Hydrocarbon Plasma Polymer Research Articles

Convex vs concave surface nano-curvature of Ta2O5 thin films for tailoring the osteoblast adhesion

In certain medical interventions, temporally introduced bone implants are required to exhibit high biocompatibility, yet combined with low osseointegration, to allow for their easy removal afterwards. In this work, Ta2O5 surfaces are developed with good biocompatibility and with the osteoblast adhesion regulated by the nano-topography. The surfaces with convex nano-curvature are produced by applying reactive magnetron sputtering of tantalum over sub-monolayers of hydrocarbon plasma polymer particles. Subsequent ultrasonication leads to the removal of the particles from the coatings and results in the formation of the surfaces with concave nano-curvature. Primary human osteoblasts are found to sustain the viability and the mineralization ability on all kinds of these surfaces; however, Ta2O5 with the concave topography shows restrained adhesion of the cells. The limited cell adhesion is associated with a closed nature of the concave cavities which poses additional potential barriers for protein-mediated cell-surface interactions.

Improvement in the moisture barrier properties and flexibility by reducing hydrogen dangling bonds in SiNx thin films with plasma surface treatment

In this study, silicon nitride (SiNx) thin films were deposited by inductively coupled plasma chemical vapor deposition using trisilylamine (TSA, N(SiH3)3) and ammonia (NH3) plasma, and their moisture barrier properties were improved by plasma post-treatment. Ar, N2, and O2 plasmas were applied to the SiNx films after deposition. After O2 plasma treatment, the reduction of hydrogen in -NHx was confirmed by FT-IR analysis. Mass spectroscopic results showed a distinct hydrogen peak in the O2 plasma processes. Hydrogen was speculated to be removed from the SiNx surface, and the reduced hydrogen on the surface was attributed to the densification of the SiNx thin films. The increased film density reduced the moisture permeability of the SiNx thin films. The water vapor transmission rate (WVTR) of 120-nm thick single SiNx thin films was reduced by 77% to 3.0 × 10−3 g/m2-day from 1.3 × 10−2 g/m2-day with O2 plasma treatment. The increase of WVTR evaluated using a bending test was adopted to estimate flexibility. The increase of WVTR reduced to 71% in O2-plasma treated SiNx single layers from 88% with untreated SiNx single layers after bending the film at a bending radius of 1.5 cm. Multilayer moisture barrier films were fabricated using the O2-plasma treated SiNx layers and hydrocarbon plasma polymer layers made of cyclohexane plasma to further improve the moisture barrier properties and flexibility. The increase of WVTR reduced by approximately five times in the multilayer structure with O2 plasma treated SiNx/hydrocarbon plasma polymer after the bending test. A WVTR of 7.6 × 10−4 g/m2-day was obtained with an alternating nine-layer structure. In this study, we demonstrated that plasma post-treatment processes can improve the moisture barrier properties and flexibility by reducing the hydrogen dangling bonds and hydrogen concentration inside SiNx thin films.

Advances and challenges in the field of plasma polymer nanoparticles.

This contribution reviews plasma polymer nanoparticles produced by gas aggregation cluster sources either via plasma polymerization of volatile monomers or via radio frequency (RF) magnetron sputtering of conventional polymers. The formation of hydrocarbon, fluorocarbon, silicon- and nitrogen-containing plasma polymer nanoparticles as well as core@shell nanoparticles based on plasma polymers is discussed with a focus on the development of novel nanostructured surfaces.

