Preparation of Highly Porous Polymer Membranes with Hierarchical Porous Structures via Spinodal Decomposition of Mixed Solvents with UCST Phase Behavior

Abstract

The predominant method to prepare polymer membranes is based on phase inversion. However, this method always leads to a dense skin with low porosity when normal polymers are used. Using the self-assembly of certain block copolymers, it is possible to prepare uniform pores with high porosity, but the prices of these polymers are too high to be afforded in practical applications. Here, we report a novel strategy to prepare highly porous and asymmetric polymer membranes using the widely used poly(vinylidene fluoride) (PVDF) as a prototype. The method combines spinodal decomposition with phase inversion utilizing mixed solvents that have the unique upper critical solution temperature phase behavior. The spinodal decomposition generates a thin surface layer containing a high density of relatively uniform pores in the mesoporous range, and the phase inversion generates a thick bulk layer composed of macrovoids; the two types of structures are interconnected, yielding a highly permeable, selective, and mechanically strong porous membrane. The membranes show an order of magnitude higher water permeance than commercial membranes and efficient molecular sieving of macromolecules. Notably, our strategy provides a general toolbox to prepare highly porous membranes from normal polymers. By blending PVDF with cellulose acetate (CA), a highly porous PVDF/CA membrane was prepared and showed similarly high separation performance, but the higher hydrophilicity of CA improved the membrane flux in the presence of proteins.

Protection of Lithium Anode by a Highly Porous PVDF Membrane for High-Performance Li–S Battery

“…The detail membrane preparation procedure and the pore-forming mechanism can be found in previous work. 27 The Fourier transform infrared spectra (FTIR) in Figure 1c revealed that the PVDF membrane contained α, β, and γ three types of crystalline phases. Figure 1d shows the uptake curve of the PVDF membrane versus time with the electrolyte of 1 M LiTFSI in DOL/DME.…”

Emulsion templated scaffolds of poly(ε-caprolactone) – a review

“…1 depicts the significance of porous polymers, as an increasing trend in the number of publications devoted to porous polymers is observed in the last decade. Ease of melt or solution processing of polymers in various shapes and sizes and feasibility for chemical modifications have made them a material of interest for developing different porous architectures in the form of electrospun fibres, 4 membranes, 5 beads, 6 monoliths, 7 etc. Porous polymers adorned with several fascinating properties like low specific density, high specific strength, high surface area and controlled porosity with tunable pore-size have thus been used in numerous household and industrial applications as adsorbents, 8 membranes for water purification, 9 gas storage, 10 catalysis, 11 sensors, 12 precursor materials for porous carbons, 13 packaging materials in chromatography columns, 14 encapsulating agents for controlled drug release 15 and scaffolds for tissue engineering, 16 to name a few.…”

Optimization of Oil Adsorption Capacity by Aerogel Powder Synthesized Using Emulsion Droplets as Micro-reactors in Ambient Conditions from Sodium Silicate as Precursor

“…Porous materials have attracted wide attention because of their useful functionalities and microstructures for various applications in including catalytic supports, thermal insulators, sound absorbers, adsorbents, energy materials, and separation membranes [1][2][3][4][5][6]. For several decades, the synthesis routes of porous materials have typically involved chemical approaches, such as the hydrothermal method, sol-gel method, and gasphase synthesis like the spray pyrolysis method [7][8][9][10].…”