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  • 1
    Electronic Resource
    Electronic Resource
    Diffusion of labeled macromolecules in molten polystyrenes studied by a holographic grating technique (1984)
    s.l. : American Chemical Society
    Macromolecules 17 (1984), S. 798-802 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00134a046
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Dynamic light scattering study of concentrated microgel solutions as mesoscopic model of the glass transition in quasiatomic fluids (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 3950-3963 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: This paper presents a light scattering study of the dynamics of concentrated solutions of nearly monodisperse (σ≈0.16) spherical micronetwork particles consisting of highly cross-linked polystyrene dissolved in carbon disulfide, i.e., a "good'' solvent. Above volume fractions of cursive-phi=0.50 the intermediate scattering function, measured over a time window of 10−7 to 103 s using the ALV5000 correlator, decays in two steps and shows indications of nonergodic behavior for cursive-phi≥0.64. Such behavior is typical for glass forming systems and has recently been found close to the glass transition of a hard sphere colloidal system [W. van Megen and P. N. Pusey, Phys. Rev. A 43, 5429 (1991)]. Thus the introduced system can be used for modeling the glass transition of atoms on a mesoscopic scale. The traditional analysis of structural relaxation in terms of a Kohlrausch–Williams–Watts distribution yields a mean relaxation time which follows the empirical Mooney equation as a function of concentration and thus corresponds to Vogel–Fulcher–Tammann behavior. However, the necessity to add an unspecified "intermediate'' process between the short and long time KWW decays demonstrates the limitations of this "pragmatic'' approach. The mode coupling theory of the glass transition interprets the intermediate scattering function consistently over nearly seven decades in time, the intermediate region corresponding to the crossover from β to α relaxation (von Schweidler law). The critical volume fraction of 0.636 derived by this analysis corresponds to a value of 0.59 for an ideal monodisperse system which is well in accord with other experimental and computer simulation studies of the glass transition of atomic systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462934
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  • 3
    Electronic Resource
    Electronic Resource
    Experimental and theoretical investigation of the electrostatic persistence length of flexible polyelectrolytes at various ionic strengths (1992)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 96 (1992), S. 4008-4014 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100189a019
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Polymer topology and diffusion: a comparison of diffusion in linear and cyclic macromolecules (1992)
    s.l. : American Chemical Society
    Macromolecules 25 (1992), S. 3942-3947 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00041a017
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  • 5
    Electronic Resource
    Electronic Resource
    Synthesis of sponge-like polymer dispersions via polymerization of bicontinuous microemulsions (1996)
    Springer
    Colloid & polymer science 274 (1996), S. 696-702 
    Details
    ISSN: 1435-1536
    Keywords: Polymerization in bicontinuous microemulsions ; interaction of polymers with lyotropic phases ; sponge-like polymer dispersions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Polymer gels with high water content are made by polymerization of hydrophilic/hydrophobic monomer mixtures in bicontinuous microemulsions. These structures can be described as a heterophasic, bicontinuous polymer colloid-in-water structure, the characteristic length of which is only indirectly influenced by the original microemulsion mixture. The structure formation and phase changes throughout the polymerization reaction are followed with rheology, polarization microscopy, and scanning and transmission electron microscopy. It is shown that already the very first formed polymer changes disturb the bicontinuous phase structure and nucleate a vesicular phase; with further consumption of the monomer mixture, at least three other phase transitions can be detected, ending with a simple globular surfactant structure. Although direct templating of the original mesomorphous structure does not occur, the existence of the diverse lyotropic phases influences the final structure. It is shown that simple dilution changes the characteristic length of the network elements from about 2 μm down to 50 nm. This is explained by a combination of a nucleation-and-growth mechanism with the influence of a restricted colloidal stability in anisometric lyotropic phases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00653069
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  • 6
    Electronic Resource
    Electronic Resource
    Cobalt nanoparticles in block copolymer micelles: Preparation and properties (1997)
    Springer
    Colloid & polymer science 275 (1997), S. 426-431 
    Details
    ISSN: 1435-1536
    Keywords: Key words Cobalt nanoparticles ; block copolymer micelles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract  The preparation and properties of Co nanoparticles in polystyrene(PS)-poly-4-vinyl-py-ridine(PVP) micelles were studied. Elementary Co was generated by two methods: (i) by reduction of micelles loaded with CoCl2, and (ii) by thermal decomposition of Co2(CO)8 in micel-lar solutions of such block copolymers. Co particles formed by both processes are effectively stabilized by the block copolymer matrix and do not aggregate. For CoCl2 as a Co-source, the formed particles have a size less than 1 nm. Thermal treatment of such dried polymers at 200 °C for 2 h leads to spherical particles of 3–5 nm in size. The polymeric hybrid materials prepared in this way display remarkably high values of magnetization at rather low Co contents in the polymer, i.e., we obtain a tenfold increase of the specific magnetization density. Co2(CO)8 as a Co source, results in a more complex behavior. Co2(CO)8 dissolves in the solvent as well as in the micelle core where it is converted to an cationic–anionic complex involving the 4-VP units. The shape and size of the Co nanoparticles formed by thermolysis can be controlled by the balance of 4-VP/Co and can be varied from spherical particles in the limit of lower Co loads being mainly attached to the micelle core to a star-like and cubic morphology in case of excess of Co2(CO)8. Both superparamagnetic and ferromagnetic materials can be prepared. For ferromagnetic samples coercive force varies from 250 to 475 Oe depending on Co content and polymer sample.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003960050100
