Quantitative measurements of local polymer stiffness via atomic force microscopy (AFM) can be convoluted by stress field interactions with particles or substrates near the probe tip. This phenomenon is often termed the “substrate effect” or “thin film effect.” We demonstrated an empirical master curve methodology to model the change in measured modulus due to these effects in carbon black-styrene butadiene rubber nanocomposites. Finite element analysis in conjunction with experimental AFM data across interfaces at varying indentation depths enables the detection of an interphase layer and reasonable estimation of the interphase width when present. While the technique was demonstrated for polymer nanocomposites, we expect the strategy to be broadly applicable to multiphase soft materials.
Active Researcher on the Project:
 Collinson, D. W., Eaton, M. D., Shull, K. R., & Brinson, L. C. (2019). Deconvolution of Stress Interaction Effects from Atomic Force Spectroscopy Data across Polymer− Particle Interfaces. Macromolecules, 52(22), 8940-8955.