The European Physical Journal E

, Volume 19, Issue 4, pp 423–432 | Cite as

Spinodal wrinkling in thin-film poly(ethylene oxide)/polystyrene bilayers

  • J. S. Sharp
  • D. Vader
  • J. A. Forrest
  • M. I. Smith
  • M. Khomenko
  • K. Dalnoki-Veress
Regular Article

Abstract.

Optical microscopy and atomic force microscopy were used to study a novel roughness-induced wrinkling instability in thin-film bilayers of poly(ethylene oxide) (PEO) and polystyrene (PS). The observed wrinkling morphology is manifested as a periodic undulation at the surface of the samples and occurs when the bilayers are heated above the melting temperature of the semi crystalline PEO (Tm = 63 \(\ensuremath ^{\circ}{\rm C}\)) layer. During the wrinkling of the glassy PS capping layers the system selects a characteristic wavelength that has the largest amplitude growth rate. This initial wavelength is shown to increase monotonically with increasing thickness of the PEO layer. We also show that for a given PEO film thickness, the wavelength can be varied independently by changing the thickness of the PS capping layers. A model based upon a simple linear stability analysis was developed to analyse the data collected for the PS and PEO film thickness dependences of the fastest growing wavelength in the system. The predictions of this theory are that the strain induced in the PS layer caused by changes in the area of the PEO/PS interface during the melting of the PEO are sufficient to drive the wrinkling instability. A consideration of the mechanical response of the PEO and PS layers to the deformations caused by wrinkling then allows us to use this simple theory to predict the fastest growing wavelength in the system.

PACS.

68.55.-a Thin film structure and morphology 61.41.+e Polymers, elastomers, and plastics 68.35.Ct Interface structure and roughness 68.35.Ja Surface and interface dynamics and vibrations 

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Copyright information

© EDP Sciences, Società Italiana di Fisica and Springer-Verlag 2006

Authors and Affiliations

  • J. S. Sharp
    • 1
  • D. Vader
    • 2
    • 3
  • J. A. Forrest
    • 2
  • M. I. Smith
    • 1
  • M. Khomenko
    • 2
  • K. Dalnoki-Veress
    • 4
  1. 1.School of Physics and AstronomyUniversity of NottinghamNottinghamUK
  2. 2.Department of Physics and Guelph-Waterloo Physics InstituteUniversity of WaterlooWaterlooCanada
  3. 3.Division of Engineering and Applied SciencesHarvard UniversityCambridgeUSA
  4. 4.Department of Physics and AstronomyMcMaster UniversityHamiltonCanada

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