Abstract
Understanding the dynamics of soft colloids, such as star polymers, dendrimers, and microgels, is of scientific and practical importance. It is known that the excluded volume effect plays a key role in colloidal dynamics. Here, we propose a condition of compressibility equivalence that provides a simple method to experimentally evaluate the excluded volume of soft colloids from a thermodynamic view. We apply this condition to survey the dynamics of a series of star polymer dispersions. It is found that, as the concentration increases, the slowing of the long-time self-diffusivity of the star polymer, normalized by the short-time self-diffusivity, can be mapped onto the hard-sphere behavior. This phenomenon reveals the dynamic equivalence between soft colloids and hard spheres, despite the apparent complexity of the interparticle interaction of the soft colloids. The methods for measuring the osmotic compressibility and the self-diffusivities of soft colloidal dispersions are also presented.
Original language | English |
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Pages (from-to) | 1467-1473 |
Number of pages | 7 |
Journal | ACS Macro Letters |
DOIs | |
State | Published - 2019 |
Funding
We are grateful to Dr. J. F. Douglas for valuable discussion. We acknowledge the support of NIST Center for Neutron Research, Spallation Neutron Source at Oak Ridge National Laboratory, and Institut Laue-Langevin, in providing the neutron research facilities, and the NMR facility at the University of Arizona in performing the NMR measurements. Access to Neutron Spin Echo and SANS at NIST was provided by the Center for High Resolution Neutron Scattering, a partnership between the National Institute of Standards and Technology and the National Science Foundation under Agreement No. DMR-1508249. This research at SNS of Oak Ridge National Laboratory was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy. The research at Tsinghua University was supported by the Starting Grant from Tsinghua University.