The study of creation of polymerizable species in radio frequency hydrocarbon plasma polymerization in a closed reactor system

The study of radio frequency glow discharge of saturated hydrocarbon monomer indicated that the glow forms distinctive glow in plasma polymerization systems. The radio-frequency ethane plasma polymerization in a closed reactor system was studied. The composition of reactive species in the luminous gas phase was monitored during the deposition process by optical emission spectroscopy. Optical emission analysis indicates that polymerizable species are mainly formed in the glow region. It was found that, in such a closed plasma system, the deposition of ethane plasma polymers could be visualized as the batch processes. In the early stage of radio-frequency plasma initiation, the deposition of plasma polymers was dominated by the hydrocarbon-based species because the hydrocarbon-based species polymerized much quicker than hydrogen-based species. In the final stage, because of the exhaustion of all polymerizable species in the system, the deposition terminated and the deposited plasma polymer surface was endlessly treated by nonpolymer forming gas plasma. The growth of radio frequency plasma polymerized hydrocarbon film clearly showed the dominating effects of luminous gas phases on the polymerizable tendency in plasma polymerization system.

Plasma Polymerization on Mesoporous Surfaces: n-Hexane on Titanium Nanoparticles

Plasma treatment of porous materials has huge potential in many applications where chemical modification of interior structure or its loading with polymeric matrices is required. Plasma polymers are often assumed to grow conformally on solid supports; however, their innate roughness may interfere with the surface topography at mesoscale. Here, model mesoporous coatings were prepared by deposition of titanium nanoparticles with the average size of 50 nm onto flat silicon substrates. The nanoparticles were fabricated by magnetron sputtering in the configuration of a gas aggregation source. The porous coatings were subsequently subjected to deposition of soft hydrocarbon plasma polymers from n-hexane. In the early stage of the deposition, negligible increase of thickness is observed as the plasma polymer fills the inner free space of the coatings. The topographical features expand in lateral dimension, but the RMS roughness does not change. In the late growth regime, the inner voids become filled and the plasma polymer grows on top of the coatings. The growth proceeds with preferential filling of the valleys between the surface asperities, thus leading to smoothening of the surface. The decrease of roughness is manifested in negative growth exponent. Equality between the absolute values of the local and global roughness exponent evidences about self-affine growth dynamics. Nevertheless, the set of the critical exponents (the growth exponent β = −0.16, the dynamic exponent 1/z = 0.16, the roughness exponent |α| = 1.0) indicates that the deposition does not match any of universality classes of local growth. Local diffusion coupled with nonlocal mass transport due to re-emission of the incoming species can explain the kinetic smoothening observed. The technology allows for fabrication of mesoporous coatings with precisely adjustable pore size or straightforward production of nanocomposite thin films with nanoparticles homogeneously embedded in the matrix of plasma polymer.

Effect of various concentrations of Ti in hydrocarbon plasma polymer films on the adhesion, proliferation and differentiation of human osteoblast-like MG-63 cells

Hydrocarbon polymer films (ppCH) enriched with various concentrations of titanium were deposited on microscopic glass slides by magnetron sputtering from a Ti target. The maximum concentration of Ti (about 20at.%) was achieved in a pure argon atmosphere. The concentration of Ti decreased rapidly after n-hexane vapors were introduced into the plasma discharge, and reached zero values at n-hexane flow of 0.66sccm. The decrease in Ti concentration was associated with decreasing oxygen and titanium carbide concentration in the films, decreasing wettability (the water drop contact angle increased from 20° to 91°) and decreasing root-mean-square roughness (from 3.3nm to 1.0nm). The human osteoblast-like MG-63 cells cultured on pure ppCH films and on films with 20at.% of Ti showed relatively high concentrations of ICAM-1, a marker of cell immune activation. Lower concentrations of Ti (mainly 5at.%) improved cell adhesion and osteogenic differentiation, as revealed by higher concentrations of talin, vinculin and osteocalcin. Higher Ti concentrations (15at.%) supported cell growth, as indicated by the highest final cell population densities on day 7 after seeding. Thus, enrichment of ppCH films with appropriate concentrations of Ti makes these films more suitable for potential coatings of bone implants.

