Preparation of PVDF/poly(tetrafluoroethylene‐co‐vinyl alcohol) blend membranes with antifouling propensities via nonsolvent induced phase separation method

Poly(vinylidene fluoride) (PVDF) was blended with a new amphiphilic copolymer, poly(tetrafluoroethylene‐co‐vinyl alcohol) [poly(TFE‐VA)], via non‐solvent induced phase separation (NIPS) method to make membranes with superior antifouling properties. The effects of the VA/TFE segment ratio of the copolymer and the copolymer/PVDF blend ratio on the properties of the prepared membranes were studied. Membranes with similar water permeabilities, surface pore sizes, and rejection properties were prepared and used in bovine serum albumin (BSA) filtrations with the same initial water flux and almost the same operating pressure, to evaluate the sole effect of membrane material on fouling propensity. While the VA/TFE segment ratio strongly affected the membrane antifouling properties, the effects of the copolymer/PVDF blending ratio were not so drastic. Membrane surface hydrophilicity increased, and BSA adsorption and fouling decreased upon blending a small amount of amphiphilic copolymer with a high VA/TFE segment ratio with PVDF (copolymer/PVDF blending ratio 1:5). © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43780.     

Preparation of porous silicon rubber membranes by breath figure method

A series of porous silicon rubber membranes with regularity and uniform size had been prepared by breath figure method form polydimethylsiloxane and hydrogen silicon oil (Si-H1341). Hydrophilicity and hydrophobicity of polymer, different methods of cast films, co-solvents, solid particle dispersants, temperature, solution concentration, and molecular weight of silicon rubber are considered and discussed in the article to analyze effects of experiment situations on porosity of porous silicon rubber membranes. Remarkably, using the method of blending silicon rubber with branch hydrophilic silica-gel, large area hydrophilic modification of the silicon rubber can be achieved, and it is easy to form pores with regular structure. With synergies of co-solvents, the excellent porosity with more rounded pore shape and better regularity is acquired. The results indicate that the pore size of the silicon were affected greatly by the addition of co-solvent, the boiling point of solvent, molecular weight of raw materials, and reaction temperature. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47912.     

Interfacial tuning and designer morphologies of microporous membranes based on polypropylene/natural rubber nanocomposites

Microporous polypropylene (PP) nanocomposite membranes are in great demand in various fields such as energy harvesting, water purification, and other industrial applications. Thin films of PP/natural rubber (NR) blend nanocomposite have been prepared by melt mixing and the membranes are made porous by extracting the NR phase from the blend. The present study gives a better insight into the nanoparticle shape and localization-tailored porous morphology of PP membrane. Thermodynamic prediction of nanofiller localization and its impact on morphology were studied. 2D clay platelets in PP matrix tune the morphology of the porous membrane into lamellar, whereas spherical nanofillers give elongated spherical pores. The localization of nanoparticles was observed using transmission electron microscope, which is also confirmed from theoretical prediction of localization of nanofillers with the help of interfacial energy and surface tension. Thermal studies reveal that nanofillers enhance the thermal stability of polymers. Mechanical studies reveal that nanoparticles improve the mechanical properties of the system. 2D platelet shaped-nanofillers enhance the mechanical strength of the polymer up to 39%, which is higher than that obtained for 3D spherical nanofillers. Nanofiller shape and localization have a great influence in deciding the properties and porosity of the membrane.     

Effects of the support‐layer hydrophilicity on the active‐layer formation of composite membranes

To understand the effects of the hydrophilicity of the support layer on the formation of the active layer and the performance of composite membranes, a support layer was prepared from a polysulfone (PSf) blend with a hydrophilic copolymer, and then its top surface was overcoated with an active layer fabricated by an interfacial reaction of m‐phenylenediamine (MPDA) with trimesoyl chloride. The time required for impregnating the support layer with an aqueous solution containing MPDA was gradually decreased by increases in the hydrophilicity of the support layer. The required soaking time was greater than 9 min for the formation of the defect‐free active layer when the support layer prepared from PSf was used, whereas it could be reduced about 1 min by the use of the hydrophilic support layer. Furthermore, composite membranes prepared with the PSf/hydrophilic copolymer blend as the support layer always exhibited higher salt rejection and water permeability than those prepared with PSf as the support layer. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Proton‐conductive membranes based on vanadium substituted heteropoly acids with Keggin structure and polymers

