Micelle size

The observation of slow, confined water motion in AOT reverse micelles is also supported by measured dielectric relaxation of the water pool. Using terahertz time-domain spectroscopy, the dielectric properties of water in the reverse micelles have been investigated by Mittleman et al. [36]. They found that both the time scale and amplitude of the relaxation was smaller than those of bulk water. They attributed these results to the reduction of long-range collective motion due to the confinement of the water in the nanometer-sized micelles. These results suggested that free water motion in the reverse micelles are not equivalent to bulk solvation dynamics. 

When casein micelles are dissociated, spherical particles are observed with a size similar to the scale of the substructure. Moreover, the number of spherical particles formed by dissociation appears to correspond roughly to the number of substructural elements in the micelle. In electron micrographs of mammary gland secretory cells, some of the Golgi vesicles contain particles of a size similar to that of the particles formed by dissociation of micelles, whereas others contain larger particles. Buchheim and Welsch (1973) proposed that the smaller particles are not small micelles but subunits that are to be assembled into full-sized micelles. The envisaged sequence of assembly is as follows ... 

Aggregation number Radius of gyration, RG Hydrodynamic radius, RH Core/corona size, micelle structure, overall micelle size... 

In this system the average particle size depends on the BH4 Ni " ratio, the nickel salt concentration and the size of the inner water core of the reversed micelle. A BH4" Ni ratio of three gives the smallest size catalyst particles. Lower ratios lead to the formation of larger particles while higher ratios have no further effect on particle size. Micelles with smaller water cores produce smaller catalyst particles. The effect of nickel salt concentration on particle size is complex the smallest particles are formed with a concentration of 5x10"2M. Fig. 12.3 shows the relationship between the micelle composition, nickel salt concentration and the nickel boride particle size. For any given preparation the catalyst particles are essentially uniformly sized with only a 0.5 run distribution. ... 

N(r) can be related to the fractal dimension D of the protein-surfactant complex by the equation N r) = (r/R jP. For a freely diffusing micelle the fractal dimension would be 3, but in a complex the distribution of micelles is dictated by the topology of the polypeptide backbone, so that the fractal dimension is less than 3. At 1% by weight of lithium n-dodecylsulphate, D is 2.3 and decreases to 1.76 at 3%, consistent with a transition from a compact state to a more open random coil in which a string of constant-sized micelles are distributed along the hydrophobic patches of a denatured random coil, although the coil will be restrained by the 17 disulphide bonds in the BSA structure. 

Because of their size, micelles diffuse only slowly. According to the Stokes-Einstein relation the diffusion constant D of spherical objects of radius r in a medium of viscosity t) is given by... 

Increasing costs of radioactive waste and solvents have made it necessary to apply new approaches in LSC sample preparation. New liquid scintillators are capable of incubating twice as much or even more of aqueous samples than the classical colloidal scintillator systems with a stable and smaller and uniform size micelle formation and without formation of viscous liquid crystals. Counting efficiency remains at the same level as before when using small vials fitting inside of the standard classical ones. 

Surfactants other than SDS, which have different CMCs and form different size micelles with different interior polarity, can be used. If a cationic surfactant such as cetyltrimethylammonium bromide is used, the direction of the EOF will be reversed by the formation of a capillary surface... 

Multiscale surface structures have been directly obtained by simple spin-coating from diblock copolymer/homopolymer blends. For instance. Park et al. [89] prepared films from PS-b-P2VP/PMMA blends. These films were prepared from a selective solvent either for PS or PMMA. The pure block copolymers (BCP) form nanometer-sized micelles as a consequence of the microphase separation due to the incompatibility between the constituent blocks (Fig. 6.13(a)). However, blending the BCP with a homopolymer induces macrophase separation between the BCP micelles and the PMMA and the formation of isolated PMMA micrometer-size domains (Fig. 6.13(b)-(e)). Other groups including Jeong et al. [50] or Ibarboure et al. [42] also used homopolymer/BCP blends to fabricate multiscale ordered surfaces. Jeong and coworkers used P(S-b-MMA)/PMMA blends with variable composition. 

Micellar solutions and microemulsions are also used for parenteral delivery of hydrophobic drugs. They are usually stabilized by large amounts of hydrophilic surfactants, such as bile salts and polysorbates. Owing to their small size, micelles are less readily recognized by the immune system, resulting in prolonged circulation [36]. An example of micellar formulation is Taxol , in which the active antitumor agent paclitaxel is solubilized in micelles of polyoxyl castor oil. 

Consider a population of spherical nano-size micelles with a stable aggregation number A in a solution which also contains water and individual amphiphilic molecules (monomers). The Gibbs energy (per molecule) of the solution is... 

In vivo studies showed that the free radiolabelled compound remained in the blood at moderate levels after 3 hours and there was low liver accumulation. Contrary to expectation, the smaller size micelles of PLA-PEG copolymers did accumulate in the liver. It was necessary to have micelles with size >100 nm to evade phagocytosis. By optimising the size of the micelles and controlling the surface characteristics, it is possible to produce nano-particles that can be applied as drug carriers. 

Methoxy poly(ethylene glycol)-b-poly(caprolactone) copolymers Nano-sized micelles Drug delivery in blood/plasma Increase of drug kinetic... 

Owing to their lipophilic chains and their very small size, micelles are very easily dispersed in base oils and dispersion is stable for a long time. Overbased micelles, used initially as detergents, also present antiwear properties (see Chapter 4). Overbased micelles can be used in several ways (a) as thin coatings deposited on a solid surface, (b) as a colloidal dispersion in apolar medium (oil, grease, etc.) and (c) in gas phase lubrication. 

Multiscale patterns having micro and nanostructures can be obtained by simple evaporation using spin-coating from diblock copolymers/homopolymers or pure homopolymer blends. Park et al. prepared [206] films from PS- -P2VP/PMMA blends were prepared from a selective solvent either for PS or PMMA. The BC form nanometer-sized micelles by microphase separation as a consequence of the incompatibility between the constituent blocks. Moreover, blending the BC with a homopolymer... 

In this present woik, the formation of nano-size micelles base on triblock copolymer has been successfully prepared. The micelles did not affect the cell viability at concentration up to 1.0 mg/mL. The DOX release profile was a pH dependent maimer and the higher release rate was observed at acidic condition. Additionally, the micelles did not induce NO production and hemolytic levels compared with control group. A combination of NO production and cytotoxicity of the micelle suggested that the copolymeric micelle in this study had an extremely low toxicity and was safe for intravenous injection. 

Hsieh M.F, Cuong N.V et al. (2008) Nano-Sized Micelles of Block Copolymers of Methoxy Poly(ethylene glycol)-Poly(E-caprolactone)-Graft-2-Hydroxyethyl Cellulose for Doxorubicin Delivery. J. Nanosci. Nanotechnol 8 2362-2368. 

In this study, biodegradable amphiphilic PCL-PEG-PCL copolymer was synthesized. In aqueous medium, this amphiphilic copolymer can form nano-sized micelles. The properties of nanoparticles as drag carriers were investigated, including CMC values and particle size. Moreover, the biocompatibility of polymeric nanopaiticles was also evaluated in vitro. The cytotoxicity was examined in L929 mouse fibroblasts cell line. Furthermore, nitric oxide (NO) production and reactive oxygen species (ROS> generation were also demonstrated. 

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