Beyond nothingness in the formation and functional relevance of voids in polymer films

FC Kalutantirige and JL He and LH Yao and S Cotty and S Zhou and JW Smith and E Tajkhorshid and CM Schroeder and JS Moore and H An and X Su and Y Li and Q Chen, NATURE COMMUNICATIONS, 15, 2852 (2024).

DOI: 10.1038/s41467-024-46584-2

Voids-the nothingness-broadly exist within nanomaterials and impact properties ranging from catalysis to mechanical response. However, understanding nanovoids is challenging due to lack of imaging methods with the needed penetration depth and spatial resolution. Here, we integrate electron tomography, morphometry, graph theory and coarse- grained molecular dynamics simulation to study the formation of interconnected nanovoids in polymer films and their impacts on permeance and nanomechanical behaviour. Using polyamide membranes for molecular separation as a representative system, three-dimensional electron tomography at nanometre resolution reveals nanovoid formation from coalescence of oligomers, supported by coarse-grained molecular dynamics simulations. Void analysis provides otherwise inaccessible inputs for accurate fittings of methanol permeance for polyamide membranes. Three- dimensional structural graphs accounting for the tortuous nanovoids within, measure higher apparent moduli with polyamide membranes of higher graph rigidity. Our study elucidates the significance of nanovoids beyond the nothingness, impacting the synthesis-morphology- function relationships of complex nanomaterials. Voids are known to impact the properties of materials, but the nanovoids also present are less well understood than macroscopic voids. Here, the authors utilise 3D imaging and graph theory to study nanovoid formation and impact on material properties.

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