Tim Mortensen - Academia.edu (original) (raw)
Related Authors
University of the Basque Country, Euskal Herriko Unibertsitatea
Uploads
Papers by Tim Mortensen
Physical Review E, 2005
Self-intermediate scattering functions ͑ISFs͒ are measured by dynamic light scattering for the co... more Self-intermediate scattering functions ͑ISFs͒ are measured by dynamic light scattering for the colloidal fluid of hard spheres for both equilibrium and nonequilibrium ͑undercooled͒ conditions, i.e., for volume fractions below and above the known freezing transition of the hard-sphere system. The delay time m where the mean-squared displacement, or the low wave-vector limit of the ISF, exhibits its maximum stretching is identified as a characteristic of the non-Markovian process͑es͒ and is used to separate the ISF into fast ͑ Ͻ m ͒ and slow ͑ Ͼ m ͒ contributions. Each of these contributions exposes qualitative differences in the dynamics of the particles between the equilibrium and nonequilibrium colloidal fluids. These changes in the relaxation scenario signal the colloidal fluid's awareness of its traversal of the freezing volume fraction.
Journal of Colloid and Interface Science, 1999
We analyze the core-shell structure of sterically stabilized hard sphere polymer colloids by opti... more We analyze the core-shell structure of sterically stabilized hard sphere polymer colloids by optical contrast variation. Modified polymer particles are used which have the same refractive index as the suspending solvent. At low contrast, inhomogeneities in the coreshell structure of the particles become apparent. The particle form factor is shown to be a sensitive function of the temperature due to the interplay of scattering from the core and the stabilizing layer. We explore the dependence of particle form factors on composition, radius, and temperature and rationalize our observations in terms of a simple core-shell model. By exploiting the sensitivity of the form factors we are able to independently study the two components of a binary mixture of polymer particles.
Physical Review E, 2005
Self-intermediate scattering functions ͑ISFs͒ are measured by dynamic light scattering for the co... more Self-intermediate scattering functions ͑ISFs͒ are measured by dynamic light scattering for the colloidal fluid of hard spheres for both equilibrium and nonequilibrium ͑undercooled͒ conditions, i.e., for volume fractions below and above the known freezing transition of the hard-sphere system. The delay time m where the mean-squared displacement, or the low wave-vector limit of the ISF, exhibits its maximum stretching is identified as a characteristic of the non-Markovian process͑es͒ and is used to separate the ISF into fast ͑ Ͻ m ͒ and slow ͑ Ͼ m ͒ contributions. Each of these contributions exposes qualitative differences in the dynamics of the particles between the equilibrium and nonequilibrium colloidal fluids. These changes in the relaxation scenario signal the colloidal fluid's awareness of its traversal of the freezing volume fraction.
Journal of Colloid and Interface Science, 1999
We analyze the core-shell structure of sterically stabilized hard sphere polymer colloids by opti... more We analyze the core-shell structure of sterically stabilized hard sphere polymer colloids by optical contrast variation. Modified polymer particles are used which have the same refractive index as the suspending solvent. At low contrast, inhomogeneities in the coreshell structure of the particles become apparent. The particle form factor is shown to be a sensitive function of the temperature due to the interplay of scattering from the core and the stabilizing layer. We explore the dependence of particle form factors on composition, radius, and temperature and rationalize our observations in terms of a simple core-shell model. By exploiting the sensitivity of the form factors we are able to independently study the two components of a binary mixture of polymer particles.