Effect of Surface Modification on the Synthesis of Pore-Filling Polymeric Monoliths in Microfiltration Membranes Made from Poly(propylene) and Poly(ethylene terephthalate) (original) (raw)
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The Analyst, 2001
A novel approach towards thin-layer molecularly imprinted polymer (MIP) composite membranes was developed based on using benzoin ethyl ether (BEE), a very efficient a-scission photoinitiator. The triazine herbicide desmetryn was used as the template, and a mixture of the functional monomer 2-acrylamido-2-methyl-1-propane sulfonic acid (AMPS) and the cross-linker N,NA-methylene-bis-acrylamide (MBAA) in methanol was copolymerised via photoinitiation followed by deposition on the surface of either hydrophobic or hydrophilically precoated polyvinylidene fluoride (PVDF) microfiltration membranes. Blanks were prepared under identical conditions, but without the template. Especially, the degree of functionalization (DF) of the PVDF membranes with poly(AMPS-co-MBAA), the membrane permeabilities and non-specific vs. MIP-specific template binding from aqueous solutions during fast filtration were studied in detail to evaluate the effects of the preparation conditions, in particular the coating of the membrane surface with the photoinitiator prior to UV irradiation and the influence of the precoated hydrophilic layer on PVDF. Significant template specificities of the MIP membranes compared with the blanks were only achieved for the preparations including coating the two types of PVDF membranes with BEE. In contrast, a homogeneous photoinitiation of the copolymerisation in the membrane pore volume yielded functional layers with similar DF but with only non-specific desmetryn binding. All data clearly indicate the significant contribution of MIP stabilization by the support material in layers of optimum thickness to the MIP specificity. Main advantages of the novel approach are the potential to synthesize MIP composite membranes by controlled deposition onto any kind of polymer support, and the very fast MIP preparations due to a very efficient photoinitiator and small MIP layer thickness. Due to the mechanical and chemical stability in combination with high permeabilities, thin-layer MIP composite membranes have a large application potential, e.g., in solid phase extraction. † On leave from: Institute of Colloid and Water Chemistry, National Academy of Sciences of Ukraine, Vernadski Pr. 42, 03142 Kyiv-142, Ukraine.
Surface modified microfiltration membranes with molecularly recognising properties
Journal of Membrane Science, 2003
Polyvinilidene fluoride (PVDF-phob and PVDF-phil) and polyethersulfone (PES) microfiltration membranes were surface modified with a thin layer of molecular imprinted polymer (MIP). This material is selective to adenosine 3:5-cyclic monophosphate (cAMP) via photoinitiated copolymerisation of 2-(dimethylamino)ethyl methacrylate as a functional monomer and trimethylopropane trimethacrylate as a cross-linker in the presence of cAMP in ethanol/water solutions. The specific and non-specific template binding of MIP during filtration of aqueous solutions of cAMP was studied for membranes with different degrees of modification. It was concluded that the ability of MIP membranes to bind cAMP is a result of both the specific size and shape of recognising sites in addition to the correct position of the functional groups involved in the template binding through ionic and hydrogen binding interactions. Profile imaging atomic force microscopy and scanning electron microscopy were used to visualise surfaces and cross-sections of MIP membranes. The main advantages of this approach for MIP membrane preparation are very fast MIP layer synthesis and the possibility to obtain MIP composite membranes by controlled deposition on different kind of polymeric supports. Atomic force microscopy in conjunction with the coated colloid probe technique has been used to measure interactions between a silica sphere coated with imprinted polymer and porous supports.