In this article, novel proton‐conducting composite membranes SPEEK/PW₁₁V and PVA/SiW₁₁V were synthesized from vanadium substituted heteropoly acids (H₄PW₁₁VO₄₀·8H₂O and H₅SiW₁₁VO₄₀·15H₂O, abbreviated as PW₁₁V and SiW₁₁V) and polymers (SPEEK or PVA) at the weight ratio 70 : 30. The membranes were characterized by the infrared spectroscopy, X‐ray powder diffraction, and scanning electron microscopy, which confirmed the maintenance of the Keggin framework and dispersion homogeneously in the polymer matrix without long‐range ordering. Their proton‐conducting properties were investigated with electrochemical impedance spectroscopy. The results show that the respective proton conductivities of SPEEK/PW₁₁V and PVA/SiW₁₁V membranes were in the order of 10^?2 and 10^?4 S cm^?1 at ambient temperature. The temperature dependence of the two composite membrane electrolytes exhibit Arrhenius behavior, and the observed activation energies to be 15.82 kJ mol^?1 for SPEEK/PW₁₁V and 14.40 kJ mol^?1 for PVA/SiW₁₁V, which indicates that the proton conduction complies with the Grotthuss mechanism. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42204.     

Preparation and characterization of sulfonated polyetherimide/polyetherimide blend membranes

Polyetherimide (PEI) was sulfonated by chlorosulfonic acid (CSA) in 1,2‐dichloroethane for the first time. With the increase of the CSA/PEI repeat unit ratio and/or reaction time, the ion‐exchange capacity (IEC) of the sulfonated polyetherimide (SPEI) increased accordingly. Water‐uptake testing and contact‐angle measurement showed that the hydrophilicity of the SPEI increases with the increase of the IEC. Membranes were fabricated from SPEI/PEI blends with different ratios. The morphologies of the blend membranes were examined by scanning electron microscopy, which showed that the membrane pore size is larger when SPEI with higher IEC was used. With the increase of SPEI ratio in the blend membranes, the membrane pore size also increased. The contact‐angle data of the membranes showed that the hydrophilicity of the blend membrane was elevated because of the sulfonate group on the SPEI molecular backbone. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1709–1715, 2004     

A new method of preparing superabsorbent PVF porous foam through the simultaneous acidification of water glass solution–aspect of environmental protection

To reduce the wastewater pollution problem, silica particles that have resulted from simultaneous sulfuric acidification of water glass solution serve as the pore‐forming agent for preparing superabsorbent PVF/SiO₂ foam in this study. This is a departure from the traditional porous PVF/starch foam's manufacture method. The pore structure of PVF/SiO₂ foam is very different from that of PVF/starch foam. The effect of the concentration of these pore‐forming agents on the pore structure, mechanical modulus, and water adsorption capacity of PVF/starch and PVF/SiO₂ foams are investigated in this study. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39894.     

Preparation of hydrophilic dimethyl 5‐sodium sulfoisophthalate/poly(ethylene terephthalate) nanofiber composite membranes for improving antifouling properties

In this study, the effect of dimethyl 5‐sodium sulfoisophthalate (SSI) nanoparticles (NPs) on the antifouling properties of poly(ethylene terephthalate) (PET) electrospun nanofiber membranes (ENMs) was investigated through the ultrafiltration of C. I. Basic Blue 3. 3 dye. To reveal the tortuous effect of this additive on the antifouling properties, scanning electron microscopy was used for the characterization of the ENM structure and the optimization of the SSI NP content. Then, some selected physical and structural properties of the membrane, such as the porosity, moisture regain, contact angle, hydraulic permeability (L _p ), and mechanical properties, in the optimized range of SSI NP contents were investigated. Finally, the influence of this additive on the rejection and flux recovery ratio of the prepared membranes was considered. Consequently, the antifouling properties were assessed with consideration of all of the aforementioned parameters. The SSI/PET2 membrane (that with 0.02% w/w SSI NPs with respect to the total amount of PET polymer and SSI NPs), with an average nanofiber diameter of 450 nm, a porosity of 78.44%, a moisture regain of 9.34%, a contact angle of 86.48°, an L _p of 42,167 L h^?1 m^?2 bar^?1, a tensile strength of 4.66 ± 0.04 MPa, a flux recovery ratio of 15.3%, and a final rejection of 95%, showed a significant enhancement in the antifouling properties compared with pristine PET ENMs. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44522.     

