Size Dependent Mechanical Behavior of Free-Standing Glassy Polymer Thin Films

Abstract

Mechanical properties of nanoscale free-standing polymer thin films exhibit size-dependence due to surface effects. However, it has remained a challenge to associate the length scales where such differences emerge with bulk polymer properties. Here we utilize molecular dynamics simulations to uncover the dependence of elastic modulus of freestanding films on film thickness and bulk properties. Comparison of glass transition temperature (Tg) and modulus (E) indicates that Tg converges to bulk value slightly faster as 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. Our simulations suggest that the length scale of perturbation of free surface is only about several nanometers, but the effect is large enough that only films of 100 nm or larger exhibit negligible surface effects.

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Document Details

Document Type
Technical Report
Publication Date
Aug 31, 2014
Accession Number
ADA622470

Entities

People

  • Sinan Keten
  • Wenjie Xia

Organizations

  • Northwestern University

Tags

Communities of Interest

  • Advanced Electronics
  • Energy and Power Technologies

DTIC Thesaurus Topics

  • Chemistry
  • Composite Materials
  • Films
  • Glass Transition Temperature
  • Materials Science
  • Measurement
  • Mechanical Engineering
  • Mechanical Properties
  • Modulus Of Elasticity
  • Molecular Dynamics
  • Polymer Chemistry
  • Polymeric Films
  • Polymers
  • Relaxation Time
  • Simulations
  • Thin Films
  • Transition Temperature

Fields of Study

  • Physics

Readers

  • Fluid Dynamics.
  • Nanocomposite Materials Science
  • Polymer Science and Engineering.