Non-classical diffusion of PDMS confined in a surface forces apparatus

ORAL

Abstract

We present FRAP measurements inside a surface forces apparatus. Polydimethylsiloxane (PDMS), well above its glass transition, was confined into molecularly-thin films between atomically smooth mica sheets. Translational diffusion was measured using fluorescence recovery after photobleaching (FRAP) as the polymer film thickness was changed from tens of Rg to 3 Rg . The FRAP recovery curves of confined films are distinctly non-classical. Huge heterogeneity is suggested by stretched exponential behavior in which the power of time varies smoothly from $\beta $=1 (thick films) to $\beta $=0.3 (confined films) with a sharp transition between these limits.

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Authors

  • Subhalakshmi Kumar

    University of Illinois, Urbana-Champaign

  • Changqian Yu

    University of Illinois, Urbana-Champaign, Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign

  • Sung Chul Bae

    University of Illinois, Urbana Champaign, Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, University of Illinois at Urbana Champaign

  • Steve Granick

    U of Illinois-Urbana Champaign, University of Illinois, Urbana Champaign, Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, University of Illinois at Urbana Champaign, University of Illinois at Urbana-Champaign