Surface Of Track-etched Membranes Research Articles

Electric Discharge Synthesis of Colloidal Silver Nanoparticle Solutions Using Various Modifiers for Immobilization on the Surface of Track-Etched Membranes

Electric Discharge Synthesis of Colloidal Silver Nanoparticle Solutions Using Various Modifiers for Immobilization on the Surface of Track-Etched Membranes

Формирование на поверхности трековых мембран гидрофобных покрытий методом магнетронного распыления полимеров в вакууме

The surface properties and chemical structure of nanoscale coatings deposited on the poly(ethylene terephthalate) track-etched membranes surface by magnetron sputter deposition of ultra-high molecular weight polyethylene and polytetrafluoroethylene in vacuum are studied. It is shown that the application of coatings leads to hydrophobization of membrane surface, the degree of which depends on the type of polymer used for sputtering and the thickness of the coating. It is established that the use of this modification method leads to smoothing of structural inhomogeneities of the membrane surface layer. This result is explained by the deposition of coatings in the pore channels at a certain depth from the entrance and the overlap of pores on the surface of modified membranes. Besides, the deposition of coatings on the track-etched membrane surface leads to a change in the pore shape. The diameter of the pores on the untreated side of the membranes remains unchanged and decreases significantly on the modified side. The pores of the membranes acquire an asymmetric (conical) shape in this case. The study of the chemical structure of coatings by X-ray photoelectron spectroscopy showed that they contain oxygen-containing functional groups due to the oxidation of the polymer matrix. The developed composite membranes can be used in the membrane distillation processes for the desalination of seawater.

Deposition of Hydrophobic Polymer Coatings on the Surface of Track-Etched Membranes from an Active Gas Phase

Deposition of Hydrophobic Polymer Coatings on the Surface of Track-Etched Membranes from an Active Gas Phase

Formation of hydrophobic polymer coatings on the track-etched membrane surface

Methods of forming coatings on the hydrophilic poly(ethylene terephthalate) track-$$$etched membrane surface by means of plasma polymerization of organic compounds, magnetron sputtering and electron-beam dispersion of polymers in vacuum are considered. It is shown that the usage of compounds with low surface energy as pristine materials to coatings application allows to obtaining hydrophobic coatings on the membrane surface. The resulting composite membranes with hydrophilic and hydrophobic layers can be used in membrane distillation processes for desalination of seawater.

Hydrophobization of Track Membrane Surface by Magnetron Sputter Deposition of Ultra-high Molecular Weight Polyethylene

Method for the formation of polymer coatings on the poly(ethylene terephthalate) track-etched membrane surface by magnetron sputter deposition of ultra-high molecular weight polyethylene in a vacuum is considered. The surface morphology and chemical structure of nanoscale coatings have been investigated. It is shown that the application of the ultra-high molecular weight polyethylene-like coatings leads to hydrophobization of the membrane surface, the degree of which depends on the coating thickness. Besides, the usage of this modification method leads to smoothing of structural inhomogeneity of the membrane surface, a decrease in pore diameter, and alteration of pore shape. The investigation of the chemical structure of deposited coatings by XPS method showed that they contain a significant concentration of oxygen-containing functional groups. The composite membranes of the developed sample can be used in the process of desalination of seawater by the method of membrane distillation.

Formation of Superhydrophobic Coatings on the Track-Etched Membrane Surface by the Method of Electron-Beam Deposition of Polymers in Vacuum

Formation of Superhydrophobic Coatings on the Track-Etched Membrane Surface by the Method of Electron-Beam Deposition of Polymers in Vacuum

FABRICATION OF COMPOSITE MEMBRANES FOR WATER DESALINATION BY ELECTRON-BEAM DEPOSITION OF A POLYTETRAFLUOROETHYLENE-LIKE COATING ON THE SURFACE OF TRACK-ETCHED MEMBRANE

The present paper describes the method for the formation of polymer coatings on the poly(ethylene terephthalate) track-etched membrane surface by electron-beam deposition of polytetrafluoroethylene-like in a vacuum. It is found that the usage of this method leads to substantial hydrophobization of the membrane surface layer. The water contact angle of the deposited coatings changes from 130° to 155°, depending on the coating thickness. This change is due to the development of roughness of the deposited layer having hydrophobic properties. It is shown that the membranes of the developed sample provide a high selectivity of separation and water production rate during desalination of an aqueous salt solution of by air gap membrane distillation process and can be used for desalination of seawater.

