0000000000358708

AUTHOR

Gerhard Heuberger

showing 2 related works from this author

Size Dependence of Tracer Diffusion in Supercooled Liquids

1996

We have determined by forced Rayleigh scattering the diffusion coefficients D of several photochromic tracers with van der Waals radii between 0.38 and 8 nm (the largest ones being photolabeled polystyrene micronetworks) in 10 glass-forming liquids at temperatures between the glass temperature Tg and ∼1.2Tg. The results were analyzed in terms of power law plots, D(T) ∝ T/η(T)ξ, where η is the solvent shear viscosity, and temperature shifts, D(T) ∝ T/η(T + ΔT). The shift ΔT was related with the width of the rotational correlation time distribution via the time−temperature superposition principle.

ChemistryDiffusionGeneral EngineeringThermodynamicsPower lawPhysics::Fluid DynamicsCondensed Matter::Soft Condensed Mattersymbols.namesakeSuperposition principlechemistry.chemical_compoundsymbolsVan der Waals radiusPolystyrenePhysical and Theoretical ChemistrySupercoolingGlass transitionRotational correlation timeThe Journal of Physical Chemistry
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Probe diffusion in homogeneous diblock copolymers

1998

Forced Rayleigh scattering was used to investigate the diffusion of a photoreactive dye molecule in two homogeneous poly(styrene-b-isoprene) (SI) diblock copolymers with overall molecular weights of approximately 2000. Although diffusion rates were intermediate to TTI transport in homopolymer polystyrene (PS) and polyisoprene (PI), system dynamics appear to be largely dictated in each case by the PI block. The size of the polymer jumping unit, on the other hand, is evaluated from a free-volume analysis of the data, and is found to be governed predominantly by the PS component of the copolymer. The mechanism for tracer diffusion in low-molecular-weight block copolymers appears analogous to t…

chemistry.chemical_classificationMolecular diffusionPolymers and PlasticsChemistryDiffusionKineticsPolymerCondensed Matter PhysicsBlock (periodic table)Toluenechemistry.chemical_compoundChemical physicsPolymer chemistryMaterials ChemistryCopolymerPolystyrenePhysical and Theoretical ChemistryJournal of Polymer Science Part B: Polymer Physics
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