Non-Aqueous Synthesis of CeO<SUB>2</SUB> Nanoparticles Using Block Copolymer Micelles as Templates and Their Assembly Into Porous Structures with Enhanced Catalytic Activity

When two electrolyte solutions are separated and only some of the ions can cross the boundary, the concentrations of these ions are different on both sides of the boundary. This is the well-known Donnan effect. When weak electrolytes are involved, the imbalance includes also hydrogen ions: there is a difference of pH across the boundary and the dissociation of nondiffusible weak electrolytes is suppressed. The effect is very pronounced when the concentration of the weak electrolyte is high and ionic strength is low. The significance of this phenomenon is discussed for polyelectrolyte solutions, and particularly for block copolymer micelles with weak polyelectrolyte shells. The effect is quite dramatic in the latter case.

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A Monte Carlo Study of Flexible Polymer Chain Conformations in Restricted Volumes. I. A Model for Insoluble Blocks Conformations in Swollen Cores of Multimolecular Spherical Block Copolymer Micelles

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19932290 ◽

1993 ◽

Vol 58 (10) ◽

pp. 2290-2304 ◽

Cited By ~ 2

Author(s):

Zuzana Limpouchová ◽

Karel Procházka

Keyword(s):

Monte Carlo ◽

Block Copolymer ◽

Monte Carlo Study ◽

Volume Effect ◽

Micellar Systems ◽

Flexible Polymer ◽

Block Copolymer Micelles ◽

Copolymer Micelles ◽

Chain Conformations ◽

Chain Lengths

Monte Carlo simulations of chain conformations in a restricted spherical volume at relatively high densities of segments were performed for various numbers of chains, N, and chain lengths (number of segments), L, on a tetrahedral lattice. All chains are randomly end-tethered to the surface of the sphere. A relatively uniform surface density of the tethered ends is guaranteed in our simulations. A simultaneous self-avoiding walk of all chains creates starting conformations for a subsequent equilibration. A modified algorithm similar to that of Siepmann and Frenkel is used for the equilibration of the chain conformations. In this paper, only a geometrical excluded volume effect of segments is considered. Various structural and conformational characteristics, e.g. segment densities gS(r), free end densities gF(r) as functions of the position in the sphere (a distance from the center), distributions of the tethered-to-free end distances, ρTF(rTF), etc. are calculated and their physical meaning is discussed. The model is suitable for studies of chain conformations is swollen cores of multimolecular block copolymer micelles and for interpretation of non-radiative excitation energy migration in polymeric micellar systems.

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Study of Sedimentation Velocity of Block Copolymer Micelles

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19930071 ◽

1993 ◽

Vol 58 (1) ◽

pp. 71-76 ◽

Cited By ~ 3

Author(s):

Minmin Tian ◽

C. Ramireddy ◽

Stephen E. Webber ◽

Petr Munk

Keyword(s):

Block Copolymer ◽

Methacrylic Acid ◽

Mixed Solvent ◽

Hard Spheres ◽

Sedimentation Velocity ◽

Hydrodynamic Coefficient ◽

Block Copolymer Micelles ◽

Copolymer Micelles ◽

Size Heterogeneity ◽

Good Agreement

No anomalies were observed during the measurement of sedimentation coefficients of block copolymer micelles formed by copolymers of styrene and methacrylic acid in a mixed solvent; 80 vol.% of dioxane and 20 vol.% of water. The shapes of the sedimenting boundaries suggest that the size heterogeneity of the micelles is small. Linear relations between 1/s and c were obtained. The value of the hydrodynamic coefficient κ was between 2 and 4 in a good agreement with the value 2.75 or 2.86 that was obtained by combining Burgers' or Fixman's values of the coefficient of the concentration dependence kvs for hard spheres with Einstein's value of [η] for spheres.

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