3D Imaging and Analysis of the Nanomorphology of Polymer Films to Reveal Synthesis, Structure and Property Relationships

Polyamide (PA) membranes synthesized via interfacial polymerization of acyl chloride and amine monomers develop heterogeneous crumpled morphologies. Although PA thin-film composite membranes are widely used in the water desalination industry, there is very little understanding of the relationship between this crumpled structure and the performance properties of the membranes, primarily due to the irregularity of these soft nanomorphologies. With the use low-dose electron tomography, followed by 3D reconstruction and morphometry, we strive to overcome the challenge of quantifying the crumpled nanomorphology of PA membranes, thereby uncovering relationships between synthesis, morphology, solvent permeability and mechanical properties. We probed the change in morphology of PA membranes of nine different synthetic conditions by varying the monomer concentrations. Using different morphometric approaches to quantify the crumple morphology, including curvature mapping, machine-learning-based gaussian mixture model and graph theory-based skeletonization, we were able to show a Turing instability relationship between monomer concentration and crumple morphogenesis, along with a correlation between the crumple nanomorphology with methanol permeance and apparent modulus of the PA films.