Tri-continuous polymer templates enable scalable fabrication of hierarchical nanoparticle monoliths

Abstract

Hierarchical structures with bimodal porosity are crucial in diffusion and confinement-driven applications, such as catalysis and separation. This study introduces the first utilization of polymer blend nanocomposites as templates for isolating nanoparticle monoliths with bimodal porosity. We examined tri-continuous polymer blend nanocomposites of silica nanoparticles (SNPs) in polyethylene (PE), ethylene vinyl acetate (EVA), and polyethylene oxide (PEO) using three-channel confocal microscopy. This allowed visualization of their morphology and its evolution during quiescent annealing. The analysis extends to co-continuous polymer blend nanocomposites, with or without PEO. Our findings highlight the reinforcing effect of sequentially adding polymer phases in tri-continuous blends. This results in a refined morphology and strengthened three-dimensional particle network, as evidenced by a two-order-of-magnitude increase in the terminal modulus in frequency sweep rheometry. Conversely, co-continuous systems exhibit a significantly weaker particle network with a minimal increase in terminal storage modulus, making them prone to collapse during the polymer template removal. The interplay between domain size, nanoparticle jamming within one phase, and consequent particle network robustness enables the material to withstand deformation during polymer removal, facilitating the isolation of hierarchically structured monoliths. This novel templating method offers a scalable approach to fabricating hierarchically porous materials with potential applications in catalysis, energy storage, and gas separation.