Modification of properties of polymer membranes by low-temperature plasma treatment

The results of investigations into the use of low-temperature plasma for modification of porous polymer membranes are summarized. The basic lines of research in this area are considered. It is shown that plasma treatment is a quite effective tool for both improving the properties of existing polymer membranes and manufacturing new composite membranes with unique characteristics.     

Percolation of carbon nanomaterials for high-k polymer nanocomposites

This review summarized the recent progress towards high-k polymer composites bases on the near-percolated networks of carbon nanomaterials by focusing on the effects of distinct network morphologies on the dielectric properties. It is expected to give guidance on designing new near-percolated networks in polymer matrices towards next-generation polymer dielectrics.     

Modification of polyether ether ketone by low-temperature plasma and ion implantation method for use in medicine and biology

Russian Chemical Bulletin - The review concerns modification of polyether ether ketone (PEEK) using low-temperature plasma and ion implantation and presents the results of studies on the surface...     

Modification of ultra-high-molecular-weight polyethylene fibers and powders using low-temperature plasma

Literature data on the surface modification of ultra-high-molecular-weight polyethylene as fibers and powder under the influence of low-temperature plasma are analyzed. The change in polymer chemical composition and structure is described. The results of the studies, indicating a significant improvement in the contact and adhesion characteristics of the modified polymer and composite materials, are discussed.     

Modification of ultrahigh-molecular-weight polyethylene by low-temperature plasma (review)

Published data appeared in the last decade on the modification of ultrahigh-molecular-weight polyethylene (UHMWPE) films and plates with the use of low-temperature plasma are considered. Setups for sample processing by discharges of various types and methods for studying the changes occurring on the polymer surface are described. The results of the examination of contact, adhesion, strength, and tribological properties are presented. Changes in the chemical composition and structure of UHMWPE films are discussed, and data on the metabolic activity of the modified films are presented.     

Advanced functional polymer nanocomposites and their use in water ultra-purification

The application of nanotechnology has become inevitable in almost all sectors such as pharmaceuticals, food and beverages, electronics, transport, etc. The continuous development in the area has led to the emergence of the polymer nanocomposites. The polymer nanocomposites due to their improved mechanical, thermal, electrical, optical, and magnetic properties are widely used in various fields and slowly they have become an integral part of our life. As the application of polymer nanocomposite is going to be inexorable in the near future, this review aims to provide some insight on the need for the polymer nanocomposites, their basic classification, and their manufacturing methods. The study also outlines the analyses that are required to characterize the polymer nanocomposites. Further, the study discusses the existing application of polymer nanocomposites in various fields. As the polymer nanocomposites are going to play a major role in the field of waste water treatment for the years to come, the study has also attempted to shed some light on the application of nanocomposites in water purification.     

Investigation of sorption properties of carbon treated with low-temperature plasma

Plasma based technology for producing active carbon is proposed.     

Multiwalled carbon nanotube/polymer nanocomposites: Processing and properties

Nanocomposite materials were prepared with an amorphous poly(styrene‐co‐butyl acrylate) latex as a matrix with multiwalled carbon nanotubes (MWNTs) as fillers. The microstructure of the related films was observed by transmission electron microscopy, which showed that a good dispersion of MWNTs within the matrix was obtained. The linear and nonlinear mechanical behavior and the electrical properties were analyzed. Mechanical characterization showed a mechanical reinforcement effect of the MWNTs with a relatively small decrease of the elongation at break. The composite materials exhibited an elastic behavior with increasing temperature, although the matrix alone became viscous under the same conditions. The electrical conductivity of the composite filled with 3 vol % MWNTs was studied during a tensile test, which highlighted the late damage of the material. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1186–1197, 2005     

Modification of polymer surfaces by two-step plasma sensitized reactions

New reaction products have been generated on polyethylene and polystyrene surfaces using a novel two-step process. The first stage involves exposure to a downstream nitrogen plasma, and the second to either ozone or a corona discharge. It is observed that each of the two-step reactions yields very different reaction products, with an apparent increase in the formation of C? O functional groups in the former case and the formation of surface ? NO₂ groups in the latter case.     