Direct covalent coupling of proteins to nanostructured plasma polymers: a route to tunable cell adhesion

Flat and nanostructured thin films were fabricated by deposition of ultra-thin (<2nm) layer of hydrocarbon plasma polymer over polished silicon and over a pattern of 8nm-thick poly(ethylene) islands on silicon. Linker-free radical-based covalent binding of bovine serum albumin and tropoelastin was confirmed for both types of films. The binding capability of albumin was found to be stable over many days of ambient air storage time. Tropoelastin-mediated flat plasma polymers favored adhesion and proliferation of osteoblast-like MG-63 cells. Nanostructured plasma polymers were multi-affine and their hierarchical surface represented an additional barrier for cell attachment.

Properties of a-C:H:O plasma polymer films deposited from acetone vapors

To gain insight into the deposition and stability of oxygen-containing plasma polymer films, the properties of amorphous oxygenated hydrocarbon (a-C:H:O) plasma polymer coatings deposited from acetone vapors under various experimental conditions are investigated. Apart from the discharge power, the influence of the reactive carbon dioxide (CO2) gas on the structure of the resulting films is studied. It is found by characterization using X-ray Photoelectron Spectroscopy and Fourier-Transform Infrared Spectroscopy that the experimental conditions particularly influence the amount of oxygen in the deposited a-C:H:O plasma polymer films. The O/C elemental ratio increases with increasing amount of CO2 in the working gas mixture (up to 0.2 for 24sccm of CO2 at 30W) and decreases with increasing RF discharge power (down to 0.17 for 50W). Furthermore, the nature of bonds between the oxygen and carbon atoms has been examined. Only low amounts of double and triple bonded carbon are observed. This has a particular influence on the aging of the plasma polymer films which is studied both in ambient air and in distilled water for up to 4months. Overall, stable a-C:H:O plasma polymer films are deposited comprising low amounts (up to about 5%) of ester/carboxyl groups.

Deposition of Al nanoparticles and their nanocomposites using a gas aggregation cluster source

The study describes the preparation and properties of Al/Al x O y nanoparticles and their nanocomposites with hydrocarbon plasma polymer. The nanoparticles were deposited using a simple gas aggregation cluster source based on a planar magnetron. The influence of deposition parameters on size distribution was studied. It was found that Al nanoparticles may be deposited with mean diameter ranging from 30 to 60 nm by varying magnetron current from 0.4 to 0.2 A. Attention was also paid to the investigation of the charge of the nanoparticles. It is shown that a large portion of Al x O y nanoparticles leave the gas aggregation source as negatively charged. The nanoparticles were also embedded into the plasma polymer matrix by their simultaneous co-deposition with plasma-polymerized n-hexane. Morphology and chemical composition of such fabricated nanocomposites were determined. It was shown that Al x O y nanoparticles embedded into the polymeric matrix exhibit localized surface plasmon resonances in the deep ultraviolet region of the electromagnetic spectrum and the position of the plasmon peak is strongly correlated with nanoparticle size.

Tailor-Made Silver Release Properties of Silver-Containing Functional Plasma Polymer Coatings Adjusted Through a Macroscopic Kinetics Approach

Combining a functional plasma polymer matrix with antibacterially active silver (Ag) within a nanocomposite structure allows secure production and applications in various fields, especially in the medical sector. Therefore, nitrogen or oxygen containing hydrocarbon plasma polymers and Ag nanoparticles were simultaneously deposited. Functional groups such as amino or carboxylic groups as well as an adjusted amount of Ag can be incorporated into the growing films by controlling the plasma deposition properties. For this purpose, macroscopic kinetics were used to characterise the deposition behaviour also as a base for possible industrial up-scaling. XPS and ICP-OES were used to analyse the chemical composition of the polymer–Ag nanocomposites and the Ag content which could be incorporated depending on the plasma process conditions. Finally, the Ag release was determined in bi-distilled water for classification and comparison with the antibacterial properties. The antibacterial effect of the polymer–Ag nanocomposites was proofed with the gram− strain Pseudomonas aeruginosa PAO1 and the gram+ strain Staphylococcus aureus (ST12 Group) showing a clear efficacy dependence on the amount of released Ag and the possibility for tailor-made antibacterial active plasma films.

