Effect of mixed solvents on phase inversion of polymeric membranes

Abstract

The thermodynamics of phase inversion of polyvinylidene fluoride membrane with mixed solvents (N,N‐dimethyl formamide (DMF) and acetone) were modeled using Flory–Huggins theory. The kinetics of phase inversion were studied by measuring solvent concentration in the precipitation bath. A model was proposed to predict the time‐dependent solvent concentration profile in the precipitation bath. Depending on solvent volatility, the duration of the kinetics‐dominated regime and the evaporation‐dominated regime varies. A comparative analysis of thermodynamic and kinetic factors was used to predict membrane morphology and it was observed that the system under consideration was thermodynamics dominated. The membrane porosity exhibited decreasing porosity up to the Ac60 membrane (acetone to DMF ratio 60) and thereafter the membrane sublayer showed small pores. Addition of acetone resulted in increased crystallinity and surface hydrophilicity. The mean flow pore diameter measured using a liquid–liquid porometer decreased from 105 nm for an Ac0 membrane (acetone to DMF ratio 0) to 17 nm for an Ac60 membrane. Correspondingly, the molecular weight cut‐off of the membranes decreased from 135 kDa (for the Ac0 membrane) to 104 kDa (for the Ac60 membrane). The model proposed in this work can be used as a tool to predict the properties of intermediate compositions and prepare tailor‐made membranes with desired properties. © 2020 Society of Chemical Industry

Enhancing oil–water emulsion separation using improved styrene–acrylonitrile copolymer membrane: Experimental and thermodynamic study of the impact of solvent mixtures

“…Using the weighted average of the properties for the mixture of solvents to calculate the interaction parameters is customary by the articles, and the binodal curve can obtain with reasonable accuracy and acceptable error. 20 The method proposed by Altena et al 21 is used in order to calculate the binodal curve of the three-component membrane, including SAN30 copolymer, a mixture of DMF and NMP as solvents and water as nonsolvent. For this purpose, first, the interaction parameters of water/polymer, water/solvent, and polymer/solvent are introduced to the MATLAB software.…”

Thermosensitive Microfibril Cellulose/MnO2 Membrane: Dual Network Structure, Photothermal Smart Modulation for Switchable Emulsion Separation

“…45,46 The χ value between PVDF and DMF is lower than 0.5, which means DMF is a good solvent for PVDF. 47,48 Moreover, the interaction between PNIPAM and PVDF is thermodynamically compatible. 49 On the basis of the Flory− Huggins free energy of polymer mixing, the polymer chains can gain an increase in entropy by moving to the polymer mixture at the interface, thus prompting a more solid polymerization of PNIPAM without the influence of PVDF.…”

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Preparation of highly selective PSf/ZnO/PEG400 tight ultrafiltration membrane for dyes removal

“…Some studies added volatile solvents into the polymer solution, such as tetrahydrofuran (THF), 48 ethanol, 49 and acetone. 50 The volatile solvent generates rapid vitrification of polymer on the top layer of the membrane. As a result, a few pores and defects are formed in the membrane skin layer.…”

“…The addition of co‐solvent into the membrane solution may change the liquid–liquid demixing behavior as well as the resulting membrane structure. Some studies added volatile solvents into the polymer solution, such as tetrahydrofuran (THF), 48 ethanol, 49 and acetone 50 . The volatile solvent generates rapid vitrification of polymer on the top layer of the membrane.…”