Fabrication of super-macroporous nanocomposites by deposition of carbon nanotubes onto polymer cryogels

Electrically conducting super-macroporous carbon nanotube/polymer cryogel nanocomposites were fabricated by a novel approach based on deposition of carbon nanotubes (CNTs) onto the inner surface of pre-formed cryogels assisted by cryogenic treatment. Stable aqueous dispersions of multi-walled and single-walled carbon nanotubes were firstly obtained by non-covalent modification of pristine nanotubes with either pyrene containing polydimethylacrylamide or poly(ethylene oxide)₂₆-b-poly(propylene oxide)₄₀-b-poly(ethylene oxide)₂₆ copolymers and, then, exploited for the preparation of nanocomposites. The mechanical and electrical properties of nanocomposite materials were measured and compared to similar materials prepared by established method. The novel approach provided super-macroporous nanocomposites with high electrical conductivity (>10^?2 S/m) at much lower nanotube content (0.12 wt.%).     

The electronic role of DNA-functionalized carbon nanotubes: efficacy for in situ polymerization of conducting polymer nanocomposites

We have found that the polymerization process was 4,500 times faster when a self-doped polyaniline nanocomposite was fabricated using in situ polymerization in the presence of single-stranded DNA-dispersed and -functionalized single-walled carbon nanotubes (ssDNA-SWNTs). More importantly, the quality of the composite was significantly improved: fewer short oligomers were produced, and the self-doped polyaniline backbone had a longer conjugation length and existed in the more stable and conductive emeraldine state. The functionality of the boronic acid group in the composite and the highly improved electronic performance may lead to broad applications of the composite in flexible electronic devices. Blending of preformed polymer with carbon nanotubes is straightforward and widely used to fabricate nanocomposites. We demonstrate that this simple mixing approach might not fully and synergistically combine the merits of each individual component. Surprisingly, these advantages also cannot be obtained using in situ polymerization with preoxidized ssDNA-SWNTs, which is renowned as the "seed" method for production of conducting-polymer nanowires. The electronic structures of the carbon nanotubes and the monomer-nanotube interaction during polymerization greatly impact the kinetics of nanocomposite fabrication and the electronic performance of the resulting composites.     

Modification of unsaturated rubbers in low-temperature plasma as a method to improve their adhesion properties

The change in the contact-surface properties of the films of unsaturated rubbers under the effect of a direct-current discharge has been investigated in case of the placement of the samples at the anode. It has been demonstrated that the modification in plasma leads to a substantial improvement in the contact properties of rubber films.     

The mechanism of formation of polymer films from heptane in a low-temperature,low-pressure plasma

Calculations of the apparent activation energy for the growth of macromolecular entities in the form of cones on the surface of a growing film, as well as the apparent activation energy for the interaction of free radicals of the film with air oxygen after exposure of the film to the atmosphere, confirmed the existence of three steps of the formation of polymer films from heptane in a low-temperature, low-pressure plasma. It was found that the cones have a structure other than that of the film on which they are formed.     

An experimental investigation on the conductive behavior of carbon nanotube-reinforced natural polymer nanocomposites

It is well known that carbon nanotubes (CNTs) have excellent electrical properties and can be used as the nanofiller in natural polymers to produce conductive CNT/polymer nanocomposites. In this study, the conductive behavior of CNT-reinforced natural polymer nanocomposites was investigated. The effect of CNT concentration on the conductivity of CNT/natural polymer nanocomposites was also investigated. The natural polymers used were plasticized starch (PS) and chitosan (CS). FTIR spectroscopy was used to examine the interactions between PS, CS, and CNTs. TEM analysis on both nanocomposites were made to study the dispersion states of CNTs in both polymers. The results showed that the surface resistivities of both CNT/PS and CNT/CS nanocomposites decreased steeply with increasing CNT concentration. Particularly, the CNT/CS nanocomposites showed a better conductivity than the CNT/PS composites at the same CNT concentration. The TEM result showed that CNT/CS nanocomposites had better dispersibility and formation of fully connected, three-dimensional network structures between the CNTs than the CNT/PS nanocomposites, which results in the superior conductive property of CNT/CS nanocomposites compared to the CNT/PS nanocomposites.     

