Nanoparticles amphiphilic micellar

Here, the distinct domains of the resulting hybrid polymer are responsible for the self-assembly of the material. It should be noted that there are several other approaches to nanomaterials via ROMP, including the synthesis of dispersed latex nanoparticles, [29-34] hybrid nanoparticles via scaffolded initiation [35-39], and nanoparticles encapsulated in polymer matrices [40,41]. Amphiphilic micellar nanoparticles are by far the most prevalent systems in the literature relevant to a discussion of ROMP in nanoparticle synthesis, particularly those fully characterized in terms of particle formation and morphological characterization of the resulting polymer aggregates. Amphiphilic copolymers synthesized by ROMP that are not studied in this manner [42-45] or those nanoscale architectures involving only covalent interactions [46, 47] are not discussed here. 

Due to it s highly efficient and orthogonal nature, copper-catalyzed click chemistry is an attractive route to post-polymerization functionalization of ROMP copolymer backbones yielding amphiphilic micellar nanoparticles [103, 104]. However, it should be noted that post polymerization modification is necessary to yield azide or acetylene modified polymers, as azide and acetylene functionalities are not compatible with current ROMP catalysts. Ohe and coworkers [104] have synthesized amphiphihc triblock copolymers capable of assembly into discrete micellar nanoparticles by clicking an acetylene-modified hexaethylene... 

Kim W, Thevenot J, Ibarboure E et al (2010) 5elf-assembly of thermally responsive amphiphilic diblock copolypeptides into spherical micellar nanoparticles. Angew Chem Int Ed 49 4257 260... 

Starblock (or radial star) copolymers form another kind of amphiphilic nanoparticles which can be regarded as unimolecular micelles. Alternatively, cylindrical core-shell brushes can be regarded as unimolecular cylinder micelles. Due to the covalent attachment of the block copolymers at one end, frustrated micellar structures can be made which would never form spontaneously. The cylindrical systems will be reviewed in Sect. 4.2. 

Particles of the enzymatically synthesized phenolic polymers were also formed by reverse micellar polymerization. A thiol-containing polymer was synthesized by peroxidase-catalyzed copolymerization of p-hydroxythiophenol and p-ethylphenol in reverse micelles [70], CdS nanoparticles were attached to the copolymer to give polymer-CdS nanocomposites. The reverse micellar system was also effective for the enzymatic synthesis of poly(2-naphthol) consisting of qui-nonoid structure [71], which showed a fluorescence characteristic of the naphthol chromophore. Amphiphilic higher alkyl ester derivatives were enzymatically polymerized in a micellar solution to give surface-active polymers at the air-water interface [72, 73]. 

Toshiba and Takahashi [214] prepared nanoparticles of colloidal Pt embedded in a micelle (Fig. 18.22). With such a system the initial rate of hydrogenation of 2-undecenoic acid is almost 6 times lower than the initial rate of hydrogenation of 10-undecenoic acid. The explanation is based on the polar effect of the amphiphilic ligand whose polar head stays outside the particle. The polar head fadhtates the coordination of the double bond by preventing the carboxyUc function from approaching the surface of Pt but considering such a micellar system, one can see easily their fragility. 

Conticello and colleagues have studied the potential of amphiphilic diblock (AB) and triblock (ABA) elastin-like copolymers, where A is a hydrophilic and B a hydrophobic block, to reversibly self-assemble into well-defined micellar aggregates (20,30). Collapse of the hydrophobic block above Tt results in the formation of elastin-based nanoparticles. To provide diversity in the mechanical properties of the micellar structures, the amino acid sequence of the hydrophobic block was varied between plastic (VPAVG) and elastomeric (VPGVG) in nature. The hydrophilic block is designed to maintain solubility and form a protective core that prevents protein adsorption and clearance by the reticuloendothelial system. 

Recently, Miller and Cacciuto explored the self-assembly of spherical amphiphilic particles using molecular dynamics simulations [46]. They found that, as well as spherical micellar-type structures and wormlike strings, also bilayers and faceted polyhedra were possible as supracolloidal structures. Whitelam and Bon [47] used computer simulations to investigate the self-assembly of Janus-like peanut-shaped nanoparticles and found phases of clusters, bilayers, and non-spherical and spherical micelles, in accordance with a packing parameter that is used conventionally and in analogy to predict the assembled structures for molecular surfactants. They also found faceted polyhedra, a structure not predicted by the packing parameter (see Fig. 8). In both studies, faceted polyhedra and bilayers coexist, a phenomenon that is still unexplained. 

