Size-dependent mechanical behavior of free-standing glassy polymer thin films

Wenjie Xia, Sinan Keten*

*Corresponding author for this work

Research output: Contribution to journalArticle

18 Scopus citations

Abstract

The mechanical properties of nanoscale free-standing polymer thin films exhibit size dependence due to surface effects. However, it remains a challenge to determine the length scales at which differences are exhibited between film and bulk polymer properties. Here we use molecular dynamics simulations to uncover the dependence of elastic modulus (E) of free-standing films on film thickness and bulk properties. Comparison of the glass transition temperature (Tg) and E indicates that Tg converges to the bulk value slightly faster as the film thickness increases. The free-surface effects that give rise to a depression in E and Tg are observed to be stronger for polymers with weaker intermolecular interactions. The most intriguing aspect of our study is the finding that despite the observed decrease in the modulus of the film up to a thickness of over 100 nm, the local stress distribution reveals that the preserved length scale of perturbation of the free surface is only several nanometers.

Original languageEnglish (US)
Pages (from-to)36-45
Number of pages10
JournalJournal of Materials Research
Volume30
Issue number1
DOIs
StatePublished - Sep 23 2014

Keywords

  • Elastic properties
  • Film
  • Polymer

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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