We present experiments and theory on the melt dynamics of monodisperse entangled polymers of comb-shaped architecture. Frequency-dependent rheological data on a series of comb polymers are in good agreement with a tube-model theory that combines star polymer melt behavior at high frequency with modified linear polymer reptation behavior at low frequencies. Taking into account mild polydispersity and by incorporating the high-frequency Rouse modes, we are able to model quantitatively the entire frequency range. Qualitatively distinct dynamical features of the comb architecture are compared to those of the simpler star and H-topologies.
The measurement of electrophoretic mobility is commonly done by laser Doppler electrophoresis (LDE).
Recently, a more sensitive technique, phase analysis light scattering (PALS), has been developed with
particular benefits for application to nonpolar systems. We have carried out PALS measurements of the
electrophoretic mobility (μ) of modified silica particles as a function of applied electric field. Our results
are in poor agreement with LDE measurements on the same system. We show that this difference might
result from the way in which PALS measurements are performed and suggest that, in this case, the known
field-dependent mobility will cause artifacts in the PALS data. When the mobility is field-dependent, this
factor must be accounted for appropriately in PALS data analysis.
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