Adhesion, Growth and Differentiation of Osteoblasts on Surface-Modified Materials Developed for Bone Implants

This review briefly outlines the history and possibilities of bone reconstruction using various types of artificial materials, which allow interaction with cells only on the surface of the implant or enable ingrowth of cells inside the material. Information is also provided on the most important properties of bone cells taking part in bone tissue development, and on diseases and regeneration. The most common cell types used for testing cell-material interaction in vitro are listed, and the most commonly used approaches to this testing are also mentioned. A considerable part of this review is dedicated to the physical and chemical properties of the material surface, which are decisive for the cell-material interaction, and also to modifications to the surface of the material aimed at integrating it better with the surrounding bone tissue. Special attention is paid to the effects of nanoscale and microscale surface roughness on cell behaviour, to material surface patterning, which allows regionally-selective adhesion and growth of cells, and also to the surface chemistry. In addition, coating the materials with bioactive layers is examined, particularly those created by deposition of fullerenes, hybrid metal-fullerene composites, carbon nanotubes, nanocrystalline diamond films, diamond-like carbon, and nanocomposite hydrocarbon plasma polymer films enriched with metals.

Nanocomposites and nanostructures based on plasma polymers

Nanocomposite metal/plasma polymer films have been deposited since the seventies of the last century using sputtering or thermal evaporation of a metal simultaneously with a plasma polymerization process. The main attention was paid to fluorocarbon and hydrocarbon plasma polymers as matrices for the incorporation of metals such as Au and Ag. Main deposition techniques used for the fabrication of such nanocomposites are reviewed together with an overview of their basic optical and electrical properties, composition and structure. Proposed applications are mentioned as well. In addition, RF magnetron co-sputtering of a polymer such as polytetrafluoroethylene, is also mentioned. Nanostructuring of a fluorocarbon plasma polymer by changing deposition parameters including deposition system geometry is revealed and the application in terms of superhydrophobic coating is mentioned. Cluster sources, namely the gas aggregation (condensation) cluster source (GAS) based on a planar magnetron in a compact and simple form is described and its performance for the preparation of nanocomposite and nanostructured metal/plasma polymer films is discussed.

Plasma Process. Polym. 1/2010

Cover: Heterogeneous nanoscale columns of titanium and hydrocarbon plasma polymer are prepared by magnetron sputtering using glancing angle deposition (GLAD). The flux ratio between Ti atoms and hydrocarbon species is the key parameter influencing morphology and chemical composition of such structures. Further details can be found in the article by A. Choukourov,* P. Solar, O. Polonskyi, J. Hanus, M. Drabik, O. Kylian, E. Pavlova, D. Slavinska, and H. Biederman on page 25.

Influence of the luminous gas phase on direct current plasma polymerized hydrocarbon film growth

The characteristics of the glow created in plasma polymerization systems are notably different from inert gas plasmas such as argon, in which the well-known negative glow is the primary glow. The study of direct current (DC) glow discharges of a series of saturated hydrocarbon monomers indicated that cathode glow forms the distinctive glow in plasma polymerization systems. It forms a strong contrast to characteristic negative ionization glow of glow discharges of inert gases that do not polymerize. Optical emission analysis results obtained from these plasma deposition systems indicated that polymerizable species are mainly formed in cathode glow region. The growth of direct current plasma polymerized hydrocarbon film clearly showed the dominating effects of luminous gas phases on the polymerizable tendency in plasma polymerization system.

NMR Study of Polyethylene‐Like Plasma Polymer Films

AbstractThermal decomposition (“evaporation”) of polyethylene (PE) was performed with or without an activation of volatile fragments in an rf glow discharge. Study of the deposition process via quadrupole mass spectrometry showed the presence of hydrocarbon fragments up to 100 amu. Properties of the resulting films were investigated by means of FTIR, XPS, and NMR spectroscopy. These analyses showed that the activation of polymeric fragments in plasma enhances cross‐linking and the films become hydrocarbon plasma polymers. However, these plasma polymers resemble much more the original PE. In addition, NMR technique enabled to assess the ratio of crystalline and amorphous phases in the films.