Polymerization and Functionalization of Membrane Pores for Water Related Applications
Industrial & Engineering Chemistry Research, 2015
Poly(vinylidene fluoride) (PVDF) was modified by chemical treatments in order to create active double bonds to obtain covalent grafting of poly(acrylic acid) (PAA) on membrane. The attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectrum confirms the formation of conjugated CC double bonds with surface dehydrofluorination. The membrane morphology was studied by scanning electron microscopy (SEM). The surface composition was characterized by Xray photoelectron spectroscopy (XPS). The thermal stability of the dehydrofluorinated membrane (Def-PVDF) and functionalized membranes were investigated by differential scanning calorimetry (DSC) analysis. The influence of covalently attached PAA on Def-PVDF membrane has been investigated to determine its effect on the transport of water and charged solute. Variations in the solution pH show an effect on both permeability and solute retention in a reversible fashion. Metal nanoparticles were also immobilized in the membrane for the degradation of toxic chlorinated organics from water. In addition, PVDF membranes with an asymmetric and sponge-like morphology were developed by immersion-precipitation phase-inversion methods in both lab-scale and large-scale. The new type of spongy PVDF membrane shows high surface area with higher yield of PAA functionalization. The ion-capacity with Ca 2+ ions was also investigated.
Journal of Membrane Science, 2005
Poly(N-isopropylacrylamide) (PNIPAM) was successfully grafted on the surfaces and in the pores of polycarbonate track-etched (PCTE) membranes by plasma-graft pore-filling polymerization method, and the microstructure of the PNIPAM-g-PCTE membrane was investigated systematically by employing XPS, SEM, FT-IR, AFM, contact angle instrument and water flux experiments. The results showed that, the grafted PNIPAM polymers were formed inside the pores throughout the entire membrane thickness, and there was not a dense PNIPAM layer formed on the membrane surface even at a pore-filling ratio as high as 76.1%. With the pore-filling ratio increasing, the pore diameters of PNIPAM-grafted membranes became smaller. When the pore-filling ratio was smaller than 44.2%, the pores of PNIPAM-g-PCTE membranes showed thermo-responsive gating characteristics because of the conformational change of grafted PNIPAM in the pores. On the other hand, when the pore-filling ratio was larger than 44.2%, the pores of membranes immersed in water were choked by the volume expansion of the grafted PNIPAM polymers, and the membranes did not show thermo-responsive gating characteristics any longer. The critical pore-filling ratio for choking the membrane pores was in the range from 30 to 40%. The contact angle of PNIPAM-g-PCTE membrane increased from 58.5 • to 87.9 • when the temperature changed from 25 to 40 • C. The thermo-responsive gating characteristics of the water flux of PNIPAM-g-PCTE membranes were mainly dependent on the pore size change rather than the variation of membrane/pore surface hydrophilicity. easily designed and controlled, so thermo-responsive membranes received especial attention.
Preparation of porous polymer membranes using nano- or micro-pillar arrays as templates
2004
ZnO or polystyrene (PS) pillar arrays were formed on solid substrates and used as templates for the formation of porous polymer membranes. The membranes were formed by casting a polymer solution in the inter-pillar space of these templates and evaporating the solvent. Dissolution of the pillars in a selective solvent resulted in thin films containing monodisperse micrometer-sized channels. Membranes produced using the pillar template technique showed high water permeability and high size selectivity. q
Fabrication and characterisation of novel nanofiltration polymeric membrane
Materials Today Communications, 2019
A novel composite membrane was obtained by combining the products of ion-tracking and electrospinning processes. Swift heavy ions generated from a cyclotron were used to irradiate polyethylene terephthalate (PET) polymer film of thickness 23 µm to create latent tracks which were then chemically etched in an alkaline solution, to produce track-etched membrane. Magnetron sputtering was then used to deposite titanium (Ti) on the membrane to produce PET-TM with Ti thickness of ~45 nm. Polyamide 6 nanofibres (PA6-nfs) or polyacrylonitrile nanofibres (PAN-nfs) were directly electrospun upon the Ti coated PET-TM using an electrospinning process. The average fibre diameter of PA6-nfs or PAN-nfs was 52±9.8 nm or 354±40 nm, respectively. The track-etched membrane, the nanofibres and the novel composite membrane were characterised using SEM, TEM, TGA, ATR-FTIR and adsorption/desorption of nitrogen techniques. The results confirmed the fabrication of nanofibre coated track-etched composite membrane.
