B. V. Mchedlishvili

The heavy ion tracks in polymers investigation by means of high-effective liquid chromatography and atomic-force microscopy

Abstract The method of heavy high-energy ions latent tracks structure in polymers investigations have been proposed. This method includes the irradiated polymer preliminary treatment with water, then with week alkali solution for different track area visualization and investigation. The products of polyethylene terephthalate radiolysis from the track areas were investigated by means of inverse-phase chromatography. Atomic-force microscopy was used for surface change of initial and developed polymer investigation. It was shown that the latent track has complicated structure and consists of different areas. For Xe-irradiated PET-sample 3 areas (with diameters 7, 17 and 50– 150 nm ) were found. Such track structure allows to explain the discrepancy between the data, previously obtained by using different methods.

UV- and γ-sensitization of latent tracks in polyethylene terephthalate

Photosensitization of polymer polyethylene terephthalate (PET) bombarded with swift heavy ions (Xe) was studied. Ultraviolet (UV)- and γ-irradiation were used for sensitization. Infrared spectroscopy (IR) and reversed-phase high-performance liquid chromatography (HPLC) were used to study the radiolysis products in latent tracks (directly in the sample or in the etching solution). It was found that the exposure of the sample to ultraviolet light results in the transformation of the radiolysis products formed in the tracks into terephthalic acid. Surface defects, detected by AFM, were found to correspond to tracks; their form (cavities and hillocks) and size changing reflect the changing of latent track state. It was found that UV irradiation destroyed the cross-linked regions in the tracks. This process (photodecomposition) was shown to be the key stage of the UV sensitization and the main cause of etching rate increase. The γ-irradiation effect on track etching was found to be almost the same.

Protein and Dye Adsorption on Poly(ethylene terephthalate) Nucleopore Membranes Modified with Polymers

Adsorption of basic, neutral, and acidic proteins on poly(ethylene terephthalate) nucleopore membranes was studied as a function of solution pH. Higher adsorption values were observed for basic and neutral proteins and lower, for acidic proteins. The value of pH corresponding to maximal adsorption was somewhat lower than the isoelectric points of proteins, thus suggesting that the adsorption was governed by a combination of ionic and hydrophobic interactions between proteins and the membrane surface. Proteins were adsorbed in an associated form. Membrane surface was modified with poly(ethylene imine) and poly(ethylene glycol). Combined modification of the membranes with these polymers was found to substantially decrease the adsorption of basic and neutral proteins, as well as basic dye and to slightly increase the adsorption of acidic proteins. The modifying coating had a high hydrolytic stability.

The track membrane porous structure and selective properties investigation

Abstract The difference between track membrane pore diameter values, obtained with methods of “bubble point” ( D BP ), hydrodynamics ( D HD ) and scanning electron microscopy ( D SEM ), was investigated. It was found that D SEM > D HD > D BP and this relation is significant for small pore. This phenomenon is explained on the basis of “double-cone” pore shape. The equation was derived, which presented a relation between these values. The results of calculation were compared with experimental results. The dependence of track membranes tested selectivity on particle size-to-pore size relation was obtained in experiment on latex particles filtration. It was shown, that this dependence is effected by the pore diameter calculation method.

Electrosurface and structural properties of poly(ethylene terephthalate) track membranes

The electrosurface characteristics are studied for poly(ethylene terephthalate) (PET) track membranes (TMs) with pore radii of 6.5–60 nm, which are used for ultra- and microfiltration. The data obtained enable one to indirectly assess the structure of tracks and variations in the pore space structure of TMs with an increase in the pore radii. Higher porosity values obtained for TMs from the data on their electrical resistance in comparison with those derived from the filtration data lead one to state that the PET pore surface has a loose structure. The thermal treatment of TMs makes the porosity values determined by the methods of electrical resistance and filtration closer to one another. The regularities of variations in the isoelectric point, ζ potential, and surface charge suggest that the properties and structure of PET pore surface depend on the pore radius. The data obtained may be used to predict the separating power of TMs.

Electrophysical properties of latent tracks of heavy ions in polymers

Poly(ethylene terephthalate) films irradiated by high-energy ions without additional etching have been studied. It has been shown that tracks of heavy high-energy ions in poly(ethylene terephthalate) may be considered to be single through capillaries suitable for studying electrophysical properties. It has been revealed that the surface electrical conductivities of electrolyte solutions (KCl, LiCl, MgCl2, and BaCl2) in the tracks of nonetched membranes are substantially higher, while the surface charges are noticeably lower, than those of etched membranes.

Influence of thermal treatment on electrosurface and structural properties of poly(ethylene terephthalate) track membranes

Electrosurface characteristics of polyethyleneterephthalate (PET) track membranes (TMs) with a pore radius of 6.5 to 60 nm used for ultra- and microfiltration have been studied. The results allow for indirect judgments on the track structure and variation in the pore space structure of TMs with the increasing pore radius. Higher values of TM porosity determined from data of the membrane electrical resistance compared with the porosity values obtained from the filtration data suggest that the PET pore surface has a loose structure. The thermal treatment of TMs makes the porosity values determined from the electrical resistance and filtration data closer to one another. The character of changes in the isoelectric point, ζ potential, and surface charge (σ) indicate that the properties and structure of the PET pore surface depend on the pore radius. The results obtained can be used to predict the separation power of TMs.

Pore formation in polyimide irradiated by high-energy ions and the properties of the obtained membranes

The optimum conditions are determined for etching latent Kr tracks in sodium hypochlorite solution to prepare polyimide track membranes (PI-TMs) with cylindrical pores and the electrosurface properties of the membranes are investigated. The stability of the porous structure of PI-TMs is studied at elevated temperatures (up to 250°C) in aggressive media (pH 1–12). It is shown that the porous structure of PI-TMs is characterized by enhanced chemical and thermal stability.

Application of track-etched membranes to synthesis of microcrystalline dielectric structures

The formation of oriented nanostructures of iodic acid (HIO3) on track-etched membranes has been studied. The study has shown that the method of forced filtration of supersaturated crystallization solutions through track membrane pores can be used to grow needlelike faceted microcrystals that have the cross size and preferential growth direction corresponding to those of the pores.

Structural and electric surface characteristics of heavy ion tracks in poly(ethylene terephthalate) and mica

The entry of high-energy Kr, Xe, and Bi ions into the surface of poly(ethylene terephthalate) (PET) and mica has been imaged. It has been shown that the track images have the shape of protuberances in both cases. The formation of protuberances is associated with the degradation of the material in the track region, in the formation of an amorphous structure, and the release of low-molecular radiolysis products as gaseous compounds. Holding the irradiated PET samples in water and dilute alkaline solution for several hours changes the surface topography due to hydrolysis of the material and escape of the radiolysis products to the solution. The kinetics of track etching in the dilute alkaline solution and pore formation have been studied. The electrical resistance and the permeability of the tracks in KCl, LiCl, MgCl2, and BaCl2 electrolytes have been measured.