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Bede Pittenger1 Sergey Osechinskiy1 Steven Ulrich1 Judy Mosley1 Sophie Loire1 Shuiqing Hu1 Thomas Mueller1

1, Bruker, Goleta, California, United States

The relationship between the microstructure and mechanical properties of microscopic domains within polymer composites is important due to their influence on macroscopic material performance and function. Mechanical properties of polymers are time dependent, so a full understanding requires measurements over a range of frequencies and temperatures. Ideally, one would like to observe the mechanical behavior of these domains while they pass through their glass transitions in order to better understand the influence of size effects and confinement.
Atomic Force Microscopy (AFM) has the nanometer level resolution and sensitivity needed to investigate these samples, but accurate comparisons with established rheological measurements have proven to be more elusive. Resonant methods like TappingMode[1] and contact resonance[2] provide mechanical property maps at discrete frequencies that are many orders of magnitude higher than bulk measurements. Non-resonant methods like force spectroscopy[3] and PeakForce Tapping[4] provide a better match in frequency, but face challenges in calculating intrinsic mechanical properties like loss tangent and storage modulus.
Recently, new AFM modes, improved modeling, better calibration, and more optimal probe design have become available[5], expanding the possibilities for quantifying mechanical properties at the nanoscale. This presentation will demonstrate the use of this new capability in examining microscopic domains and interphase regions within a polymer composite over a wide range of frequencies and temperatures.

References
[1] O. Sahin, C. Quate, O. Solgaard, and A. Atalar, Phys. Rev. B, 2004, 69, 1.
[2] U. Rabe, S. Amelio, E. Kester, V. Scherer, S. Hirsekorn, and W. Arnold, Ultrasonics,2000, 38, 430.
[3] A. Yango, J. Schäpe, C. Rianna, H. Doschke, and M. Radmacher, Soft Matter, 2016, 12, 8297.
[4] T. J. Young, M. A. Monclus, T. L. Burnett, W. R. Broughton, S. L. Ogin, and P. A. Smith, Meas. Sci. Technol., 2011, 22, 125703.
[5] B. Pittenger and D. G. Yablon, Bruker Application Note, 2017, AN149, 1.

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