Enhanced Separation Performance of Hierarchically Porous Membranes Fabricated via the Combination of Crystallization Template and Foaming

Abstract

In this work, poly (vinylidene fluoride) (PVDF) hierarchically porous membranes (HPMs) with isolated large pores and continuous narrow nano-pores have been fabricated from its blend with poly (methyl methacrylate) (PMMA) based on the combination of crystallization template with chemical or supercritical CO2 foaming. On the one hand, the decomposition of azodicarbonamide (ADC, chemical foaming agent) or the release of CO2 can produce isolated large pores. On the other hand, PMMA is expelled during the isothermal crystallization of PVDF in their miscible blend, yielding narrow nano-pores upon etching with a selective solvent. In the case of supercritical CO2, the attained PVDF HPMs fail to improve separation performance because of the compact wall of isolated-large-pore and consequent poor connectivity of hierarchical pores. In the case of ADC, the optimal HPM exhibits much higher flux (up to 20 times) without any loss of selectivity compared with the reference only with nano-pores. The enhanced permeability can be attributed to the shorter diffusion length and lower diffusion barrier from isolated large pores, while the comparable selectivity is determined by narrow nano-pores in THE matrix.

Ceramic Foams with Controlled Geometries Through 3D‐Printed Sacrificial Templates

“…Poly(methyl methacrylate) (PMMA) is frequently used because of its lowtemperature burn-out, low ash content, and biocompatibility. [24][25][26] Porous materials achieved using PMMA with the sacrificial templating method have yielded a wide range of nanoscale pores, finding applications in catalyst materials, [27][28][29][30][31][32][33] films, [34,35] membranes, [36,37] oxides, [38][39][40] carbon-based structures, [41][42][43][44] bioactive glass, [45] electrode materials, [46,47] and scaffolds and foams. [48,49] In addition, microscale pores have been successfully fabricated using packed PMMA beads (5-800 μm) as pore-forming agents, resulting in porosities ranging from 7% to 80%.…”