Formation of an adherent layer by DC plasma polymerization

The molecular structure of the interphase between plasma-polymerized acetylene films and steel substrates was determined using in situ reflection–absorption infrared spectroscopy (RAIR) and X-ray photoelectron spectroscopy (XPS). Plasma-polymerized acetylene films were deposited onto polished steel substrates using argon as a carrier gas and inductively coupled, radio frequency (RF)-powered plasma reactors that were interfaced directly to the XPS and Fourier transform infrared (FTIR) spectrometers. RAIR showed that the plasma polymerized films contained large numbers of methyl and methylene groups but only a small number of mono substituted acetylene groups, indicating that there was substantial rearrangement of the monomer molecules during plasma polymerization. Bands were observed near 1020 and 855 cm−1 in the RAIR spectra that were attributed to skeletal stretching vibrations in C–C–O–Fe groups, indicating that the plasma-polymerized films interacted with the substrate through formation of alkoxide bonds. Another band was observed near 1565 cm−1 and attributed to carboxylate groups in the interphase between the films and the oxidized surface of the substrate. Results obtained from XPS showed that the surface of the iron substrate consisted mostly of a mixture of Fe2O3 and FeOOH and that iron was mostly present in the Fe(III) oxidation state. However, during plasma polymerization of acetylene, there was a tendency for the concentration of FeOOH groups to decrease and for the concentration of Fe(II) to increase, due to the reducing nature of argon/acetylene plasmas. Results from XPS also confirmed the formation of alkoxide and carboxylate groups in the interphase during plasma polymerization of acetylene.

Radiofrequency (RF) plasma polymerization is a convenient thin film deposition process as it facilitates the synthesis of polymer films with stable physico-chemical properties suitable for various applications in microelectronic, optical, and biomedical fields. The unique properties of these plasma polymerized films as compared to the conventional ones are strongly related to the proper adjustment of the external plasma discharge parameters and selection of suitable monomer. It is also important to study the fundamental chemistry of RF plasma polymerization process, so that one can successfully correlate the internal features of the discharge with the film properties and explore their possible technological applications. The possibility of using styrene-based plasma polymer (SPP) films on bell metal as protective coatings is explored in this work. Depositions of the films are carried out in RF Ar/styrene discharge at working pressure of 1.2 × 10−1 mbar and at the RF power range of 20 to 110 W. Optical emission spectroscopy (OES) is used to study the active species generated during plasma polymerization, while Fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS) are used to analyze the internal chemical structures of the films. The protective performances of the SPP films are attempted to correlate with the results obtained from OES, FT-IR, and XPS analyses.

We have examined the dynamics of dust in collisionless and collisional electrode sheaths of dc and rf glow discharges. The charge of the dust particles, the various forces, oscillation frequencies, damping effects and energy potential extrema are calculated. In the rf sheaths the dust particle charge is negative in the whole sheath, while in the dc sheaths the dust particle charge is positive in a major part of the sheath. Collection of dust leads to changes in the dust and plasma potentials and to a reduction in the maximum dust particle size that can be levitated. Close to the electrode there will be a dust-free zone.

Surface modification of poly(tetrafluoroethylene) films by plasma polymerization and deposition of glycidyl methacrylate (GMA) was carried out. The effects of glow-discharge conditions on the chemical structure and composition of the deposited GMA polymer were analyzed by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy. XPS and FTIR results revealed that the epoxide groups in the plasma-polymerized GMA (pp-GMA) layer had been preserved to various extents, depending on the plasma deposition conditions. The morphology of the modified PTFE surface was investigated by atomic force microscopy (AFM). The pp-GMA film with well-preserved epoxide groups was used as an adhesion promotion layer to enhance the adhesion of the electrolessly deposited copper on the PTFE film. The T-peel adhesion test results showed that the adhesion strength between the electrolessly deposited copper and the pp-GMA-modified PTFE (pp-GMA-PTFE) film was much higher than that between the electrolessly deposited copper and the pristine or the Ar plasma-treated PTFE film. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3498–3509, 2000

Rapid re-endothelialization at an atherosclerotic lesion after stent employment is essential for reducing or preventing local thrombus formation and restenosis. To prevent these complications via enhanced rapid re-endothelialization, poly n-butyl methacrylate (PPBMA) coating was deposited on the stent surface through a radio-frequency plasma polymerization process, with oxygen as the carrier gas. Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) characterization confirmed the occurrence of the plasma polymerization and the chemistry properties of the PPBMA. Scanning electron microscopy (SEM) revealed a smooth and dense surface. The wettability of the polymeric films measured by the contact angle indicated that the surface was more hydrophilic (2.0 +/- 1 degrees ) than the original surface (24 +/- 1 degrees ) by the introduction of the PPBMA coating, with a slight decrease even after 4 days. The results of the culture of human umbilical cord veins endothelial cells (HUVEC) in vitro showed that compared with the control of 316L stainless steel, the attachment and growth of cells on the PPBMA-coated surface was significantly enhanced, and a confluent endothelial cells layer was formed after a 4-day culture. A platelet adhesion experiment revealed that the blood compatibility of the substrate surface after PPBMA deposition was also obviously improved. The PPBMA coating remained intact on the stent surface after expansion according to the clinic protocol, indicating that the adhesive strength of PPBMA coating was high enough to withstand the external force in the process of stent expansion. This in vitro pilot study prior to in vivo experiments suggested that this plasma PPBMA was promising for coating stent materials for rapid re-endothelialization.