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  • 7
    Electronic Resource
    Electronic Resource
    Examination of the atypical electrophoretic mobility behavior of charged colloids in the low salt region using the O’Brian–White theory (1997)
    Springer
    Colloid & polymer science 275 (1997), S. 883-887 
    Details
    ISSN: 1435-1536
    Keywords: Key words Polystyrene latices ; electrophoretic mobility ; zeta potential
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract  Polystyrene microspheres having roughly the same size but different negative surface charge densities were prepared by emulsion polymerization. The amount of sulfate groups on the surface of the particles was controlled by variation of the amount and the decomposition rate of the initiator used, potassium, persulfate. After the cleaning process involving dialysis and extensive ultrafiltration the surface-charge density of the samples was determined and their electrokinetic behavior was studied. A simple model based on the Gouy–Chapman theory and the O’Brian–White approach allows the calculation of the dependence of the electrophoretic mobility on salt concentration. Comparison of the theoretical and experimental curves showed that they were in good agreement in a number of qualitative features. Moreover, the model revealed that a monotonously increasing zeta potential with falling electrolyte concentration results in a mobility maximum, and that this so-called atypical behavior is in accordance with the standard electrokinetic theory. No ion adsorption mechanism or the existence of a charged hairy layer, current standard explanations for this anomality, had to be invoked.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003960050161
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  • 8
    Electronic Resource
    Electronic Resource
    Equilibrium swelling of colloidal polymeric particles with water-insoluble organic solvents (2000)
    Springer
    Colloid & polymer science 278 (2000), S. 814-820 
    Details
    ISSN: 1435-1536
    Keywords: Key words Latex particles ; Swelling ; Interfacial tension ; Swelling pressure ; Size dependence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The Morton–Kaizerman–Altier (MKA) equation fails to describe experimental swelling data of polystyrene particles with toluene in the absence of free or adsorbed surfactants. A modification of the MKA equation is possible by the consideration of a volume work leading to a swelling pressure in analogy to macroscopic gels. With the modified equation a satisfactory description of the experimental data is possible if a size dependence of all the three interaction parameter of the particles with the swelling agent, the swelling pressure, and the interfacial tension of the particles is considered. In the case of particles with diameters below 50 nm and with high surface charge densities an additional electrostatic repulsion contributes to the volume increase during swelling, which is not yet considered in the theory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003960000318
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  • 9
    Electronic Resource
    Electronic Resource
    Iron oxyhydroxide colloids stabilized with polysaccharides (2000)
    Springer
    Colloid & polymer science 278 (2000), S. 491-501 
    Details
    ISSN: 1435-1536
    Keywords: Key words Self-assembled nanoreactor ; Nanoparticles ; Polysaccharides ; Colloid stabilization ; Iron oxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract  Neutralization of iron salts in aqueous solutions of κ-carrageenan and cellulose sulfate results in iron oxyhydroxide–polysaccharide hybrid colloids with unusual pH stability up to pH 13. It is shown that both polysaccharides form a tight polymer layer surrounding the inorganic particles, which in the case of κ-carrageenan is cross-linked by helical domains forming a self-assembled nanoreactor. The stabilized iron oxyhydroxide particles can undergo further reactions, for example, it is possible by a chemical reaction to produce stabilized magnetite particles. Repetition of the loading/neutralization steps in the reaction results in hybrids with iron contents much higher than the stoichiometric balance of iron and functional groups of the polymer (greater than 100% Fe/SO4 −). This combination of high iron content with a natural polysaccharide stabilizer makes these colloids interesting for a number of applications, for example, for nutritional purposes or as contrasting agents for tomography.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003960050546
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  • 10
    Electronic Resource
    Electronic Resource
    Synthesis and characterization of non-spherical gold colloids in block-copolymer micelles (1996)
    Springer
    Colloid & polymer science 274 (1996), S. 795-800 
    Details
    ISSN: 1435-1536
    Keywords: Noble metal colloid ; block-copolymers ; anisometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Gold colloids of well-defined shape, size and polydispersity are synthesized by heterogeneous reduction of gold salts in amphiphilic block-copolymer micelles. The resulting hybride systems consisting of the noble metal colloid and the stabilizing shell of block-copolymers are characterized by electron microscopy and small-angle x-ray scattering. Opposite to classical noble metal colloids, the block-copolymer stabilized systems exhibit an extra-ordinary high colloidal stability which makes analysis and sample handling very simple. It turned out that non-spherical metal colloids are formed in the early stages of the reduction process where the amount of gold exceeds the reduction agent. At later stages, the colloids break up to globular subunits again. The reaction period of colloidal anisometry is reflected in a violet color of the reaction solution, which is caused by a typical structured, double-resonance plasmon band. Small-and wide-angle x-ray scattering reveal a quantitative measure for the size, shape, anisometry and local order in each step of the reduction process. It is suggested that the primary aubergine-shaped particles consist of globular primary particles which are glued together via non reacted gold salt. This observation gives rise to some interesting possibilities of the supramolecular handling of colloids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00654676
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