Monodisperse preparation

VII According to Husain and Sadana (4S3), the earlier preparation of Achromobacter fischeri nitrite reductase with a molecular weight of 95,000 40,000 341) was found to be polydisperse. A monodisperse preparation subsequently studied (433) had a molecular weight of 80,000, and was shown to be composed of two subunits of approximate molecular weights of 39,000 with methionine as the sole N-terminal residue. The subunits are stated to be linked together by disulfide bridges. 

Even when carefully prepared, model colloids are almost never perfectly monodisperse. The spread in particle sizes, or polydispersity, is usually expressed as the relative widtli of tire size distribution,... 

An important step in tire progress of colloid science was tire development of monodisperse polymer latex suspensions in tire 1950s. These are prepared by emulsion polymerization, which is nowadays also carried out industrially on a large scale for many different polymers. Perhaps tire best-studied colloidal model system is tliat of polystyrene (PS) latex [9]. This is prepared with a hydrophilic group (such as sulphate) at tire end of each molecule. In water tliis produces well defined spheres witli a number of end groups at tire surface, which (partly) ionize to... 

One model for rod-like colloids is tire tobacco mosaic vims (TM V), which consists of rods of diameter D about 18 nm and lengtli L of 300 nm [17,18]. These colloids have tire advantage of being quite monodisperse, but are hard to obtain in large amounts. The fd vims gives longer, semi-flexible rods (L = 880 nm, D = 9 nm) [18,19]. Inorganic boehmite rods have also been prepared successfully [20]. 

Matijevi i E 1976 Preparation and oharaoterization of monodispersed metal hydrous oxide sols Prog. Colloid Polym. Sol. 61 24-35... 

Pathmamanoharan C and Philipse A P 1998 Preparation and properties of monodisperse magnetic cobalt colloids grafted with polyisobutene J. Colloid Interface Sol. 205 304-53... 

Figure C2.17.3. Close-packed array of sub-micrometre silica nanoparticles. Wlren nanoparticles are very monodisperse, they will spontaneously arrange into hexagonal close-packed stmcture. This scanning electron micrograph shows an example of this for very monodisperse silica nanoparticles of -250 nm diameter, prepared in a thin-film fonnat following the teclmiques outlined in [236].

Monodispersed poly (methyl methacrylate-ethyleneglycol dimethacrylate) is prepared by a multistep swelling and polymerization method. When a good solvent such as toluene is applied as a porogen, the seed polymer severely affects the pore structure, whereas no effects are observed with poor solvents, such as cyclohexanol, as a porogen, in comparison with the conventional suspension polymerization (68,69). 

Soapless seeded emulsion copolymerization has been proposed as an alternative method for the preparation of uniform copolymer microspheres in the submicron-size range [115-117]. In this process, a small part of the total monomer-comonomer mixture is added into the water phase to start the copolymerization with a lower monomer phase-water ratio relative to the conventional direct process to prevent the coagulation and monodispersity defects. The functional comonomer concentration in the monomer-comonomer mixture is also kept below 10% (by mole). The water phase including the initiator is kept at the polymerization temperature during and after the addition of initial monomer mixture. The nucleation takes place by the precipitation of copolymer macromolecules, and initially formed copolymer nuclei collide and form larger particles. After particle formation with the initial lower organic phase-water ratio, an oligomer initiated in the continuous phase is... 

Dendrimers have structures similar to that of hyperbranched polymer and can be taken as the perfectly branched polymer with monodispersity. However, they need to be prepared by a multistep procedure. Therefore, very little work has been done on dendritic polyfarylcnc ether)s. Morikawa et al. prepared a series of monomers with a various number of phenylene units.164,165 These monomer were used to prepare poly(ether ketone) dendrons with graded structures (Scheme 6.24). 

Sometimes it can be advantageous to use mixtures of alkanesulfonates and nonionic surfactants, such as Triton X-100, to prepare monodisperse polystyrene particles [95]. 

Monodisperse polymers for this purpose may be obtained from commercial suppliers, but they are expensive and for many polymers not available in sufficiently narrow molar mass fractions. For this reason, the not very satisfactory procedure is sometimes adopted of calibration with polystyrene, since this polymer can be relatively easily prepared in discrete, monodisperse fractions using anionic polymerisation. The unknown polymer is then... 

The sequential growth and branching involved in the preparation of dendrimers had been considered by Flory many years before they were actually prepared. Flory developed a sound understanding of the kind of processes that would occur in the self-polymerization of a molecule of the type ABj most of which have been shown to be correct by the relatively recent experimental studies. In particular, the existence of a limit to growth was predicted. This limit has become known as the starburst limit, and is the reason for the highly monodisperse nature of fully developed dendrimers. 

Schmitt V, Leal-Calderon F, Bibette J (2003) Preparation of Monodisperse Particles and Emulsions by Controlled Shear. 227 195-215... 

Torchilin, V. P. (2006). Multifunctional nanocarriers. Advanced Drug Delivery Reviews, Vol. 58, 14, (December 2006), pp. (1532-1555), ISSN 0169-409X Tran, V. T., Benoit, J. P. Venier-Julienne, M. C. (2011). Why and how to prepare biodegradable, monodispersed, polymeric microparticles in the field of pharmacy International Journal of Pharmaceutics, Vol. 407,1-2, (December 2011), pp. (1-11), ISSN 0378-5173... 

Among all semiconductor NPs, metal selenides have been the focus of great attention due to their importance in various applications such as thermoelectric cooling materials, optical filters and sensors, optical recording materials, solar cells, superionic materials, laser materials and biological labels. Many synthetic methods have been developed for the preparation of relatively monodispersed selenide nanopartides (Murray et al., 1993 Korgel... 

For example, the parameters g = 0.77, h = 0.94, p = 1.4, and C = 0.158 measured for a polymer sample and compared with the plots in Figures 7.11 through 7.13 were most consistent with athree-arm star monodisperse polymer a poly disperse three-arm star would have g= 1.12,/ = 1.05,p= 1.6, and C close to 0.2. °° The second example was poly(vinyl acetate) (PVAc) prepared by emulsion polymerization. Since no data for linear equivalent were available, g and h were not calculated. At lower conversion/MW p= 1.84 was found, only slightly higher than the theoretically expected p = 1.73 for a randomly branched architecture, p slightly decreased with increasing M, indicating... 

Schluter AD (2005) A Covalent Chemistry Approach to Giant Macromolecules with Cylindrical Shape and an Engineerable Interior and Surface. 245 151-191 Schmitt V, Leal-Calderon F, Bibette J (2003) Preparation of Monodisperse Particles and Emulsions by Controlled Shear. 227 195-215... 

Preparation of monodisperse vesicles with variable size by dilution of mixed micellar solutions of bile salt and phosphatidylcholine, Biochim. Biophys. Acta, 775. 111-114. 

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