A study on the plasma polymer thin film surface modification for DNA alignment by using high energy electron beam irradiation

A novel plasma‐polymerized 1‐cyanoisoquinoline (PPCIQ) thin film of desired thickness was prepared by plasma polymerization under different glow discharge conditions. The effect of the discharge power on the chemical structure, surface composition and morphology of the PPCIQ thin films were investigated by Fourier Transform Infrared (FTIR) Spectroscopy, X‐ray Photoelectron Spectroscopy (XPS), Atomic Force Microscopy (AFM) and deposition rate measurements. A high retention of the aromatic ring structure of the starting monomer in the deposited plasma films is obtained at a low discharge power of 15 W. The plasma‐synthesized films are homogeneous and quite suitable for the measurement of dielectric properties. The dielectric measurements show that a low dielectric constant of 2.62 has been obtained for the PPCIQ thin films for the first time.magnified image

Plasma polymerized hexamethyldisiloxane (PP-HMDSO) thin films have been obtained in a DC glow discharge from oxygen/HMDSO gas mixtures. Such films are successfully applied to the pr otection of Al metallisations on plastic substrates. The composition of the films (SiO<SUB>x</SUB>C<SUB>y</SUB>:H) may be varied from organic (polymer-like) to inorganic (SiO<SUB>2</SUB>-like) by varying the oxygen-to-monomer ration in the precursor gas mixture. The structural and functional properties of the films are studied as a function of the plasma parameters.

Fluoropolymer films were deposited on the Ar plasma-pretreated Si(100) surfaces by plasma polymerization of perfluorohexane (PFH, a linear fluorocarbon), perfluoro(methylcyclohexane) (MCH, a cyclic fluorocarbon), and hexafluorobenzene (HFB, an aromatic fluorocarbon) under different glow discharge conditions. The effects of the radio-frequency plasma power on the chemical composition and structure of the plasma-polymerized fluoropolymer films were studied by x-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, time-of-flight secondary ion mass spectrometry, and water contact angle measurements. The changes in structure and composition of the three types of the plasma-deposited films from those of the respective fluorocarbons were compared. Under similar glow discharge conditions: (i) the extent of defluorination was highest for the PFH polymer, (ii) the deposition rate was highest for the HFB polymer, (iii) the cyclic structure of MCH was less well preserved than the aromatic structure of HFB, (iv) aliphatic structures appeared in the plasma-deposited MCH polymer, and (v) the plasma-polymerized HFB has the highest thermal stability due to the preservation of the aromatic rings. The adhesive tape peel test results revealed that the plasma-polymerized and deposited fluoropolymer layers were strongly bonded to the Ar plasma-pretreated Si(100) surfaces.

Continuous treatment of polyester/cotton blended fabric samples was carried with hexamethyldisiloxane (HMDSO) plasma on the pilot scale atmospheric pressure plasma reactor. The mixture of helium and argon was used as carrier gas for generating dielectric barrier discharge plasma. The effect of discharge power and treatment time on the water repellent properties of samples were evaluated with contact angle (CA) and spray test measurements. Spray test and CA results showed improved resistance to wetting with water. The effect of discharge conditions on the surface morphology and surface chemistry of plasma treated samples were investigated by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopic analysis, respectively. The presence of Si‐O‐Si and Si‐CH3groups in the structure of plasma polymer deposited at the surface of P/C samples was revealed by FTIR spectroscopy. Further, structural differences in HMDSO plasma polymer deposited under different discharge conditions were reported with reference to organic/inorganic nature of plasma polymer. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.

Summary: A novel conjugated polynitrile, plasma‐polymerized 1‐isoquinolinecarbonitrile (PPIQCN) was prepared by plasma polymerization for the first time. The structure and surface compositions of the deposited PPIQCN thin films were investigated by Fourier Transform Infrared (FTIR), UV‐Visible absorption and X‐ray Photoelectron Spectroscopy (XPS). The results show that extensively conjugated CN double bonds were formed in PPIQCN films during the plasma polymerization of 1‐isoquinolinecarbonitrile. An obvious red shift of more than 120 nm in the maximum absorption wavelength (λmax) for PPIQCN films as compared with the monomer absorption spectrum was observed. To check the possibility of applying the PPIQCN films as optical devices, photoluminescence (PL) measurements were also carried out and a maximum PL emission intensity was observed at about 458 nm.Photoluminescence spectrum of the PPIQCN18 thin film.magnified imagePhotoluminescence spectrum of the PPIQCN18 thin film.

