"Experimental investigation of anomalous molecular probe diffusion in e" by D. Nieto Simavilla, V. Ramakrishnan et al.
 

Experimental investigation of anomalous molecular probe diffusion in entangled polymer melts

Document Type

Article

Publication Date

7-18-2022

Abstract

Investigations on the diffusion of small molecules or particles in polymeric materials are important to numerous technologies and can also be used to gain insight on polymer chain dynamics. Systems where the probe size is comparable to (or smaller than) a characteristic length of the polymer chain, the tube diameter for example, are of particular interest because the diffusion coefficient of the probe can be orders of magnitude larger than the value predicted by the Stokes-Einstein relation. In the present study, we employ the optical technique known as forced Rayleigh scattering to study the diffusion of a molecular probe (dye) in several entangled polymer melts over a wide range of length and time scales. The probe size is much smaller than the tube diameter for the systems studied. We find the diffusion coefficient is larger by four to five orders of magnitude than the Stokes-Einstein prediction. More interestingly, we observe anomalous, non-Fickian, diffusion where the value of the measured diffusion coefficient can abruptly change by as much as 50%. We suggest that this unexpected behavior occurs when the time scale for diffusion is larger than the relaxation time associated with the constraint release mechanism for polymer chain dynamics.

Identifier

85135337315 (Scopus)

Publication Title

Soft Matter

External Full Text Location

https://doi.org/10.1039/d2sm00759b

e-ISSN

17446848

ISSN

1744683X

PubMed ID

35876110

First Page

6200

Last Page

6208

Issue

33

Volume

18

Grant

36659-AC9

Fund Ref

American Chemical Society Petroleum Research Fund

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