Journal of Membrane Science, 2005
Poly(N-isopropylacrylamide) (PNIPAM) was successfully grafted on the surfaces and in the pores of polycarbonate track-etched (PCTE) membranes by plasma-graft pore-filling polymerization method, and the microstructure of the PNIPAM-g-PCTE membrane was investigated systematically by employing XPS, SEM, FT-IR, AFM, contact angle instrument and water flux experiments. The results showed that, the grafted PNIPAM polymers were formed inside the pores throughout the entire membrane thickness, and there was not a dense PNIPAM layer formed on the membrane surface even at a pore-filling ratio as high as 76.1%. With the pore-filling ratio increasing, the pore diameters of PNIPAM-grafted membranes became smaller. When the pore-filling ratio was smaller than 44.2%, the pores of PNIPAM-g-PCTE membranes showed thermo-responsive gating characteristics because of the conformational change of grafted PNIPAM in the pores. On the other hand, when the pore-filling ratio was larger than 44.2%, the pores of membranes immersed in water were choked by the volume expansion of the grafted PNIPAM polymers, and the membranes did not show thermo-responsive gating characteristics any longer. The critical pore-filling ratio for choking the membrane pores was in the range from 30 to 40%. The contact angle of PNIPAM-g-PCTE membrane increased from 58.5 • to 87.9 • when the temperature changed from 25 to 40 • C. The thermo-responsive gating characteristics of the water flux of PNIPAM-g-PCTE membranes were mainly dependent on the pore size change rather than the variation of membrane/pore surface hydrophilicity. easily designed and controlled, so thermo-responsive membranes received especial attention.
Pore-filled nanofiltration membranes based on poly(2-acrylamido-2-methylpropanesulfonic acid) gels
Journal of Membrane Science, 2005
Strong polyacid gel-filled membranes have been prepared by UV-initiated copolymerization of 2-acrylamido-2-methylpropanesulfonic acid (AMPS) and N,N -methylenebisacrylamide within the pores of a microporous polypropylene (PP) substrate. These poly(2-acrylamido-2methylpropanesulfonic acid) (PAMPS) gel-filled membranes were readily prepared with predictable amounts of the incorporated gel polymer (mass gain, MG) provided that threshold values of the degree of cross-linking and monomer concentration were exceeded. Most of the membranes showed large dimensional changes, particularly in their thickness on incorporation of the PAMPS. These changes were related to the amount of PAMPS incorporated into the membranes. In order to determine the polymer volume fractions of the incorporated gels, the partial specific volume of PAMPS (0.575 cm 3 /g) was obtained from density measurements using pycnometry. As a result of increase in thickness (volume) of the membranes, the polymer volume fractions of the PAMPS pore-filling gels were limited to values between 0.01 and 0.06, relatively low values compared to values achieved with other gel-filled membranes based on the same substrate. The Darcy permeability of PAMPS gel-filled membranes exhibits a typical relationship with polymer volume fraction, but the absolute values obtained are much lower than those of other gel-filled membranes previously studied. The lower permeability could be attributed to tightly bound water molecules along polymer chains, which effectively enlarges the hydrodynamic size of polymer chains and narrows the channels for water transport. Using the sphere model based on the Odijk's theory of semidilute polyelectrolyte solutions, the Darcy permeability of PAMPS gel-filled membranes could be calculated with good precision.
Synthesis and characterization of porous composite membranes with hydrophilic/hydrophobic sides
Thin Solid Films, 2017
Hydrophilic/hydrophobic polymer composite membranes have known a growth of interest in various separation processes, such as desalination of water, pervaporation, reverse osmosis, gas separation, micro-and nano filtration. In this work we obtained porous hydrophilic/hydrophobic composite membranes by RF magnetron sputtering deposition of polytetrafluoroethylene-like (PTFE) thin films on one side of a polyethylene terephthalate (PET) track etched membrane, used as a porous substrate. The results show that the obtained PTFE material containing various CF x bonds is present both on the membrane surface and in its pores as a thin film, without completely covering of the pores in-depth. We proved that the membrane presents one hydrophilic side (PET) and one hydrophobic side (PTFE), with flowing characteristics (tested for gas) maintained even in the situation when the pores seems completely covered with PTFE material on the surface. .