Effect of surface-influenced order on thermal expansivity of polymer thin films

C. Thompson, R. F. Saraf, J. L. Jordan-Sweet

Research output: Contribution to journalArticlepeer-review

10 Scopus citations


Variations of the thermal expansion coefficient of thin polyimide films as a function of film thickness (40-260 nm) have been measured by monitoring film thickness as a function of temperature using X-ray reflectivity from samples of poly(pyromellitic dianhydride oxydianiline) (PMDA-ODA) films spin-cast onto silicon wafers. The effective expansion coefficient of the film decreases with decreasing thickness and is consistent with a bilayer model in which an interfacial region of constant thickness is formed for each film. The expansion coefficient of this surface or interfacial region is less than one-third the coefficient of the interior of the films. A simple method is described whereby the thermal expansion coefficient may be determined by reflectivity.

Original languageEnglish (US)
Pages (from-to)7135-7140
Number of pages6
Issue number26
StatePublished - Dec 24 1997
Externally publishedYes

ASJC Scopus subject areas

  • General Materials Science
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Spectroscopy
  • Electrochemistry


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