Lateral diffusion of single poly(ethylene oxide) chains on the surfaces of glassy and molten polymer films

Matthew Mears, Zhenyu J. Zhang, Ryan C.D. Jackson, Yuchen Si, Tigerlily J.B. Bradford, John M. Torkelson, Mark Geoghegan

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Abstract

Fluorescence correlation spectroscopy was used to show that the temperature-dependent diffusion coefficient of poly(ethylene oxide) (PEO) adsorbed on polystyrene and different poly(alkyl methacrylate) (PAMA) films in aqueous solution exhibited a maximum close to (but below) the surface glass transition temperature, Tgs, of the film. This elevated diffusion was observed over a small range of temperatures below Tgs for these surfaces, and at other temperatures, the diffusion was similar to that on silicon, although the diffusion coefficient for PEO on polystyrene at temperatures above Tgs did not completely decrease to that on silicon, in contrast to the PAMA surfaces. It is concluded that the enhanced surface mobility of the films near the surface glass transition temperature induces conformational changes in the adsorbed PEO. The origin of this narrow and dramatic increase in diffusion coefficient is not clear, but it is proposed that it is caused by a coupling of a dominant capillary mode in the liquid surface layer with the polymer. Friction force microscopy experiments also demonstrate an unexpected increase in friction at the same temperature as the increase in diffusion coefficient.

Original languageEnglish
Article number164902
JournalJournal of Chemical Physics
Volume154
Issue number16
Early online date23 Apr 2021
DOIs
Publication statusPublished - 28 Apr 2021

Bibliographical note

Funding Information:
The EPSRC is acknowledged for providing financial support through a doctoral training award for MM and through Grant No. EP/I012060/1 for Z.J.Z. David Spiller at the University of Manchester is acknowledged for help with the FCS experiments of dextran presented in the supplementary material.

ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

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