Influences of different preparation variables on polymeric membrane formation via nonsolvent induced phase separation

Kahrs, Catharina; Gühlstorf, Thorben; Schwellenbach, Jan

doi:10.1002/app.48852

Cited by 62 publications

(39 citation statements)

References 94 publications

(125 reference statements)

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“…The results obtained in the present study highlight that, despite being the most widely spread methodology, neglecting the ternary interaction among the components of the phase inversion process might be erroneous, particularly for polymers presenting low solubility in traditional solvents. It is also envisaged that the ternary interaction term would have an important contribution in describing the equilibrium of systems that incorporate solvents with low solubility properties, i.e., typical green solvents such as dimethylsulfoxide (DMSO) [ 55 ], PolarClean ® [ 56 ] or 2Pyr [ 6 ].…”

Section: Resultsmentioning

confidence: 99%

“… ( a ) Theoretical ternary phase diagram representing the polymer (P), the solvent (S) and the non-solvent (NS) compositions and ( b ) structures obtained depending on the precipitation pathway. Adapted from [ 5 , 6 ]. …”

Section: Figurementioning

confidence: 99%

“…The entry point (B) of the precipitation pathway into the heterogeneous phase affects the pore distribution. Depending on the pathway followed during solvent/non-solvent exchange different solid phase morphologies can occur ( Figure 1 b), i.e., dense membranes (pathway 1) were obtained when the pathway crosses the gel homogeneous region, at sufficiently high initial polymer concentration causing slow exchange due to high viscosity; binodal decomposition occurs if the precipitation pathway enters the heterogeneous phase through the metastable region, to form (pathway 2) open-cellular or closed-cellular membrane morphologies, or (pathway 4) nodular pore distributions; otherwise, spinodal decomposition takes place if the precipitation pathway enters the heterogeneous phase through the heterogeneous phase, obtaining (pathway 3) bicontinuous (lacy) distribution of pores [ 6 ]. It is deemed that, due to the significant dependence of membrane morphology on thermodynamics and kinetics of the ternary phase systems, the development of mathematical models able to predict the thermodynamic and kinetic characteristics of different polymer/solvent/non-solvent systems would facilitate the decision on the selection of membrane synthesis variables, such as initial polymer concentration, process temperature or even solvent/non-solvent combination.…”

Section: Introductionmentioning

confidence: 99%

“…Thus changes in the processing temperature affect the final membrane morphology [ 1 ]. Despite the fact that during the industrial synthesis of polymeric membranes the temperature of the polymer solution or the coagulation bath is often set different than room temperature, few works have addressed the experimental analysis of the effect of temperature on the thermodynamics of ternary systems [ 6 , 13 ]. Furthermore, there is a lack of validations of predictive models considering temperature for PVDF and few works address the temperature effect for the synthesis of PES membranes.…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, there is a lack of validations of predictive models considering temperature for PVDF and few works address the temperature effect for the synthesis of PES membranes. Kahrs et al, evaluated the influence of temperature on the thermodynamics of PES ternary systems [ 6 , 13 ]. When they compared PES membranes fabricated with N-methyl pyrrolidone (NMP) and 2-pyrrolidone (2Pyr) as the solvents, the SEM images showed an increase in the number of pores when the temperature was increased from 20 to 40 °C, because the reduction of the viscosity favored the nuclei formation in the lean-polymer phase [ 6 ].…”

Section: Introductionmentioning

confidence: 99%

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Thermodynamic Modeling and Validation of the Temperature Influence in Ternary Phase Polymer Systems

2021

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The effect of the temperature, as a process variable in the fabrication of polymeric membranes by the non-solvent induced phase separation (NIPS) technique, has been scarcely studied. In the present work, we studied the influence of temperature, working at 293, 313 and 333 K, on the experimental binodal curves of four ternary systems composed of PVDF and PES as the polymers, DMAc and NMP as the solvents and water as the non-solvent. The increase of the temperature caused an increase on the solubility gap of the ternary system, as expected. The shift of the binodal curve with the temperature was more evident in PVDF systems than in PES systems indicating the influence of the rubbery or glassy state of the polymer on the thermodynamics of phase separation. As a novelty, the present work has introduced the temperature influence on the Flory–Huggins model to fit the experimental cloud points. Binary interaction parameters were calculated as a function of the temperature: (i) non-solvent/solvent (g12) expressions with UNIFAC-Dortmund methodology and (ii) non-solvent/polymer (χ13) and solvent/polymer (χ23) using Hansen solubility parameters. Additionally, the effect of the ternary interaction term was not negligible in the model. Estimated ternary interaction parameters (χ123) presented a linear relation with temperature and negative values, indicating that the solubility of the polymers in mixtures of solvent/non-solvent was higher than expected for single binary interaction. Finally, PES ternary systems exhibited higher influence of the ternary interaction parameter than PVDF systems.

