Streamlined ellipsometry procedure for characterizing physical aging rates of thin polymer films

Elizabeth A. Baker, Perla Rittigstein, John M. Torkelson, Connie B. Roth

Research output: Contribution to journalArticle

42 Scopus citations

Abstract

Existing studies in the research literature showing conflicting changes in physical aging rates with decreasing film thickness in nanoconfined polymer films highlight the need for a single experimental technique to efficiently characterize physical aging rates in thin polymer films of varying chemical structure. To that end, we have developed a streamlined ellipsometry procedure to measure the structural relaxation of thin glassy polymer films. We evaluate different methods of calculating a physical aging rate β from the measured thickness h(t) and index of refraction n(t) data. We present extensive measurements of β as a function of aging temperature and aging time for polystyrene (PS) films supported on silicon, and determine that the physical aging rate β can be easily and reliably determined from β = -1/h o dh/ d(log t), where h o is the initial measure of the film thickness at an aging time of 10 min. We have also carried out oxygen permeation studies on poly(methyl methacrylate) (PMMA) films from 800 μm down to 190 nm in thickness, and find no change in the permeability with film thickness or physical aging at room temperature for up to 65 days, which suggests that gas permeation may be insensitive to physical aging in such low free volume polymers.

Original languageEnglish (US)
Pages (from-to)2509-2519
Number of pages11
JournalJournal of Polymer Science, Part B: Polymer Physics
Volume47
Issue number24
DOIs
StatePublished - Dec 15 2009

Keywords

  • Ellipsometry
  • Gas permeation
  • Glass transition
  • Physical aging
  • Poly(methyl methacrylate)
  • Polymer thin films
  • Polystyrene
  • Structural relaxation

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Physical and Theoretical Chemistry
  • Polymers and Plastics
  • Materials Chemistry

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