Quantitative Analysis of 2D Polyaramid (2DPA-1) Nanoplatelets and Nanofilms Using Transmission Electron Microscopy

Abstract

Two-dimensional (2D) polyaramids with covalent in-plane extension of amide bonds offer the mechanical strength of inorganic 2D materials like graphene while retaining the solution phase synthesis of organic polymers. However, their efficient characterization remains an active area of research. Herein, we examine the 2D polyaramid 2DPA-1 synthesized via solution-phase polycondensation of melamine and a trifunctional acyl chloride. Using transmission electron microscopy, we identify and characterize thick and thin disks with diameters ranging from 0.2 to 16 nm with a median of 7.72 nm, with a mean diameter of 7.73 nm consistent with H NMR trajectory analysis. We developed computational tools for quantitative image analysis, measuring disk diameter, circularity, and electron beam extinction. Extinction values and high circularity support the presence of thin, well-defined nanodisks. Imaging of spin-coated nanofilms shows layer stacking with 0.37 nm spacing, consistent with observations from electron diffraction. Orthogonal imaging shows distinctly quantized electronic extinction similar to graphene. These findings establish a benchmark for 2D polyaramid imaging and introduce tools for extracting morphological properties, both for new aramid nanoparticle dispersions and new types of membranes and barrier materials.