Thermally induced phase separation in semicrystalline polymer solutions: How does the porous structure actually arise?

Pochivalov, K. V.; Basko, Andrey V.; Lebedeva, T. N.; Ilyasova, Anna N.; Yurov, Mikhail Yu.; Golovanov, R. Yu.; Артемов, В. В.; Волков, В. В.; Ezhov, A. A.; Волков, А. В.; Kudryavtsev, Yaroslav V.

doi:10.1016/j.mtcomm.2021.102558

Cited by 17 publications

(17 citation statements)

References 69 publications

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“…Polymeric membranes are widely used in the separation of various liquid streams due to their lower environmental impact and investment costs with higher energy efficiency [ 1 ]. Different polymers are used for the fabrication of filtration membranes including polysulfone [ 2 ], polyethersulfone [ 3 ], cellulose acetate [ 4 ], poly(vinylidene fluoride) [ 5 ], polypropylene [ 6 ], polyacrylonitrile [ 7 ] and others [ 8 , 9 , 10 ]. Polyacrylonitrile (PAN) is a widely used material for the fabrication of membranes for aqueous and organic liquid separation because of its good mechanical and film-forming properties, stability in solvents such as hydrocarbons, alcohols, or mild aprotic solvents, good fouling resistance, but also low cost [ 11 ].…”

Section: Introductionmentioning

confidence: 99%

Effect of Acetone as Co-Solvent on Fabrication of Polyacrylonitrile Ultrafiltration Membranes by Non-Solvent Induced Phase Separation

et al. 2022

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For the first time, the presence of acetone in the casting solutions of polyacrylonitrile (PAN) in dimethylsulfoxide or N-methyl-2-pyrrolidone was studied with regards to thermodynamical aspects of phase separation of polymeric solutions induced by contact with non-solvent (water), formation and performance of porous membranes of ultrafiltration range. The positions of the liquid equilibrium binodals on the phase diagrams of these three-component and pseudo-three-component mixtures were determined. For PAN—N-methyl-2-pyrrolidone—water glass transition curve on a ternary phase diagram was plotted experimentally for the first time. The real-time evolution of the structure of mixtures of PAN with solvents (co-solvents) upon contact with a non-solvent (water) has been studied. The thermodynamic analysis of the phase diagrams of these mixtures, together with optical data, made it possible to propose a mechanism of structure formation during non-solvent induced phase separation of different mixtures. The addition of acetone promotes the formation of a spongy layer on the membrane surface, which decreases the probability of defect formation on the membrane surface and keeps finger-like macrovoids from the underlying layers of the membrane. It was shown that the molecular weight cut-off (MWCO) of the membranes can be improved from 58 down to 1.8 kg/mol by changing the acetone content, while polymer concentration remained the same.

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Section: Introductionmentioning

confidence: 99%

Effect of Acetone as Co-Solvent on Fabrication of Polyacrylonitrile Ultrafiltration Membranes by Non-Solvent Induced Phase Separation

et al. 2022

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“…Membranes with various pore sizes have been developed, depending on the requirements of different applications. There are a few polymeric materials for ultrafiltration and microfiltration membrane preparation, namely polysulfone (PSF) [ 4 , 5 ], polyethersulfone (PES) [ 6 ], cellulose acetate (CA) [ 7 ], poly(vinylidene fluoride) (PVDF) [ 8 ], polypropylene (PP) [ 9 , 10 ], polyacrylonitrile (PAN) [ 11 , 12 , 13 ], and others [ 14 , 15 ].…”

Section: Introductionmentioning

confidence: 99%

Fabrication of Polyacrylonitrile UF Membranes by VIPS Method with Acetone as Co-Solvent

