Coupling Analysis of Probe Diffusion in High Molecular Weight Hydroxypropylcellulose

Document Type

Article

Publication Date

3-2-1999

Publication Title

Journal of Physical Chemistry B

Abstract

The coupling/scaling model of Ngai and Phillies [Ngai, K. L., Phillies, G. D. J. J. Chem. Phys. 1996, 105, 8385] is applied to light scattering spectra of mesoscopic probes in 1 MDa hydroxypropylcellulose (HPC): water. Spectra are bimodal. The coupling/scaling model works for one mode but not the other. Probes smaller than the hydrodynamic radius of the HPC show a two-stretched-exponential relaxation: The slow mode follows coupling/scaling predictions; the fast mode does not. Probes whose diameters are comparable to or larger than the radius of gyration have spectra composed of a fast, stretched-exponential mode that follows coupling/scaling, and a slow, pure-exponential mode not described by coupling/scaling. Interpretations of the success or failure of the coupling/scaling model for various modes and probes are advanced, based on relationships between the observed and assumed spectral line shapes, and on the absolute time scale of each relaxation.

Comments

The partial support of this work by the National Science Foundation under Grant DMR94-23702 is gratefully acknowledged.

DOI

10.1021/jp982804v

Volume

103

Issue

11

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