Variable infrared emissivity based on polyaniline electrochromic device influenced by porous substrate

Polyaniline (PANI) films and its electrochromic devices based on various porous substrates were obtained by electrochemical deposition. The pore size distribution of the porous substrate has shown important influence on the infrared emissivity variation (∆ε) of the device. Morphology and structure of PANI were characterized by scan electronic microscopy (SEM) images and Fourier transform infrared spectra (FTIR). SEM images present the morphology difference of PANI on different substrates, which suggest that large pores will prevent PANI particles from forming orderly and compactly films. FTIR spectrum indicates that pore size of substrates affects the orientation of PANI chains. Furthermore, electrochemical properties and stability of PANI films were analyzed by cyclic voltammetry (CV) curves. And the CV curve revealed that the generation of irreversible degradation products is the reason for poor stability of PANI films. Finally, greatly improved ∆ε of 0.559 in 3–5 μm waveband and 0.39 in 8–14 μm waveband is achieved by choosing a small pore substrate.     

Separation of oil/water emulsions using nano MgO anchored hybrid ultrafiltration membranes for environmental abatement

This work focuses on utilizing the dual role of sulfonated polyphenyl sulfone (SPPSU) as both an anchoring agent and an interlayer modifying agent in the preparation of nano MgO/SPPSU/PPSU membranes for oil removal from water. These asymmetric membranes were prepared using the phase inversion technique. The dispersed nano MgO was observed in the membrane matrix as seen by scanning electron microscope and energy dispersive X‐ray analysis. The reduction in contact angle value establishes the increases in hydrophilicity. An increase in SPPSU (wt %) loosens the nano MgO/SPPSU/PPSU membrane packing as exhibited by the increase of d‐spacing by X‐ray diffraction analysis. The antifouling properties were tested using humic acid, as a model foulant. Further, in castor oil/water emulsion separation, it was found that the membrane with 25 wt % anchored moiety SPPSU/nano MgO produced a greater flux recovery ratio of 94.9% (±0.3) without compromising the oil rejection of 99% (±0.4) and better oleophobic surfaces for oil. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 132, 42848.     

Preparation and characterization of water‐soluble polymers and their utilization in chromium sorption

In this article, we study the sorption of chromium from aqueous solutions using water‐soluble polymers (WSPs): poly[2‐(acryloyloxy) ethyl] trimethylammonium chloride, P(ClAETA); poly[2‐(methacryloyloxy) ethyl] trimethylammonium methyl sulfate, P(SAETA); and poly(sodium 4‐styrenesulfonate), P(NaSS). These WSPs were obtained by radical polymerization and purified by fractionation through ultrafiltration membranes with different molar mass cut‐offs (30 and 100 kDa). The characterization was carried out by thermogravimetric analysis (TGA), FTIR, and ¹H‐NMR spectroscopies and scanning electron microscopy/energy dispersive X‐ray spectroscopy. The chromium retention properties of the polymers were determined in terms of pH, optimal polymer concentration, and the effect of interfering ions. The results show yields above 80% for all of the synthesized WSPs. Characterization by spectroscopy confirmed the chemical structure of the polymers. TGA shows thermal decomposition temperatures of 264 and 324 °C for P(ClAETA) and P(SAETA), respectively. In the case of P(NaSS), the first thermal decomposition begins at approximately 450 °C. Maximum retention of Cr(VI) (100%) by the polymers P(ClAETA) and P(SAETA) was achieved at pH 9, and the maximum retention of Cr(III) (100%) was achieved by P(NaSS) at pH 3. The optimal polymer:Cr molar ratio obtained was 20:1. The retention of chromium(VI) was decreased by the presence of interfering ions, and the hydrodynamic flux was almost constant during ultrafiltration. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45355.     

Preparation and characterization of porous titanium dioxide sulfonated polystyrene composite microspheres with amphiphilicity

Porous particles with amphiphilicity were prepared by a nonpolymeric pore‐formation process with the sulfonation of polystyrene microspheres. Nano titanium dioxide (TiO₂) particles were then grafted onto the surface via a sol–gel method to finally form the composite particles. The effects of the mass ratio of ethanol (EtOH) to water, temperature, and solubility parameter on the pore‐formation process is discussed in detail. The morphology, porous structure, and wetting properties of the particles were studied by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared (FTIR) spectroscopy, and contact angle measurement. The results show that porous sulfonated polystyrene (SP) microspheres could be fabricated at 60°C with a 1 : 1 mass ratio of EtOH–water and a solubility parameter of 29.69 MPa^1/2. The TiO₂ particles were determined to be grafted onto the SP microspheres by physical‐bond interaction on the basis of FTIR analysis. The contact angles for both water (aqueous‐phase) and various organic solvent (oil‐phase) droplets with different polarities on the surface of compressed tablets of TiO₂–SP powder were all lower than 30°; this indicated excellent amphiphilicity in the composite particles. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Fabrication of antifouling membranes by blending poly(vinylidene fluoride) with cationic polyionic liquid

