Pushing AFM to the Boundaries: Interphase Mechanical Property Measurements near a Rigid Body

作者：I. Saito, Richard J. Sheridan, Stefan Zauscher, L. Catherine Brinson · 发表于：Macromolecules · 年份：2024 · DOI：10.1021/acs.macromol.4c01993 · 被引用次数：11 · 研究领域：Adhesion, Friction, and Surface Interactions、Metal and Thin Film Mechanics、Force Microscopy Techniques and Applications

Understanding the mechanical properties of polymer nanocomposite materials is essential for industrial use. Particularly, the determination of the polymer modulus at the nanofiller–polymer interphase is important for optimizing the interfacial mechanical properties. Nanoindentation via Atomic Force Microscopy (AFM) is well-established for measuring the modulus of the interphase region with nanoscale spatial resolution. However, indentation into heterogeneous materials presents a confounding issue often referred to as the “substrate effect”, i.e., the structural stress field caused by the rigid body is convoluted with the actual modulus of the interphase region. While finite element analysis (FEA)-based methods can be used to deconvolute the interphase modulus from measured apparent modulus–distance profiles, the experimental validation of this method is still needed. Here, we provide this validation using AFM nanoindentation on a layered model composite that consists of three layers with different moduli to recapitulate the properties of the matrix, the filler, and the interphase of real polymer nanocomposites. By systematically varying the thickness of the “artificial” interphase layer and the AFM probe radius, we obtain modulus–distance profiles over a wide range of indentation conditions. We validate a method to deconvolute the substrate effect using an empirically derived master curve obtained from FEA analysis. Furthermore, we showed that the effect of the artificial int...