Payyappilly, S.S., Dhara, S., Chattopadhyay, S. The heat-chill method for preparation of self-assembled amphiphilic poly (e-caprolactone)-poly (ethylene glycol) block copolymer based micellar nanoparticles for drug delivery. Soft Matter 10, 2150—2159. 

Figm 13 (a) Sequence and schematic representation of the self-assembly of an amphiphilic diblock elastin polypeptide into core-shell nanoparticles. Elastin-mimetic protein polymers that comprise fusions of elastin sequences with different 7, values can be induced to undergo self-assembly at a temperature between the two transition temperatures, (b) Differential scanning calorimetry measurements indicate an endothermic transition for the more hydrophobic (lower 7 block with a value that corresponds to those observed for the burial of hydro-phobic residues within a folded protein, (c) This transition coincides with the formation of spherical assemblies in which the more hydrophobic block is confined within the micellar core. Transmission electron microscopy measurements are consistent with spherical micelles and more complex assemblies. Reprinted from Lee, T. A. T. Cooper, A. Apkarian, R. P. Conticello, V. P. Adv. Mater. 2000, f2(15), Copyright 2000, with... 

Amphiphilic Janus micelles were prepared using PSt-PBd-PMMA terpolymers synthesized by sequential anionic polymerization and cross-linking of the PBd spherical meso-phase in solid state. After solubilization and alkaline hydrolysis of PMMA to PMAA non-centrosymmetric compartmentalized micellar nanoparticles consisting of cross-linked PBd core and PSt, PMMA hemispheres were prepared and evaluated. ... 

Related to these structures and also of relevance for the preparation of nanoparticles are some amphiphile-based nanostructured phases which do not possess any long range order. For example, another type of bicontinuous phase with relation to the inverse bicontinous cubic phases is the so-called sponge phase (L3). Its curved bilayer structure is disordered so that the water channels adopt a sponge-like structure. Sometimes this phase is referred to as a "melted cubic (v2) phase". Moreover, also dispersions of inverse micellar phases (L2) have been described which may be regarded as "melted I2 phase". Although such disordered phases do not represent a liquid crystalline phase in a strict sense they are included here since they are of relevance for nanoparticulate drug delivery purposes. 

Figure 11.5. Nanosystems resulting from the self assembly of cetyl poly(ethylenimine) amphiphiles. The morphology of the resulting nanosystem depends on the level of hydrophobic substitution of the polymer backbone. With more hydrophilic polymers a high curvature micellar specie results, with intermediate hydrophobicity polymers, closed bilayer vesicles result and dense nanoparticles result when the level of hydrophobicity exceeds a critical value. The dense nanoparticles are in effect nanoprecipitates stabilised by a surface layer of the amphiphile. The size of the vesicular and dense nanoparticle assemblies are dependent on the level of cetylation of the amphiphiles. ...

An alternative strategy, which utilizes micelle-forming amphiphilic block copolymers in the stabilization of metal nanoparticles, has been extensively studied and can be described as nanoreactors as the metal colloids are synthesized within their interior. This has enabled the formation of nanosized (l-2nm) metal colliods or clusters within polystyrene-Z -polyvinylpyridine (PS- -PVP) micellar assemblies, with diameters around 30 mn, and these... 

Gianneschi and coworkers [74] demonstrated that peptides could also be polymerized via ROMP as the hydrophihc domain of an amphiphilic block copolymer in order to yield micellar nanoparticles of various sizes depending on the size and composition of each block. NBE-modified peptides were polymerized as the hydrophihc block, along with a phenyl NBE derivative to serve as the hydrophobic block of the amphiphile. The resulting polymers, termed peptide polymer amphiphUes (PPAs), formed spherical miceUes on the order of 20—SOOnm in diameter (Figure 6.18). 

In a similar manner, several nanoparticles have been produced in the presence of block copolymers in selective solvents so as to form micelles that encapsulate particles such as metal salts. Consequently, these micelles are chemically converted to finely disperse colloidal hybrid polymer/metal particles with interesting catalytic, non-linear optic, semiconductor and magnetic properties [1, 20]. Finally, another area of potential application of amphiphilic block copolymers is that involving surface modification through the adsorption of block copolymer micelles or film formation. The use of a suitable micellar system allows for the alteration of specific surface characteristics, such as wetting and biocompatibility, or even enables the dispersion and stabilisation of solid pigment particles in a liquid or solid phase [1, 178]. 

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