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Section: Resultsmentioning

confidence: 99%

Section: Figurementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Thermodynamic Modeling and Validation of the Temperature Influence in Ternary Phase Polymer Systems

2021

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Non‐Solvent Induced Phase Separation Enables Designer Redox Flow Battery Electrodes

et al. 2021

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devices, RFB electrolyte tanks are easily accessible, enabling electrolyte scale-up, maintenance, and potential exchange of new redox couples (Figure 1a). Despite their advantages, current iterations of RFBs are considered too costly for many emerging grid applications, [1,4,5] motivating research into improved electrolyte formulations, [6,7] separation technologies, [8][9][10] operational strategies, [11] and materials design. [12] In particular, increasing power density enables more compact and efficient reactors that can meet operational demands, reducing electrochemical stack size and costs. Within the reactor, the porous carbonaceous electrode supports several important functions, including conducting electrons and heat, providing surface area for redox reactions to occur, distributing electrolyte through the reactor, and regulating the operational pressure drop. [13] Thus, the interfacial and microstructural properties influence electrochemical and fluid dynamic performance, ultimately impacting system efficiency and cost. [14] Historically, conventional RFB electrodes have been fibrous mats derived from polyacrylonitrile (PAN) precursor and assembled into coherent structures including papers, cloths, or felts. [15] Such formats are functional for convection-driven electrochemical technologies owing to their permeability (k ≈ 10 −10 to 10 −12 m 2 ), (electro)chemical stability, and electronic conductivity. Each unique fiber arrangement results in constructs with idiosyncratic Porous carbonaceous electrodes are performance-defining components in redox flow batteries (RFBs), where their properties impact the efficiency, cost, and durability of the system. The overarching challenge is to simultaneously fulfill multiple seemingly contradictory requirements-i.e., high surface area, low pressure drop, and facile mass transport-without sacrificing scalability or manufacturability. Here, non-solvent induced phase separation (NIPS) is proposed as a versatile method to synthesize tunable porous structures suitable for use as RFB electrodes. The variation of the relative concentration of scaffold-forming polyacrylonitrile to pore-forming poly(vinylpyrrolidone) is demonstrated to result in electrodes with distinct microstructure and porosity. Tomographic microscopy, porosimetry, and spectroscopy are used to characterize the 3D structure and surface chemistry. Flow cell studies with two common redox species (i.e., all-vanadium and Fe 2+/3+ ) reveal that the novel electrodes can outperform traditional carbon fiber electrodes. It is posited that the bimodal porous structure, with interconnected large (>50 µm) macrovoids in the through-plane direction and smaller (<5 µm) pores throughout, provides a favorable balance between offsetting traits. Although nascent, the NIPS synthesis approach has the potential to serve as a technology platform for the development of porous electrodes specifically designed to enable electrochemical flow technologies.

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Dependency of polyacrylonitrile membrane structures on Hansen solubility parameters during non‐solvent induced phase separation

Zhou

et al. 2022

J of Applied Polymer Sci

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In this study, non-solvent induced phase separation (NIPS) is used to prepare polyacrylonitrile (PAN) based membranes. A thorough analysis on the correlations between coagulation conditions and membrane structures was carried out according to Hansen solubility parameters of coagulants and solvents.When coagulant is various, a larger Hansen solubility distance (R a ) between PAN and coagulant leads to a quicker phase separation and faster growth of finger-like pores. By comparison, when PAN solvent is tuned by adding small amount of water, the R a plays totally different roles for the formation of dense layer and the growth of finger-like pores. The structural variations of PAN membranes have been mapped in Hansen space according to the R a . Additionally, the low temperature induced sol-gel transition of PAN solution also affects the pore structures of the resultant membranes. These results would be helpful for better understanding the NIPS and fabricating PAN and other types of polymer membranes with desired structures and performances.

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Influences of different preparation variables on polymeric membrane formation via nonsolvent induced phase separation

Cited by 62 publications

References 94 publications

Thermodynamic Modeling and Validation of the Temperature Influence in Ternary Phase Polymer Systems

Thermodynamic Modeling and Validation of the Temperature Influence in Ternary Phase Polymer Systems

Non‐Solvent Induced Phase Separation Enables Designer Redox Flow Battery Electrodes

Dependency of polyacrylonitrile membrane structures on Hansen solubility parameters during non‐solvent induced phase separation

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