Fluorescence studies of confinement in polymer films and nanocomposites: Glass transition temperature, plasticizer effects, and sensitivity to stress relaxation and local polarity

M. K. Mundra*, C. J. Ellison, P. Rittigstein, J. M. Torkelson

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

69 Scopus citations

Abstract

Confinement effects in polystyrene and poly(methylmethacrylate) films and nanocomposites are studied by fluorescence. The ability to employ an intensive measurable, the excited-state fluorescence lifetime, in defining the glass transition temperature, Tg, of polymers is demonstrated and compared to the use of an extensive measurable, fluorescence intensity. In addition, intrinsic fluorescence from the phenyl groups in polystyrene is used to determine the Tg-confinement effect in films as thin as ∼15 nm. The decrease in Tg with decreasing film thickness (below ∼60 nm) agrees well with results obtained by extrinsicpyrene fluorescence. Dye label fluorescence is used to quantify theenhancement in Tg observed with decreasing thickness (below ∼90 nm) in poly(methyl methacrylate) films; addition of 2-4 wt% dioctyl phthalate plasticizer reduces or eliminates the Tg-confinement effect in films down to 20 nm thickness. Intrinsic polystyrene fluorescence, which is sensitive to local conformation, is used to quantify the time scales (some tens of minutes) associated with stress relaxation in thin and ultrathinspin-coated films at Tg + 10 K. Finally, the shape of the fluorescence spectrum of pyrene doped at trace levels in polystyrene films and polystyrene-silica nanocomposites is used to determine effects of confinement on microenvironment polarity.

Original languageEnglish (US)
Pages (from-to)143-151
Number of pages9
JournalEuropean Physical Journal: Special Topics
Volume141
Issue number1
DOIs
StatePublished - Feb 1 2007

ASJC Scopus subject areas

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

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