Membrane fouling problem is now limiting the rapid development of membrane technology. A newly synthesized cationic polyionic liquid (PIL) [P(PEGMA-co-BVIm-Br)] was blended with poly(vinylidene fluoride) (PVDF) to prepare antifouling PVDF membranes. The PVDF/P(PEGMA-co-BVIm-Br) exhibited an increased surface hydrophilicity, the water contact angle was reduced from 77.8° (pristine PVDF) to 57.9°. More porous membrane structure was obtained by adding PIL into the blending polymers, as high as 478.0 L/m²·h of pure water flux was detected for the blend PVDF membrane in comparison with pristine PVDF (17.2 L/m²·h). Blending of the cationic PIL with PVDF gave a more positive surface charge than pristine PVDF membrane. Blend membranes showed very high rejection rate (99.1%) and flux recovery rate (FRR, 83.0%) to the positive bovine serum albumin (BSA), due to the electrostatic repulsion between the membrane surface and proteins. After three repeated filtration cycles of positive BSA, the blend PVDF membranes demonstrated excellent antifouling performance, the permeation flux of the membranes was recovered very well after a simple deionized water washing, and as high as 70% of FRR was obtained, the water flux was maintained at above 350 L/m²·h. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48878.     

The impact of nonpolar coagulation bath‐immiscible liquid additives on the polyethersulfone membranes structure and performance

In this study, the impact of several normal alkanes as additives on the structural parameters and the morphologies of flat sheet PES membranes were investigated. The asymmetric membranes were fabricated by phase inversion method. Also n‐hexane, n‐decane, and n‐tetradecane were used as additives. The effects of different concentrations of these additives were investigated by producing the ternary phase diagrams. Further the membranes were characterized by means of solute transport test, contact angle, pure water flux, porosity measurement, and scanning electronic microscopy. It was expected that two distinct phase inversions to be occurred since both the polymer and the additives were insoluble in the coagulation bath. Observations revealed that n‐hexane and n‐decane were less effective compared with n‐tetradecane in terms of binodal shifting toward PES/NMP axis. In conclusion, it was revealed that the coagulation bath immiscible‐liquid additives had a major impact on the membranes structure in order to achieve the enhanced properties. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44509.     

Influences of extractant on the hydrophilicity and performances of HDPE/PE‐b‐PEG blend membranes prepared via thermally induced phase separation (TIPS) process

Blending the block copolymer into the membrane matrix is a convenient and efficient way for membrane modification. In this study, HDPE/PE‐b‐PEG membranes were prepared via TIPS process, and the extractant effect was investigated. An interesting finding was that a non‐polar extractant (n‐hexane) was more conducive to the surface enrichment of PEG chains than a polar solvent (ethanol). The reason was deemed to be the combined effect of entropy drive, interfacial energy, and the swelling behavior. Besides, membrane performances related to the surface chemical properties were studied. Results suggested that the prepared blend membranes extracted by n‐hexane showed enhanced hydrophilicity, anti‐fouling property and water flux. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2680–2687, 2013     

Advanced porous polyphenylsulfone membrane with ultrahigh chemical stability and selectivity for vanadium flow batteries

Porous polyphenylsulfone (PPSU) membranes are facilely prepared via the nonsolvent-induced phase separation method. The typical asymmetric structure of such prepared porous membranes can be controlled by optimizing the sulfonation degree of the sulfonated poly(ether ether ketone) to 84.7% in the casting solution. Scanning electron microscopy images show that the porous membrane comprises a thin dense top skin layer, a sublayer structure with distinct long finger-like pores and the large pores in the substructure. The porous PPSU membrane was then used in vanadium flow battery (VFB). The optimized porous membrane yields an admirable performance, including excellent selectivity, chemical stability, and high columbic efficiency. Furthermore, the low cost of porous PPSU membranes indicates the promise of this technology for use in VFB applications. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47752.     

