A. B. Gilman

Low-Temperature Plasma Treatment as an Effective Method for Surface Modification of Polymeric Materials

The specific features of the plasma modification process and its application area are considered. It is shown that this method is very effective for the enhancement of adhesive properties of a wide range of polymeric materials used in different fields of technology, as well as in the manufacture of membranes for different designations, including membranes for biological and medical purposes.

Polymer Composite Nanomembranes with Asymmetry of Conductivity

This paper describes a structure and electrotransport properties of poly(ethylene terephthalate) track membrane (PET TM) modified by plasma of thiophene. It is shown that the deposition of the polymer on the track membrane surface by plasma polymerization of thiophene in case of forming a semipermeable layer results in creation of composite nanomembrane having in electrolyte solutions of asymmetry of conductivity - a rectification effect. It is caused by presence in the membrane of two layers with various functional groups, and also by changing of the pore geometry. Such type membranes can be used for creation of chemical and biochemical sensors.

Modification of the Surface Layers of Fluoropolymer Films by DC Discharge for the Purpose of the Improvement of Adhesion Properties

The effect of dc discharge treatment at the anode and cathode on the surface properties of polytetrafluoroethylene (PTFE), tetrafluoroethylene–hexafluoropropylene copolymer (FEP) and poly(vinylidene fluoride) (PVDF) polymer films was studied. It was found that the modification of the films under conditions that ensure the separation of the discharge active species acting on the polymer materials makes it possible to achieve substantially lover values for the contact angle and higher values for the surface energy than in the case of other modes of discharge. The changes in the composition and structure of the films were studied by means of IR spectroscopy and electron spectroscopy for chemical analysis (ESCA). It was found that new oxygen-containing groups are formed on the polymer surface as a result of dc discharge treatment. To appreciate the adhesion characteristics of fluoropolymer films modified by dc discharge, American Society for Testing and Materials Standard Test Method for Measuring Adhesion by Tape Test (ASTM D3359-02) was used. The adhesion tape Scotch 810 and vacuum metallization of the film surface are account for the basis of this method. It was found that the adhesive bonding strength of the plasma treated films substantially increased.

Charging of Polycarbonate Films in a Direct-Current Discharge

The effect of treatment of Diflon, Makrolon®, and Lexan® polycarbonate films in the cathode fall of a dc discharge was studied. Plasma treatment was shown to result in the hydrophilization of the film surface. The dependence of the contact angle on the discharge current and treatment time was examined. It was found that the discharge induced a negative charge on the polycarbonate surface. The surface-charge density was correlated with the contact angle for various treatment conditions. Space charging processes in glow discharge-treated films were investigated using the thermally stimulated relaxation and depolarization techniques. The role of produced charged entities in an increase in the surface energy of modified polycarbonate films was revealed.

Alteration in the surface properties of direct-current discharge-treated tetrafluoroethylene-ethylene copolymer films

A change in the contact properties of the surface of a tetrafluoroethylene-ethylene copolymer film by treatment of its samples mounted on the cathode and anode in a dc discharge has been studied. It has been shown that the modification leads to a significant improvement in the contact properties of the films owing to the appearance of oxygen-containing polar groups on the polymer surface. The formation of such groups has been proved by X-ray photoelectron spectroscopy. The peel strength of both the untreated and modified films was measured by the T-peel test method.

Modification of the chitosan structure and properties using high-energy chemistry methods

Literature on the modification of the natural polymer chitosan using high-energy chemistry methods (treatment by a low-temperature plasma, with an electron beam, energetic ions, or γ-iradiation) has been surveyed. The basic chitosan treatment procedures and facilities used in the processes have been described. The instrumental techniques used to study changes in the chemical structure and properties of modified chitosan have been considered. Data showing the possibility of using modified chitosan in medicine and biotechnology have been presented.

Low-Frequency Glow Discharge Treatment of Poly(ethylene terephthalate) Films

The alteration of surface characteristics of the PET-E poly(ethylene terephthalate) film by treatment in the cathode fall of an ac (50 Hz) glow-discharge plasma was studied. The plasma-assisted modification leads to surface hydrophilization which is retained for a long period of time. It was found that the discharge treatment induced a negative charge in the polymer surface layer. The charge density created under different treatment conditions was correlated with the contact angle. The thermally stimulated relaxation and depolarization measurements on the original and the modified film showed that charge buildup in the film during the discharge treatment was due to trapping of injected electrons. From the experimental data, it was inferred that the charge states emerged play the determining role in enhancing the surface energy of modified PET films.

The modification of polypropylene structure by low-frequency glow discharge

Abstract The modification of polypropylene (PP) was carried by low-frequency glow discharge in air (or nitrogen). The PP samples had been obtained with the heterogeneous catalytic system δ-TiCl3–AlEt2Cl in the presence of hydrogen and with the homogeneous system racE-t(Ind)2ZrCl2—methylalumoxane (MAO). It was shown that plasma treament results in considerable changes in the whole structure of PP. These changes manifest themselves in a great increase in molecular masses (MM) and melting temperatures (Tm) of the all investigated samples. However, structural modfification is especially great for PP synthesized with the metallocene system. In this case the molecular mass has increased approximately 10-fold and the melting temperature has risen from 130 to 164°C. Simultaneously, the fraction of isotactic pentads and the steroregularity parameters have increased. In the same case a drastic fall in the solubility of the polymer took place. So the fraction of the polymer insoluble in boiling heptane has increased from 7 to 96%, that is, PP has become highly isotactic. Before the treatment the crystalline structure of the above PP consisted of α- and γ-modifications. We have shown that plasma induces the transformation of the γ-form into the α-form. We believe that these changes in PP structure were caused by the UV component of the plasma radiation.

Modification of polymer membrane properties by low-temperature plasma

The results of investigations into the use of low-temperature plasma for modification of polymer membranes are considered. The basic lines of research in this area are highlighted. It is shown that plasma treatment is quite an effective tool for both improving properties of existing polymer membranes and manufacturing new composite membranes with unique characteristics. Examples of successful use of plasma-modified membranes in various branches of industry and medicine are given.

Micro- and nanofluidic diodes based on track-etched poly(ethylene terephthalate) membrane

The work is devoted to fabrication of micro- and nanofluidic diodes, devices that are polymer composite membranes with asymmetric conductivity. To this end, a polytetrafluoroethylene layer has been applied by electron beam sputter deposition on one side of a poly(ethylene terephthalate) track-etched membrane used as a porous substrate. It has been shown that the resulting effect of conductivity asymmetry is due to not only a significant decrease of the diameter of pores and a change in their geometry in the deposited polytetrafluoroethylene layer, but also the existence of an interface between the initial membrane and the hydrophobic polymer layer in the pores. Devices of this kind can be used for directional ion transport.