Analysis and Characterization of 2D Polyaramids
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quien-mgmquien-phd-cheme-2026-thesis.pdf
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Author(s)
Quien, Michelle
Advisor(s)
Strano, Michael S.
Date Issued
May 2026
Publisher
Massachusetts Institute of Technology
Abstract
Polymers that extend covalently in two dimensions (2D polymers) have been conceptualized for decades, yet their synthesis has remained elusive. Such materials promise a unique combination of the mechanical strength and barrier properties of layered inorganic materials, including graphene, hexagonal boron nitride, and molybdenum disulfide, with the low density, chemical tunability, and synthetic processability of conventional organic polymers. Our group at MIT demonstrated the first solution-phase, irreversible polycondensation route to a 2D polymer called 2DPA-1. 2DPA-1 is a 2D polyaramid whose discoidal platelets self-assemble into highly oriented, tightly packed nanofilms upon spin-coating. One property of all known polymers is that they exhibit gas permeability through the free volume of entangled chains; 2DPA-1 is the first organic polymer to break this trend. This thesis establishes the analytical, experimental, and physical foundations for understanding why, and for translating that understanding into a principled framework for the characterization, measurement, and long-term deployment of 2D polyaramid thin films as next-generation barrier materials.
First, we establish diffusion-ordered NMR spectroscopy (DOSY NMR) as a reliable and accurate tool for characterizing the size-distribution of 2DPA-1 solutions by developing custom algorithmic tools. Second, we demonstrate the molecular impermeability of 2DPA-1 spin-coated thin films, ranging from 4 to 65nm in thickness, exhibiting N2 permeability below 3.1 × 10-9 Barrer – nearly four orders of magnitude lower than the least permeable conventional polymers and approaching the H2 permeability of pristine graphene. Third, to support this end, we develop a novel interferometric deflection algorithm to study 2DPA-1 nanofilms under dynamic pressure and temperature environments, which is well beyond the current environmental capabilities of atomic force microscopy. Fourth, we further probe the ambient stability of 2DPA-1 films and failure modes of the impermeability test platform, expanding our understanding of how to measure the molecular impermeability of 2D polyaramids and other nanofilms.
Together, these new analytical tools and results expand our ability to develop novel 2D polymers and have enabled us to establish 2D polyaramids as a new class of barrier material that combines the impermeability of 2D crystals with the processability of organic polymers.
MIT Department
Massachusetts Institute of Technology. Department of Chemical Engineering
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