Revealing Chemical Heterogeneity of CNT Fiber Nanocomposites via Nanoscale Chemical Imaging

Lightweight nanocomposites reinforced with carbon nanotube (CNT) assemblies raise the prospects for a range of high-tech engineering applications. However, a correlation between their heterogeneous chemical structure and spatial organization of nanotubes should be clearly understood to maximize their performance. Here, we implement the advanced imaging capabilities of atomic force microscopy combined with near-field infrared spectroscopy (AFM-IR) to analyze the intricate chemical structure of CNT fiber-reinforced thermoset nanocomposites. As an example, we unravel the chemical composition of a nanothin polymer interphase exclusively from CNT assemblies and visualize in a two- and three-dimensional format with resolution of sub-30 nm. We furthermore introduce a contact frequency map colocalized with CNTs and surrounding polymer, which might correlate the local mechanical properties with polymer chemistry and the high anisotropy of CNTs. Nanoresolved chemical imaging offers possibilities for in-depth characterization of next-generation composite materials and devices based on CNT assemblies interacting with a certain chemical environment.