Georgian Scientists/ . 7 N 4, 2025 453 Georgian Scientists Vol. 7 Issue 4, 2025 https://doi.org/10.52340/gs.2025.07.04.28 Effect of phase inversion temperature on the formation and performance of PES/DMF/PVP polyethersulfone membranes. Nana Gogesashvili1, Giorgi Bibileishvili2, Zaza Javashvili3, Mzia Kezherashvili4, Liana Kuparadze5, Nona Butkhuzi6 Engineering Institute of Membrane Technologies of Georgian Technical University 1Doctor of Chemistry, Chief Scientist email:nanagogesashvili@gmail.com ORCID ID: https://orcid.org/0000-0001-5140-5815 2Engineering Institute of Membrane Technologies of Georgian Technical University, Doctor of Chemical and Biological Engineering, Chief Scientist email:75bibileishvili@gmail.comORCID ID:https://orcid.org/0009-0003-7712-2436 Abstract The paper studies the preparation of polymer membranes from 15% polyethersulfone solutions of PES/DMP/5%PVP and PES/DMP/7%PVP compositions using the phase inversion method at different precipitation temperatures. Two groups of polyethersulfone membranes were obtained and precipitation was carried out for each at four temperatures (10 , 20 , 30 , 40 ). The particle sizes and degree of polydispersity in the casting solutions were studied on a Malvern analyzer. The optimal temperature for conducting phase inversion at two different PVP concentrations and the influence of the coagulation bath temperature on the performance, structure, and pore size of the resulting membranes were determined. Membranes precipitated from a solution containing 5% PVP showed better performance and structure than membranes precipitated at 20 , and membranes precipitated from a solution containing 7% PVP showed better performance and structure than membranes precipitated at 30 . Keywords: Polyethersulfone, phase inversion, DMF, PVP, productivity Introduction In the phase inversion process of membrane preparation, the structure of the solid phase formed during the exchange of solvent and non-solvent in the membrane composition depends significantly not only on the nature of the solvent and non-solvent, but also on the Georgian Scientists/ . 7 N 4, 2025 454 temperature of the coagulation bath. Phase inversion is the process during which a polymer solution is transformed into a solid membrane. Temperature has a significant impact on the phase inversion process of polyethersulfone membranes, affecting both the morphology of the final membrane and the kinetics of the process. High temperatures typically increase the rate of phase separation and consequently lead to rapid dissolution of the polymer solution. This can lead to the formation of a dense membrane with a thin compact selective layer and potentially small pore sizes. At low temperatures, on the contrary, the phase inversion process slows down, giving the polymer chains more time to rearrange and resulting in membranes with porous structures with larger pores [1,2,3]. Analysis In experimental studies, polyethersulfone 5200 in dimethylformamide was used, with polyvinylpyrrolidone as an additive, which, in addition to increasing the hydrophilicity of PES membranes, also plays the role of a pore former in the phase inversion process. The concentration of the PES/DMP/PVP main polymer in the polymer composition was taken as 15%, while two concentrations of 5% and 7% by weight were selected for polyvinylpyrrolidone. Precipitation procedures were carried out separately for each composition at four temperatures. The goal was to determine the optimal temperature for conducting phase inversion at two different PVP concentrations and the effect of coagulation bath temperature on the performance, structure, and pore size of the resulting membranes. A 15% PES composition in dimethylformamide was prepared in a 100 ml flask at 50 for 24 h under constant stirring with a magnetic stirrer. The homogeneity of the solution was checked by polarizing-interference optical microscopy. Polyvinylpyrrolidone was used as an organic additive for the polymer solution, and two more compositions were prepared with the addition of 5% and 7% PVP. Precipitation of both compositions occurred at 10 , 20 , 30 , 40 . The parameters of polymer opening in the membrane compositions, particle size, concentration and degree of dispersion (PDI) of PES/DMF were determined using an instrument (Zetasizer Nano Zen 3690- Malvern Instruments, England). Figures 1, 2 and 3 show the particle intensity curves of PES compositions without additives, containing 5% and 7% PVP. In the PES/DMF composition without additive, the particle sizes are up to 100 nanometers, while in the 5% and 7% PVP-containing compositions, the particle sizes increase from 300 nm to 600 nm with increasing additive concentration. Georgian Scientists/ . 