Influence of RF Plasma Reactor Setup on Carboxylated Hydrocarbon Coatings

AbstractFunctional hydrocarbon plasma polymer coatings were investigated using a low pressure RF plasma reactor. The deposition rate was examined for different CO2/C2H4 gas ratios and different power inputs at constant pressure. The CO2/C2H4 ratio can be used to tailor the functionality and the permanence of the plasma polymer coatings which is shown by XPS. The deposition of these plasma polymer coatings was compared in a symmetrical and asymmetrical setup of the reactor and discussed regarding energy input and plasma sheath potential for the varying plasma conditions. Furthermore, the influence of Ar admixture was examined in order to identify sputtering conditions by using an asymmetric Ag electrode. While a drop in the absolute deposition rate can be seen for Ar added in symmetrical conditions, the asymmetrical setup showed no noticeable differences.magnified image

Dust plasma analogue for interstellar 217.5 nm extinction

The new ultraviolet (UV) extinction measurements of carbonaceous nanoparticles in the range from 140 nm to 260 nm are presented. The plasma polymerized hydrocarbon nanoparticles were already proposed as a new astro analogue, which describe the infrared (IR) extinction spectra in an excellent way. We use the same particles to find the possible carrier of the 'mysterious' UV 217.5 nm extinction 'bump' of interstellar media (ISM).

Composite TiOx/Hydrocarbon Plasma Polymer Films Prepared by Magnetron Sputtering of TiO2 and Poly(propylene)

This study describes the preparation and the properties of TiO x /hydrocarbon plasma polymer composite films. Films are prepared by simultaneous sputtering in argon from two balanced magnetrons equipped with TiO 2 and PP targets. The resulting films exhibit a wide range of properties in dependence on the preparation conditions - primarily on the ratio of the deposition rates r(TiO x )/r(PP) and thus the power delivered to the magnetrons. The deposition process is monitored by optical emission spectroscopy. The composition and morphology of the composite films have been analyzed by means of RBS/ERDA, FTIR, AFM, and TEM. Optical properties of the films are studied in the UV and visible range of the spectrum. Finally, an attempt has been made to express the amount of inorganic phase present in the organic matrix in terms of a filling factor.

Composite [formula omitted] plasma polymer films prepared by RF magnetron sputtering of SiO 2 and polyimide

Preparation procedure and properties of composite SiO x / hydrocarbon plasma polymer films are described and discussed. The composite films have been prepared by RF sputtering in argon from two balanced magnetrons equipped with silica (SiO 2) and polyimide (PI) targets. The films obtained reveal a wide range of properties which depend on the preparation conditions; primarily on the RF power delivered to the magnetrons. Morphology and composition of the composite films have been analysed by means of AFM, TEM, RBS/ERDA and FTIR. Wettability in terms of contact angle of water increases from 28 ∘ to 46 ∘ when the content of the SiO x component of the composite increases. Peculiar properties of the composite SiO x / hydrocarbon plasma polymer films are discussed with respect to their elemental composition and nature of chemical bonds created on the surface of the films. Finally, an attempt is made to express the amount of inorganic phase present in the organic matrix in terms of a filling factor.

Large area deposition of functional plasma polymers on polymer substrates

In this work we present a new plasma deposition apparatus developed for the effective plasma polymer deposition on polymeric substrates. It consists of a specially designed plasma reactor with a 60 MHz capacitively coupled electrode and an adapted substrate holder to implement roll-to-roll processes. Using siliconorganic precursors the high deposition rates required for industrial scale deposition on plastic films are achieved. The deposition mechanism is characterized by deposition rate as a function of power and monomer flow. Infrared spectroscopy investigation of the deposited thin films confirm the ability to include functional groups in siliconorganic and pure hydrocarbon plasma polymers in the 60 MHz plasma.