Investigation of Morphology and Chemical Structure of Nanosized Polytetrafluoroethylene Films Deposited on the Surface of Track-Etched Membranes by Plasma Processing

The morphology and chemical structure of nanosized polytetrafluoroethylene films deposited on the surface of track-etched poly(ethylene terephthalate) membranes by means of radiofrequency magnetron sputtering and electron-beam sputtering of the polymer in a vacuum have been studied using atomic force microscopy and X-ray photoelectron spectroscopy. It has been established that the morphology of films formed with the use of these coating techniques varies considerably. This is due to the size of the deposited polymer particles. The particles formed by the electron-beam sputtering of polytetrafluoroethylene are larger than those produced by magnetron sputtering of the polymer. It has been shown that the chemical composition of the films deposited by electron-beam sputtering in a vacuum is more in line with the composition and structure of the initial polymer than the films obtained by radiofrequency magnetron sputtering.

MODIFICATION OF TRACK-ETCHED MEMBRANES BY LOW-TEMPERATURE PLASMA

Published data appearing in the last decade on the modification of track-etched membranes with the use of low-temperature plasma are considered. Some schematic description of setups and methods for sample processing in discharges of various types in atmosphere of non-polymerizing gases and by plasma polymerization, also by using of such plasma-chemical methods as magnetron sputtering of polymer targets and electron-beam dispersion of polymers in vacuum are presented. Some modern physicochemical methods for studying of changes occurring on the surface of membranes are described. Some typical examples of changes in the contact properties of the track-etched membrane surface and their chemical composition by means of X-ray photoelectron spectroscopy and Fourier-IR spectroscopy are given. Using the methods of atomic force microscopy and electron microscopy, some examples of morphological changes occurring on the surface of track membranes and in the volume of pores are presented. It is shown that the modification of track membranes by low temperature plasma leads to the creation of “smart” membranes, which possess some unique properties. This allows to significantly expand the areas of their application. Modified membranes can be used as thermosensitive elements and mechanochemical membranes with a “chemical valve”.The plasma treatment allows also significantly change the biocompatibility of the surface of track-etched membranes and use them in medicine and biology. By means of some special techniques, studies of the adsorption and growth of cellular and biological structures on the surface of modified track-etched membranes are presented.The possibility of the modified track membranes using as a highly effective biocompatible drainage material in the surgical treatment of refractory glaucoma, as well as implants in the treatment of bullous keratopathy is shown.Forcitation:Kravets L.I.,Gilman A.B. Modification of track-etched membranes by low-temperature plasma. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N 4-5. P. 4-30

Morphology and Contact Properties of Polytetrafluoroethylene-Like Films Deposited onto Track-Etched Membrane Surface in Vacuum

The surface morphology and wettability of nanoscale polytetrafluoroethylene-like films deposited onto the surface of the poly(ethylene terephthalate) track-etched membrane by RF-magnetron and electron-beam sputtering of polytetrafluoroethylene in vacuum have been studied. It was shown that the morphology of films formed with the use of these coating techniques varies considerably. This is due to the size of the deposited polymer nanostructures. The nanostructures produced by the electron-beam sputtering of polytetrafluoroethylene are much bigger in size. Investigation of the surface properties of the composite membranes obtained in these processes showns that the deposition of the polytetrafluoroethylene-like film onto track-etched membrane leads to hydrophobization of its surface. The water contact angle for the composite membranes significantly increases.<br /><br />

Structure and phase composition of thin TiO2 films grown on the surface of metallized track-etched polyethylene terephthalate membranes by reactive magnetron sputtering

We have studied TiO2, Ag, Ag/TiO2, and Cu/TiO2 coatings grown on track-etched polyethylene terephthalate membranes. The metals and oxides were deposited by reactive vacuum sputtering using a planar magnetron. The microstructure of the samples were examined by scanning and transmission electron microscopy techniques. The elemental composition of the coatings were determined by energy dispersive X-ray microanalysis, and their phase composition was determined by X-ray diffraction at different temperatures and by transmission electron diffraction. Titanium dioxide can be present on the surface of track-etched membranes (TMs) in three forms: nanocrystals of tetragonal anatase with orthorhombic brookite and amorphous TiO2 impurities. The copper-metallized TM has been shown to contain cubic Cu2O. The optical properties of the composite membranes and films have been studied by absorption spectroscopy. The energies of direct and indirect allowed optical transitions have been evaluated from measured absorption spectra of the TiO2, Ag/TiO2, and Cu/TiO2 coatings.