Study on the preparation and thermal shrinkage properties of nano‐SiO2/UHMWPE/HDPE blend microporous membranes

Nano‐SiO₂/UHMWPE/HDPE blend microporous membranes (NBMs) with different content of nano‐SiO₂ particles were prepared via thermally induced phase separation process. Thermogravimetric analysis was used to investigation of the amount of nano‐SiO₂ particles reserved in NBMs. This approach showed that about 59% of total content of nano‐SiO₂ particles reserved in NBMs. The formation and development of the interface pores were studied by scanning electron microscopy. NBMs performance was characterized by a variety of metrics including thermal shrinkage, melting and crystallization behavior, porosity and pore diameter, and permeability. The results indicated that nano‐SiO₂ particles served as nucleating agent increasing the crystalline of NBMs. The comprehensive properties of NBMs were optimum when the content of nano‐SiO₂ particles was 1%. Compared with pure HDPE separators, NBMs exhibit higher porosity and lower thermal shrinkage due to its high crystalline and the enrichment of UHMWPE chains. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41321.     

Effects of bath temperature on the morphology and performance of EVOH membranes prepared by the cold‐solvent induced phase separation (CIPS) method

The development and characteristics of porous EVOH membranes by cold‐solvent induced phase separation (CIPS) process were investigated. Binary dopes of 1,3‐propandiol/EVOH prepared at 80 °C were immersed in 1,3‐propandiol at a lower temperature to engender polymer precipitation. The quench temperature affects phase separation modes, and hence structure and performance of resulting CIPS membranes. When the bath temperature was set below the crystallization line and above the binodal (e.g. 45 °C), the formed membrane was dominated by a packing of semicrystalline EVOH globules. When the bath was set at a temperature just below the spinodal (e.g. 20 °C), spinodal decomposition (SD) dominated the precipitation process to give a lacy‐like bicontinuous structure; yet there is also a clear imprint from polymer crystallization. When the bath temperature was set deeply within the spinodal dome (e.g. 5 °C), polymer crystallization affected only little the SD‐derived bicontinuous morphology. Water permeation flux, wettability, tensile strength, and ultra‐filtration experiments of the membranes were conducted. The results indicated that those properties were closely correlated with the porosity level, pore size, and membrane morphology. Moreover, X‐ray diffraction and DSC analyses indicated that the formed membranes had a crystallinity of 38 to 42%, consistent with the literature data. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44553.     

Correlation of the polymer hydrophilicity and membrane fabrication process on the properties of asymmetric membranes in a vapor‐induced phase‐inversion process

In this study, we sought a better understanding of how the hydrophilicity of a polymer affects the morphology and performance of membranes. Three types of polymer with different hydrophilicity solution systems were considered: poly(aryl ether ketone) bearing a hydroxyl group (PEK–OH‐100) with N,N ‐dimethylformamide (DMF); poly(aryl ether ketone) bearing a 50% fraction hydroxyl group with DMF, and cardo poly(aryl ether ketone) with DMF. These systems were used to investigate the evolution of the morphology and variation in performance versus a change in the hydrophilicity of the polymer. In addition, the fundamental thermodynamic influence of the solution systems on the phase‐inversion process was investigated by cloud‐point measurement and Hansen solubility parameter theory to determine the role of polymer hydrophilicity on the stability of the polymer solution in humid surroundings. The performance of the membranes was tested via testing of the pure water flux, porosity, and rejection of bovine serum albumin (BSA) with respect to variations in the polymer hydrophilicity, evaporation time, relative humidity, and molecular weight of the polymer. The resulting optimal membrane exhibited a flux of 329.3 L m^?2 h^?1 and a 99.3% rejection of BSA at a relative humidity of 90% and an evaporation time of 3 s. The hydrophilic PEK–OH‐100 membranes have promising applications in protein separation and the porous support of reverse‐osmosis membranes and so on. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44701.     

Effects of the extractant on the hydrophilicity and performance of high‐density polyethylene/polyethylene‐b‐poly(ethylene glycol) blend membranes prepared via a thermally induced phase separation process

The blending of a block copolymer into the membrane matrix is a convenient and efficient way to modify membranes. In this study, high‐density polyethylene/polyethylene‐b‐poly(ethylene glycol) (PEG) membranes were prepared via a thermally induced phase separation process, and the extractant effect was investigated. An interesting finding was that the nonpolar extractant (n‐hexane) was more conducive to the surface enrichment of the PEG chains than the polar solvent (ethanol). The reason was deemed to be the combined effect of the entropy drive, interfacial energy, and swelling behavior. In addition, the membrane performance related to the surface chemical properties was studied. The results suggest that the prepared blend membranes extracted by n‐hexane showed enhanced the hydrophilicity, antifouling properties, and water flux. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3816–3824, 2013