On the plasma polymerization

Effect of Discharge Frequency on the Plasma Polymerization of Ethane... 

The hydrodynamic factors that influence the plasma polymerization process pose a complicated problem and are of importance in the application of plasma for thin film coatings. When two reaction chambers with different shapes or sizes are used and when plasma polymerization of the same monomer is operated under the same operational conditions of RF power, monomer flow rate, pressure in the reaction chamber etc., the two plasma polymers formed in the two reaction chambers are never identical because of the differences in the hydrodynamic factors. In this sense, plasma polymerization is a reactor-dependent process. Yasuda and Hirotsu [22] systematically investigated the effects of hydrodynamic factors on the plasma polymerization process. They studied the effect of the monomer flow pattern on the polymer deposition rate in a tubular reactor. The polymer deposition rate is a function of the location in the chamber. The distribution of the polymer deposition rate is mainly determined by the distance from the plasma zone and the... 

In contrast to argon plasma, in which the sputtering of metal from the electrode is the primary process, the deposition of polymeric materials via plasma polymerization predominantly takes place in methane plasma. In such a polymer-forming plasma, the sputter deposition of electrode materials is considered as a secondary process, and the extent of the sputtering of metal depends on the plasma polymerization conditions, the nature of the electrode material, and the magnetic field strength. 

Most studies of plasma polymerization have been conducted in continuous wave rf plasmas. The effects of pulsed mode operation have received only limited attention. In a recent study, Yasuda et al. (1 ) found that while the polymerization rate of most monomers decreased when polymerization was carried out in a pulsed versus continuous plasma, the polymerization rate of a few monomers was enhanced. The present study was undertaken to determine the effects of pulsed operation on the plasma polymerization of ethylene and ethane. These monomers were selected because their behavior in continuous wave plasmas had been examined extensively in previous investigations (2 - ). ... 

Place grids with labeled bacteria on the cathode plate in a bell jar of the plasma polymerization replica apparatus. 

Gaseous monomer of ethane was purchased from the Matheson Gas Co.. The plasma polymerized ethane (PPE) was deposited on aluminum foil set on the discharge electrode throughout this work and the... 

A very common and useful approach to studying the plasma polymerization process is the careful characterization of the polymer films produced. A specific property of the films is then measured as a function of one or more of the plasma parameters and mechanistic explanations are then derived from such a study. Some of the properties of plasma-polymerized thin films which have been measured include electrical conductivity, tunneling phenomena and photoconductivity, capacitance, optical constants, structure (IR absorption and ESCA), surface tension, free radical density (ESR), surface topography and reverse osmosis characteristics. So far relatively few of these measurements were made with the objective of determining mechanisms of plasma polymerization. The motivation in most instances was a specific application of the thin films. Considerable emphasis on correlations between mass spectroscopy in polymerizing plasmas and ESCA on polymer films with plasma polymerization mechanisms will be given later in this chapter based on recent work done in this laboratory. 

Although to-date the emphasis has been on plasma polymerized films produced from hydrocarbon based systems, this trend in more recent times has swung towards fluorocarbons in an attempt to produce polymers of similar properties to conventionally prepared linear fluoropolymers. However, it will become clear from the account to follow that in many respects plasma polymerized fluorocarbons differ significantly from their linear counterparts. It is to the plasma polymerization of organic monomers containing solely carbon and fluorine therefore that we shall devote our attention in this section with only brief references to hydrocarbon and fluorohydrocarbon polymers for comparison purposes. 

How the starting molecules are fragmented into activated small fragments depends on the energy level of the plasma and the nature of the monomer molecules. This is a reason why plasma polymers possess different chemical composition when the plasma polymerization is operated at different conditions, such as different monomer flow rate, RF power, and pressure of the reaction chamber, even if the same starting materials are used for the plasma polymerization. 

Akovali and Ulkem [33] reported the surface modification of carbon black by plasma polymerization of styrene and butadiene. The effect of such plasma-coated carbon black was studied in a SBR matrix. A slight increase in the tensile strength was observed for the plasma-polymerized styrene-coated carbon black. This was explained by a decrease in the interfacial tension, as the result of the similarities between the treated filler and the matrix at the interface. They also concluded that the plasma coating obtained on carbon black is so thin that no blockage of the pores occurred and that there was no decrease in the original absorptive capacity. 

Amount of deposited material - The difference in weight loss between coated and untreated silica corresponds to the weight of the plasma-polymerized film deposited on the surface. For the plasma-treated silicas, decomposition of the coating starts at 265°C for poly acetylene, 200°C for polypyrrole, and 225°C for poly thiophene, and is complete at 600°C. Between 265 and 600°C, PA-silica shows 6 wt% weight loss, and PPy- and PTh-silicas show 4.5 wt% and 5 wt% loss, respectively. 

Alterations in the cytoskeleton. The cytoskeleton depends on the intracellular Ca2+ concentration, which affects actin bundles, the interactions between actin and myosin and a-tubulin polymerization. The effect of increases in Ca2+ on the cytoskeletal attachments to the plasma membrane and the role of the cytoskeleton in cellular integrity have already been mentioned (see above). If the cytoskeleton is damaged or disrupted or its function altered by an increase in Ca2+, then blebs or protrusions appear on the plasma membrane (see below). As well as an increase in Ca2+, oxidation of, or reaction with sulfydryl groups, such as alkylation or arylation, for example, may disrupt the cytoskeleton, as thiols... 

Fig. 39. Proposed structure of the plasma-polymerized toluene, based on the data from solid state 13C NMR of isotopically labeled toluene (from Ref. J31>)...

One should consider, however, that siloxane (like any polymeric matrix) will not create a hermetic interface. Even though it is hydrophobic in nature, it may still allow water penetration. The second possible explanation involves the change in the relative number of Si—O bonds that would need to be broken to create weakness in the system to the point of changing the peel locus of failure. It may be considered that the APS-siloxane network on the plasma-treated F-contaminated Si02 surface effectively brings another layer of Si—O bonds, the number of which may be too high to be effectively broken during the peel test [21]. 

Plasma polymer layers were deposited in the same reactor as described before. However, in this case, the pulsed plasma mode was applied. The duty cycle of pulsing was adjusted generally to 0.1 and the pulse frequency to 103Hz. The power input was varied between P 100 ()() V. Mass flow controllers for gases and vapours, a heated gas/vapour distribution in the chamber, and control of pressure and monomer flow by vaiying the speed of the turbomolecular pump were used. The gas flow was adjusted to 75-125 seem and the pressure was varied between 10 to 26 Pa depending on the respective polymerization or copolymerization process. The deposition rate was measured by a quartz microbalance. 

The XPS data reveal that a considerable degree of rearrangement of the injected fluorocarbon is involved in the plasma polymerization process. The relative quantities of CF, CF2, CF and non-fluorine substituted features are readily monitored by XPS and show a strong dependence on the injected fluorocarbon. As the fluorine content of the injected material decreases so does that of the polymer. Table 2 lists the measured F/C stoichio-... 

When the deposition rate and the system pressure shown on the recorder are confirmed to be steady, the deposition rate reading and the crystal temperature were recorded. Then changing the thermostat control of the circulating bath, while the plasma polymerization is kept at the steady state, lowered the temperature of the crystal. The deposition rate at the next temperature is read and recorded after steady-state readings are obtained at the new temperature. In this way, the relationship between deposition rate and substrate temperature can be obtained at a set of flow rates and power. A similar procedure is repeated for another set of flow rates and power. 

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