Enhancement of the Schottky Effect in a Si(100)—Water System Using Porous Polymeric Track-Etched Membranes

The kinetics of variation in the electronic work function (EWF) of single-crystal silicon Si(100) exposed to liquid water is studied. It is shown that immersing porous film track-etched membranes (TEMs) with pore sizes of 3.0–0.1 μm in water containing Si(100) considerably reduces the EWF of single-crystal silicon. It is found that a similar effect is observed when TEMs in the form of caps are held over the surface of water containing Si(100) at a distances of around 1.5–2.0 cm. It is speculated that the occurrence of a developed surface of TEMs in an open system changes the supramolecular structure of the water and leads to the formation of associates (H2O) n with increased dipole moments (compared to molecular moments), enhancing the Schottky effect during sorption on Si(100) surfaces.

Structural and physicochemical properties of titanium dioxide thin films obtained by reactive magnetron sputtering, on the surface of track-etched membranes

Titanium dioxide thin films have been prepared by reactive sputtering onto the surface of tracketched polyethylene terephthalate membranes using an inverted dc magnetron, and their structural and physicochemical properties have been examined. A silver film applied onto the membrane surface by physical vapor deposition has been used to protect the polymer from the photocatalytic action of titanium dioxide. The structural characteristics of the composite membranes have been studied by scanning electron microscopy, X-ray diffraction, Raman spectroscopy, spectrophotometry, and atomic force microscopy. The effects of photoinduced surface hydrophilization and catalytic decomposition of the dye rhodamine 6G have been investigated.

Novel Membrane Adsorbers with Grafted Zwitterionic Polymers Synthesized by Surface-Initiated ATRP and Their Salt-Modulated Permeability and Protein Binding Properties

A novel zwitterionic polymer functionalized porous membrane adsorber was obtained by grafting poly(N,N-dimethyl-N-methacryloyloxyethyl-N-(3-sulfopropyl) ammonium betaine) (polySPE) to poly(ethylene terephthalate) (PET) track-etched membrane surface via surface-initiated atom transfer radical polymerization (SI-ATRP). The ATRP conditions were optimized, the thus established grafting was well-controlled, and the degree of grafting could be adjusted. Functionalized membranes with a degree of grafting of about 3.5 μg/cm2 relative to the specific surface area showed almost zero values of zeta potential estimated from the trans-membrane streaming potential measurements. Typical “anti-polyelectrolyte” effect was observed for the polySPE grafted membranes. Flux through the membrane was reduced by adding chaotropic chloride and perchlorate salts to the solution which extended the polySPE chains grafted on the membrane pore wall. Perchlorate salt exhibited much stronger effect on polySPE chain conformation than chl...

Stimuli–responsive track-etched membranes via surface-initiated controlled radical polymerization: Influence of grafting density and pore size

The surface-functionalization of poly(ethylene terephthalate) track-etched membranes of different nominal pore sizes (400, 1000 and 3000 nm) with stimuli–responsive poly(2-dimethylaminoethyl methacrylate) (PDMAEMA) via surface-initiated (SI) atom transfer radical polymerization (ATRP) was performed. Variations of grafting density and grafted chain length were achieved by variation of synthesis conditions. It could be clearly demonstrated that mixtures of reaction solutions containing different ratios of acyl bromides, only one bearing the initiator group necessary for the SI ATRP, led to different initiator group densities on the resulting track-etched membrane surface which had been verified by X-ray photoelectron spectroscopy. Moreover the mass increase as function of reaction time strongly correlated with the amount of initiator bound to the membrane surface indicating that the ATRP reaction was not limited by monomer diffusion into the pores. Scanning electron microscopy images and permporometry measurements indicated an even functionalization on the entire membrane surface which was the basis for further investigations. The stimuli–responsive properties of PDMAEMA grafted track-etched membranes were studied by permeability measurements with citrate and glycine buffers as function of pH (2 and 10) and temperature (25 and 60 °C). By that the barrier properties of the membranes could be effectively changed in two steps. The results agree with the expectation that a change in grafting density and chain length has an effect on the stimuli–responsive properties of the membrane. Results for membranes having similar degrees of grafting clearly showed that the reversible swelling of grafted polymeric layers was more pronounced for lower grafting density.