The surface of magnesium oxysulfate (MOS) whiskers was treated through plasma polymerization to increase the compatibility between the MOS whiskers and a polymer matrix. Different plasma parameters were chosen to determine the most hydrophobic coating. The surface structure of the plasma‐treated MOS whiskers was examined. The MOS whiskers retained their crystal structure after plasma treatment, as shown by X‐ray powder diffraction (XRD) analyses. X‐ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FT‐IR) spectroscopy analyses revealed that a polymer sheath was formed on the surface of the MOS whiskers, and interfacial chemical bonds were generated between the polymer sheath and the MOS whiskers. The thin‐layer polymer sheath was uniform around the entire surface of the MOS whiskers and exhibited a typical amorphous structure, as determined by transmission electron microscopy (TEM) combined with selected area electron diffraction (SAED) analyses. The possible reaction mechanism on the surface of the MOS whiskers under plasma treatment was then proposed. Finally, the effect of surface treatment was evaluated by scanning electron microscopy (SEM), measurement of the contact angle and contact angle hysteresis, and torque rheometer. Results showed that plasma treatment could markedly increase the hydrophobicity of the MOS whiskers' surface, effectively reducing the agglomeration and improving the dispersibility of the MOS whiskers in the matrix, which results in the improved compatibility between the MOS whiskers and the polyvinyl matrix, as well as the processability of the composites.

For plasma polymerized (PP) thin films, many practical optical, electronic, sensing, and bio-applications are closely related to their surface properties. In particular, the surfaces of many PP films have a strong affinity for oxygen and moisture. Therefore, three different types of monomers which do not contain oxygen were selected to fabricate PP films, in order to understand the mechanisms for surface oxygen absorption. These monomers were a hydrocarbon, benzene (B); ferrocene (FC), containing Fe ions which have a great affinity for oxygen; and octafluorocyclobutane (OFCB), containing the strong electronegative (and thus oxygen repellent) element fluorine. X-Ray photoelectron spectroscopy (XPS), Fourier transform infra-red (FTIR) spectroscopy, and electron spin resonance (ESR) were used to explore the chemical composition and structure of the resulting PP films. XPS depth-profiling was also used to investigate the oxygen content in the bulk of the films by analyzing the film surface after various amounts of argon etching. The initial oxygen content on the surface of the PP-FC films was the largest of the three while PP-OFCB films only contained a trace quantity. PP-B films had an intermediate concentration. Affinity for oxygen for this latter film was determined to be due to residual activated species including free radicals and dangling bond sites on the film surface. Depth profiling disclosed little oxygen a short distance into the PP-B films, indicating that the oxygen was attracted after deposition upon exposure to ambient conditions. Although the PP-B film exhibited a high concentration of free radicals as determined by ESR, the dense and crosslinked bulk structure shielded these active centers in the film by prohibiting oxygen diffusion. For the PP-FC films, although a decrease in the amount of oxygen was observed after etching, a substantial concentration of oxygen exists with the depth, indicating incorporation of oxygen during the initial deposition. Because of the chemical nature of fluorine, the as-deposited PP-OFCB films did not exhibit significant affinity towards oxygen. However, a slightly oxygen enriched film surface was present after argon etching due to changes in the surface chemistry and structure. These results demonstrate that the formation and distribution of oxygen on and within the PP films are strongly dependent upon the chemical composition and structure of the films.

In a search for high current sources of low energy (\ensuremath{\approx}100 ev) negative atomic ions of hydrogen and oxygen, five types of sources were examined. The most promising practical source for both ${\mathrm{H}}^{\ensuremath{-}}$ and ${\mathrm{O}}^{\ensuremath{-}}$ was found to be the dc glow discharge from which beams of ${10}^{\ensuremath{-}7}$ ampere of either ion could be drawn. Hot cathode arc discharges yielded ${\mathrm{H}}^{\ensuremath{-}}$ currents of 7\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}8}$ ampere. Rf discharges, hollow cathode discharges, and sources involving the Arnot effect seem inferior as high current sources.Two results were found which are of interest both for the mechanism of the discharge and for the production of negative ions. First, the most copious source of negative ions seems to be the anode side of well-formed striations such as are present in the two superior sources. Second, when either of these sources is used, the beam noise in the low audiofrequency range is much greater than shot noise and is related to fluctuations in the striations.

Tuning the hydrophobicity of plasma polymer coated silica particles