et al. 2022

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For the first time, a systematic study was carried out of the replacement of the low-volatility solvents N-methyl-2-pyrrolidone (NMP) or dimethylsulfoxide (DMSO) with the high-volatility solvent acetone in the casting solution of polyacrylonitrile (PAN). The effect of acetone’s presence in the casting solution on the performance of ultrafiltration membranes fabricated via vapor-induced phase separation (VIPS) was investigated. It was possible to replace 40% of NMP and 50% of DMSO with acetone, which resulted in the reduction of the casting solution viscosity from 70.6 down to 41.3 Pa∙s (20% PAN, NMP), and from 68.3 down to 20.6 Pa∙s (20% PAN, DMSO). It was found that 20 min of exposure to water vapor (relative humidity—85%) was sufficient to govern the phase separation, which was mainly induced by the water vapor. Regardless of the casting solution composition (15 or 20% PAN; DMSO or NMP), all membranes formed via VIPS possessed a sponge-like porous structure. The addition of acetone to the casting solution allowed the reduction of the transport pore size from 35–48 down to 8.5–25.6, depending on the casting solution composition. By varying the acetone content at constant polymer concentration, it was possible to decrease the molecular weight cut-off (MWCO) from 69 to 10 kg/mol. Membranes prepared from 20% PAN solution in an acetone/DMSO mixture had the lowest MWCO of 10 kg/mol with a water permeance of 5.1 L/(m2·h·bar).

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“…All the above factors cast into doubt the conclusions made by Dasgupta et al and motivated us to carry out our own structural and thermal studies of the PVDF–camphor mixtures. An interpretation of the data obtained for this particular system can be made in the framework of our concept proposed for the mixtures of semicrystalline polymers with low-molar-mass (LMM) compounds [ 37 , 38 , 39 , 40 ]. This concept suggests that the phase diagrams of such systems should be supplemented with an extra boundary curve reflecting the dependence of LMM substance solubility in the amorphous polymer regions on temperature.…”

Section: Introductionmentioning

confidence: 99%

“…This concept suggests that the phase diagrams of such systems should be supplemented with an extra boundary curve reflecting the dependence of LMM substance solubility in the amorphous polymer regions on temperature. This boundary curve was constructed for a number of polyolefin (low- and high-density polyethylene and polypropylene) mixtures with n-alkanes [ 40 ], alkylbenzenes [ 41 ], dialkyl phthalates [ 39 ], 1,2,4,5-tetrachlorobenzene [ 42 ], thymol [ 43 ], camphor [ 37 ], and dimethyl terephthalate [ 36 ] and for poly-3.3-bis(azidomethyl)oxetane with energetic plasticizer [ 44 ] using a quasi-equilibrium optical method. The corresponding phase diagrams allowed us to discuss the thermal behavior and structural evolution of the above mixtures in a thermodynamically consistent manner.…”

Section: Introductionmentioning

confidence: 99%

A New Look at the Structure and Thermal Behavior of Polyvinylidene Fluoride–Camphor Mixtures

et al. 2022

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An experimental quasi-equilibrium phase diagram of the polyvinylidene fluoride (PVDF)–camphor mixture is constructed using an original optical method. For the first time, it contains a boundary curve that describes the dependence of camphor solubility in the amorphous regions of PVDF on temperature. It is argued that this diagram cannot be considered a full analogue of the eutectic phase diagrams of two low-molar-mass crystalline substances. The phase diagram is used to interpret the polarized light hot-stage microscopy data on cooling the above mixtures from a homogeneous state to room temperature and scanning electron microscopy data on the morphology of capillary-porous bodies formed upon camphor removal. Based on our calorimetry and X-ray studies, we put in doubt the possibility of incongruent crystalline complex formation between PVDF and camphor previously suggested by Dasgupta et al. (Macromolecules 2005, 38, 5602–5608). We also describe and discuss the high-temperature crystalline structure of racemic camphor, which is not available in the modern literature.

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Thermally induced phase separation in semicrystalline polymer solutions: How does the porous structure actually arise?

Cited by 17 publications

References 69 publications

Effect of Acetone as Co-Solvent on Fabrication of Polyacrylonitrile Ultrafiltration Membranes by Non-Solvent Induced Phase Separation

Effect of Acetone as Co-Solvent on Fabrication of Polyacrylonitrile Ultrafiltration Membranes by Non-Solvent Induced Phase Separation

Fabrication of Polyacrylonitrile UF Membranes by VIPS Method with Acetone as Co-Solvent

A New Look at the Structure and Thermal Behavior of Polyvinylidene Fluoride–Camphor Mixtures

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