varying the molar ratio of Au/Pt. The propagation of oligomer radicals and nucleation of polystyrene microspheres were controlled by the Au/Pt molar ratio.

Nanometer-sized CoPt particles dispersed in a poly(methyl methacrylate) matrix were prepared, as a novel nanostructured magnetic plastic, through a soft chemical processing route [464]. CoPt nanoparticles were synthesized from a solution phase reduction system in the presence of capping ligands and stabilizing agents at high temperature. The CoPt nanoparticles were annealed at 400 °C for 3 h and were subsequently redispersed in methylmethacrylate (monomer).

To study interfacial particle-to-particle bonding mechanisms, an ultrathin film of pyrrole was deposited on alumina nanoparticles using a plasma polymerization treatment [465]. A thin film of the pyrrole layer (2 nm) was uniformly deposited on the surfaces of the nanoparticles. Particles of all sizes (10-150 nm) exhibited equally uniform ultrathin films indicating well-dispersed nanoparticles in the fluidized bed during the plasma treatment. The pyrrole-coated nano-particles were consolidated at a temperature range (approximately 250 °C).

The synthesis and characterization of well-dispersed, CoFe2O4 nanoparticles within a polymer matrix at room temperature were reported [466]. Comparable inorganic synthetic methods required heating at high temperatures in order to produce this particular mixed-metal oxide composition. The modification of templating schemes using block copolymers consisted of introducing a mixture of metal salts to a polymer solution before any microphase separation of the block copolymer constituents can occur, thus allowing fast diffusion of metals to the functional polymer backbone. The diblock copolymer matrix was synthesized using ring-opening metathesis polymerization of norbornene derivatives.

The preparation and evaluation were reported of cyclo-phosphamide loaded-polyalkylcyanoacrylate nanospheres obtained by emulsion polymerization [467]. Nanoparticles of improved stability against long-term aggregation were prepared using poly(styrene)b-poly(2-vinylpyridine) star-block copolymer architectures [468]. The star-block copolymers, physically resembling diblock copolymer micelles, were synthesized by anionic polymerization and coupling with ethy-lene glycol dimethacrylate.

Catalytic sites can be placed at the core, at interior positions, or at the periphery of a dendrimer. There are many examples of the use of peripherally functionalized dendrimers in catalysis. A review was concerned with dendrimer-based catalysis involving catalytic sites at the core of a dendrimer and within the interior voids [469]. Key features were positive and/or negative catalytic activity.

The synthesis and applications of organic-inorganic nanostructured colloids and colloidal-based materials were reviewed [470]. Emphasis was placed on the strategies and synthetic methods developed to organize organic-inorganic architectures. A description and a general hierarchical classification of different systems were given from inorganic particle synthesis and surface modification to more elaborate nanostructured colloids obtained through in-situ encapsulation and/or self-assembly techniques. Ordering of colloids into two- and three-dimensional arrays and their use as templates was considered. Some properties and applicability of organic-inorganic colloids in catalysis, medicine, and coating technologies were cited.

The photoinduced flocculation of a nonaqueous dispersion of core-shell nanoparticles (diameter = 50 nm) was described [471]. The particles consist of a tightly cross-linked core composed of poly(butyl methacrylate-co-ethylene gly-col dimethacrylate) and a lightly cross-linked shell of poly(butyl methacrylate-co-ethylene glycol dimethacrylate-co-methacrylic acid). The process of particle aggregation kinetics was studied in the absence of long-range electrostatic interaction by using a combination of static and dynamic laser light scattering.

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