7 N 4, 2025 455 Figure 1. Particle intensity curve in PES/DMP/ solution. Figure 2. Particle intensity curve in PES/DMP/5% PV solution. Figure 3. Particle intensity curve in the PES/DMP/7%PVP composition. The resulting compositions were precipitated in water at 10 , 20 , 30 , and 40 . Infrared (IR) spectroscopy was used to analyze the chemical structure of the membranes precipitated at different temperatures. No significant differences were observed in the spectra of membranes precipitated at different concentrations and temperatures (Figures 4 and 5). Figure 4. Infrared image of the N2 membrane 34 29 .6 2 30 95 .5 0 15 78 .2 4 14 86 .2 8 14 06 .8 2 13 21 .6 0 12 97 .9 2 12 41 .3 0 11 50 .8 2 11 05 .6 1 10 72 .1 3 10 11 .4 1 87 1. 67 83 6. 06 79 6. 92 71 8. 37 70 1. 05 62 7. 28 55 6. 14 52 0. 54 41 3. 25 500100015002000250030003500 Wavenumber cm-1 0. 00 0. 05 0. 10 0. 15 0. 20 0. 25 Ab so rb an ce U ni ts Georgian Scientists/ . 7 N 4, 2025 456 Figure 5. Infrared image of the N6 membrane All membranes have similar peaks, which is due to the properties of the main polymer polyethersulfone. Because during precipitation the additive is transferred to water. Figures 4 and 5 show the spectra of the membrane samples. 621 cm-1 corresponds to C, 882 cm-1 to the unpaired bond C=C of the aromatic core. The peaks at 1150 cm-1, 1235 cm-1 and 1483 cm-1 are attributed to the sulfonic group O=S=O, while the aromatic ether group C-O-C is at 1296 cm-1. The peak at 706 cm-1 indicates the presence of a C-S bond. The morphological changes of the surface of membranes deposited at different temperatures were imaged using a scanning probe microscope. The addition of hydrophilic polyvinylpyrrolidone to the deposition solutions resulted in a change in the morphology of the resulting membranes. The surface topography of membranes deposited at a low temperature of 10 (Figures 6, 7) with both 5% and 7% PVP addition is worse than that of membranes obtained by performing phase inversion at 20 and 30 (Figures 8). On the surface of membranes deposited at 10 and 40 , roughness is observed, porosity decreases, and despite the increase in pore size, there is a decrease in performance. Figure 6. N1 membrane 34 08 .4 9 30 94 .7 8 28 78 .4 4 15 78 .1 7 14 86 .3 8 14 09 .2 5 13 21 .9 3 12 98 .1 6 12 41 .4 5 11 51 .1 9 11 05 .6 1 10 72 .1 7 10 11 .3 5 95 0. 47 87 1. 96 83 6. 71 79 7. 07 71 8. 73 70 1. 00 62 7. 36 55 6. 54 52 1. 29 41 3. 12 500100015002000250030003500 Wavenumber cm-1 0. 00 0. 05 0. 10 0. 15 0. 20 0. 25 Ab so rb an ce U ni ts Georgian Scientists/ . 7 N 4, 2025 457 Figure 7. N5 membrane Figure 8. N2 membrane Figure 9. N7 membrane The characteristics of membranes deposited from 15% polyethersulfone polymer solutions containing 5% and 7% PVP at different temperatures are given in Table 1. Georgian Scientists/ . 7 N 4, 2025 458 Table 1. Characteristics of membranes deposited at different temperatures from PES/DMP/5%PVP and PES/DMP/7%PVP systems. Polymer composition PVP, concentration% Precipitation temperature, °C Membrane Productivity l/m2h Pore size, D µm PES/DMP/PVP 5 10 N1 198 0,45 20 N2 321 0,57 30 N3 298 0,76 40 N4 163 0,77 PES/DMP/PVP 7 10 N5 142 0,63 20 N6 318 0,56 30 N7 347 0,61 40 N8 176 0,89 Result and conclusion Experimental studies have shown that the temperature of the coagulation bath is a critical parameter for the production of phase inversion polyethersulfone membranes. By controlling the temperature and other parameters, it is possible to adapt the properties and structure of the membranes to specific separation processes. Analysis of the results revealed that among the membranes precipitated from solutions containing 5% PVP, the membrane precipitated at 20 has a better structure and performance, while among the membrane samples obtained from solutions containing 7% PVP, the membrane precipitated at 30 has a better structure and performance. The result indicates that both the nature and concentration of the additive, as well as the phase inversion temperature, have a significant impact on the physicochemical characteristics of the membranes. Georgian Scientists/ . 7 N 4, 2025 459 Literature: 1.A. Al Malek, M.N. Abu Seman, D.Johnson, N.Hilal, Formation and characterization of polyethersulfone membranes using different concentrations of polyvinylpyrrolidone, Desalination, 288, 31-39 (2012) 2 J. JAGANGELO, R. TRUSSEL, M. WATSON: Role of Membrane Technology in Drinking Water, Reatment in the United, Desalination 113,119- 127, (1997). 3. C.B. Spricigo, J.C.C. Petrus, R.A.F. Machado, L.A.V. Sarmento, A. Bolsan , Preparation and characterization of polyehtersulfone membranes for use in supercritical medium, Journal of Membrane Science, v.205, 273-278,(2002) 4.G. BIBILEISHVILI, N. GOGESASHVILI, M. KEZHERASHVILI, L. KUPARADZE, Z. 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MAMULASHVILI: Effect of Different Solvents and Fore-Forming Agents on Morphology and Performance of Polyethersulphone Membranes. Oxidation Communication 47(3), 534–542 (2024). Georgian Scientists/ . 7 N 4, 2025 460 . 1, 2, 3, 4, 5, 6 1 , email:nanagogesashvili@gmail.com ORCID ID: https://orcid.org/0000-0001-5140-5815; 2 , email:75bibileishvili@gmail.comORCID ID:https://orcid.org/0009- 0003-7712-2436 15%- /5% /7% . (10 , 20 , 30 , 40 ). Malvern- . , . 5% - 20 , 7% 30 . : , , DMF, PVP,