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A Multitechnique Study of Structure and Dynamics of Polyfluorene Cast Films and the Influence on Their Photoluminescence

På svenska

Author

  • Gregorio C. Faria
  • Tomás Plivelic
  • Rafael F. Cossiello
  • André A. Souza
  • Tereza D. Z. Atvars
  • Iris L. Torriani
  • Eduardo R. deAzevedo

Summary, in English

This article describes the microstructure and dynamics in the solid state of polyfluorene-based polymers, poly(9,9-dioctylfluorenyl-2,7-diyl) (PFO), a semicrystalline polymer, and poly[(9,9-dioctyl-2,7-divinylene-fluorenylene)-alt-co-{2-methoxy-5-(2-ethyl-hexyloxy)-1,4-phenylene vinylene}, a copolymer with mesomorphic phase properties. These structures were determined by wide-angle X-ray scattering (WAXS) measurements. Assuming a packing model for the copolymer structure, where the planes of the phenyl rings are stacked and separated by an average distance of 4.5 Å and laterally spaced by about 16 Å, we followed the evolution of these distances as a function of temperature using WAXS and associated the changes observed to the polymer relaxation processes identified by dynamical mechanical thermal analysis. Specific molecular motions were studied by solid-state nuclear magnetic resonance. The onset of the side-chain motion at about 213 K (β-relaxation) produced a small increase in the lateral spacing and in the stacking distance of the phenyl rings in the aggregated structures. Besides, at about 383 K (α-relaxation) there occurs a significant increase in the amplitude of the torsion motion in the backbone, producing a greater increase in the stacking distance of the phenyl rings. Similar results were observed in the semicrystalline phase of PFO, but in this case the presence of the crystalline structure affects considerably the overall dynamics, which tends to be more hindered. Put together, our data explain many features of the temperature dependence of the photoluminescence of these two polymers.

Department/s

Publishing year

2009

Language

English

Pages

11403-11413

Publication/Series

The Journal of Physical Chemistry Part B

Volume

113

Issue

33

Document type

Journal article

Publisher

The American Chemical Society (ACS)

Topic

  • Physical Sciences
  • Natural Sciences

Keywords

  • NMR
  • WAXS
  • molecular dynamics
  • supramolecular structure
  • electroluminescent polymer

Status

Published

ISBN/ISSN/Other

  • ISSN: 1520-5207