Altered phase model for polymer clay nanocomposites

This paper describes a multiscale approach used to model polymer clay nanocomposites (PCNs) based on a new altered phase concept. Constant-force steered molecular dynamics (SMD) is used to evaluate nanomechanical properties of the constituents of intercalated clay units in PCNs, which were used in the finite element model. Atomic force microscopy and nanoindentation techniques provided additional input to the finite element method (FEM) model. FEM is used to construct a representative PCN model that simulates the composite response of intercalated clay units and the surrounding polymer matrix. From our simulations we conclude that, in order to accurately predict mechanical response of PCNs, it is necessary to take into account the molecular-level interactions between constituents of PCN, which are responsible for the enhanced nanomechanical properties of PCNs. This conclusion is supported by our previous finding that there is a change in crystallinity of polymeric phase due to the influence of intercalated clay units. The extent of altered polymeric phase is obtained from observations of a zone of the altered polymeric phase surrounding intercalated clay units in the "phase image" of PCN surface, obtained using an atomic force microscope (AFM). An accurate FEM model of PCN is constructed that incorporates the zone of the altered polymer. This model is used to estimate elastic modulus of the altered polymer. The estimated elastic modulus for the altered polymer is 4 to 5 times greater than that of pure polymer. This study indicates that it is necessary to take into account molecular interactions between constituents in nanocomposites due to the presence of altered phases, and furthermore provides us with a new direction for the modeling and design of nanocomposites.     

The use of surfactants for dispersing carbon nanotubes and graphene to make conductive nanocomposites

Applications of composites based on carbon nanotubes and graphene require their exfoliation and dispersion in a polymer matrix. One of the main approaches to disperse and exfoliate carbon nanotubes and graphene is based on the use of surfactants. Here we review the surfactants utilized for dispersing carbon nanotubes and graphene, the mechanisms of filler stabilization and the methods for composite preparation based on the use of surfactants to get conductive polymer composites with minimum nanofiller loading.     

Heterogeneous initiators for the synthesis of polymer nanocomposites

Nanocomposites are obtained by the radical polymerization of styrene and methyl methacrylate on the surface of a dispersed filler containing chemisorbed compounds of quaternary ammonium, which catalyze decomposition of cumene hydroperoxide. The heterogeneous catalysts of hydroperoxide decomposition are obtained via the adsorption of cetyltrimethyl ammonium bromide and acetylcholine chloride on sodium montmorillonite, cellulose, and chitosan. The highest rate of the polymerization of both monomers is provided by the cellulose–cetyltrimethyl ammonium bromide catalyst. For a more hydrophilic methyl methacrylate, the rate of radical initiation is significantly lower at the same concentrations of the catalyst and hydroperoxide compared with hydrophobic styrene; however, the rate of polymerization is higher than for styrene because of a higher activity of methyl methacrylate in chain-propagation reactions. Relatively high rates of radical generation upon contact of cellulose–cetyltrimethyl ammonium bromide and cellulose–acetylcholine with hydroperoxides open the possibility to create cellulose-based disinfecting and medical materials.     

Methane conversion in low-temperature plasma

The conversion of methane in electric discharges of different types and under electron beam irradiation are considered. The influence of nonequilibrium conditions of conversion in low-temperature plasma on the energy consumption, product composition, and selectivity is analyzed. The results of works on plasma pyrolysis, partial plasma oxidation, and steam and carbon dioxide reforming of methane in a low-temperature plasma are discussed. It is shown that the use of chain processes makes it possible to substantially reduce the power consumption for methane conversion by an electrophysical device.