Molecular probe techniques for studying diffusion and relaxation in thin and ultrathin polymer films

David B. Hall, R. D. Miller, John M Torkelson*

*Corresponding author for this work

Research output: Contribution to journalArticle

37 Scopus citations

Abstract

Two optically based, molecular probe techniques are employed to study relaxation and small-molecule translational diffusion in thin and ultrathin (thicknesses < ∼200 nm) polymer films. Second harmonic generation (SHG) is used to study the reorientational dynamics of a nonlinear optical chromophore, Disperse Red 1 (DR1) (previously shown to be an effective probe of α-relaxation dynamics) either covalently attached or freely doped in polymer films. Our studies on films ranging in thickness from 7 nm to 1 μm show little change in Tg with film thickness; however, a substantial broadening of the relaxation distribution is observed as film thickness decreases below approximately 150 nm. Experimental guidelines are given for using fluorescence nonradiative energy transfer (NRET) to study translational diffusion in ultrathin polymer films. Appropriate choice of a fluorescence donor species is important along with ensuring that diffusion is slow enough to be measured appropriately. Initial results on the diffusion of a small-molecule probe, lophine, in poly(isobutyl methacrylate) indicates that there is little change in probe diffusion coefficients in films as thin as 90 nm as compared to bulk films.

Original languageEnglish (US)
Pages (from-to)2795-2802
Number of pages8
JournalJournal of Polymer Science, Part B: Polymer Physics
Volume35
Issue number17
DOIs
StatePublished - Jan 1 1997

Keywords

  • Fluorescence nonradiative energy transfer
  • Polymer relaxation
  • Second harmonic generation
  • Small-molecule diffusion
  • Ultrathin polymer films

ASJC Scopus subject areas

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

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