Cylindrical Membrane Pores with Well-Defined Grafted Linear and Comblike Glycopolymer Layers for Lectin Binding

Glycopolymers with well-defined linear or comblike structure were grafted to poly(ethylene terephthalate) (PET) track-etched membrane surface by surface-initiated atom transfer radical polymerizati...

Ionic self-assembly of porphyrin nanostructures on the surface of charge-altered track-etched membranes

Track-etched polymer membranes are typically used as templates in the synthesis of various nanowires or nanotubes arrays. The unique advantages of track-etched membranes, such as uniform pore structure, excellent porosity, easily tailored pore sizes, and a well characterized surface chemistry, may find use in self-assembly strategies where colloidal nanostructures can be tethered to a suitable substrate to produce devices of interest. Meso-tetrakis(4-phenylsulfonicacid)porphyrin dihydrochloride and Sn(IV) tetrakis(4-pyridyl)porphyrin were used to synthesize ionic self-assembled porphyrin nanorods. The track-etched membranes surface charge was changed from negative to positive using polyethyleneimine. The porphyrin nanorods were either filtered through or self-assembled onto the surface of track-etched membranes. Comparisons were made with track-etched membranes modified with, and without, polyethyleneimine. Assembly of the porphyrin nanotubes only occurred on the surface of positively charged track-etched membranes, and filtration of the porphyrin nanorods produced a mesh-like structure on the surface of the membrane irrespective of the track-etched membrane pore diameter. In each case the characteristic absorbance profiles of the porphyrin nanorods was maintained. Transmission electron microscopy, scanning electron microscopy, atomic force microscopy, and UV-vis spectroscopy were used to characterize the various systems.

Sieve mechanism of microfiltration separation

A theoretical model of dead-end microfiltration (MF) of dilute suspensions is proposed. The model is based on a sieve mechanism of MF and takes into account the probability of membrane pore blocking during MF of dilute colloidal suspensions. An integro-differential equation (IDE) that includes both the membrane pore size and the particle size distributions is deduced. According to the suggested model a similarity property is applicable, which allows one to predict the flux through the membrane as a function of time for any pressure, and dilute concentration, based on one experiment at a single pressure and concentration. The suggested model includes only one fitting parameter, β >1, which takes into account the range of the hydrodynamic influence of a single pore. For a narrow pore size distribution in which one pore diameter predominates (track-etched membranes), the IDE is solved analytically and the derived equation is in good agreement with the measurements on different track-etched membranes. A simple approximate solution of the IDE is derived and that approximate solution, as well as the similarity principal of MF processes, is in good agreement with measurements using a commercial Teflon microfiltration membrane. The theory was further developed to take into account the presence of multiple pores (double, triple and so on pores) on a track-etched membrane surface. A series of new dead-end filtration experiments are compared with the proposed initial and modified pore blocking models. The challenge suspension used was nearly monodispersed suspension of latex particles of ∼0.45 μm filtered on a track-etched membrane with similar sized pores ∼0.4 μm. The filtered suspension concentration ranged from 0.00006 to 0.01% (w/w) and the cross-membrane pressures varied from 1000 to 20,000 Pa. Three stages of microfiltration have been observed. The initial stage is well described by the proposed pore blocking model. The model required only a single parameter that was found to fit all the data under different experimental operational conditions. The second stage corresponds to the transition from the blocking mechanism to the third stage, which is cake filtration. The latter stage occurred after approximately 10–12 particle layers were deposited (mass = 0.006 g) on the surface of the microfiltration membrane.