Plasma-polymerized film

Fig. 39. Auger depth protile obtained from a plasma-polymerized film on a polished steel substrate after the film was reacted with a model rubber compound for 65 min. Reproduced by permission of Gordon and Breach Science Publishers from Ref [45].

Z.Y. Wu, Y.H. Yan, G.L. Shen, and R.Q. Yu, A novel approach of antibody immobilization based on n-butyl amine plasma-polymerized films for immunosensors. Anal. Chim. Acta 412, 29-35 (2000). 

K. Nakanishi, H. Muguruma, K. Ikebukuro, and I. Karube, A novel method of immobilizing antibodies on a quartz crystal microbalance using plasma-polymerized films for immunosensors. Anal. Chem. 68, 1695-1700 (1996). 

Tanaka A, Sekiguchi Y, Kuroda S. A new replica method for electron microscopic studies of a plasma polymerization film with a glow discharge. Seikagaku 1983 55 1212-1219. (in Japanese)... 

JD Affinito, ME Gross, PA Moumier, MK Shi, and GL Graff, Ultrahigh rate, wide area, plasma polymerized films from high molecular weight/low vapour pressure liquid or solid monomer precursors, J. Vac. Sci. Technol., A, 17 1974—1981, 1999. 

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. 

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. 

The most extensive studies of plasma-polymerized membranes were performed in the 1970s and early 1980s by Yasuda, who tried to develop high-performance reverse osmosis membranes by depositing plasma films onto microporous poly-sulfone films [60,61]. More recently other workers have studied the gas permeability of plasma-polymerized films. For example, Stancell and Spencer [62] were able to obtain a gas separation plasma membrane with a hydrogen/methane selectivity of almost 300, and Kawakami et al. [63] have reported plasma membranes... 

Marchant RE, Johnson SD, Schneider BH, Agger MP, Anderson JM. A hydrophilic plasma polymerized film composite with potential application as an interface for biomaterials. Journal of Biomedical Materials Research 1990, 24, 1521-1537. 

Preparation and Characterization of Active Glucose Oxidase Immobilized to a Plasma-Polymerized Film... 

This study on the immobilization of glucose oxidase and the characterization of its activity has demonstrated that a bioactive interface material may be prepared from derivatized plasma polymerized films. UV/Visible spectrophotometric analysis indicated that washed GOx-PPNVP/PEUU (2.4 cm2) had activity approximately equivalent to that of 13.4 nM GOx in 50 mM sodium acetate with a specific activity of 32.0 U/mg at pH 5.1 and room temperature. A sandwich-type thin-layer electrochemical cell was also used to qualitatively demonstrate the activity of 13.4 nM glucose oxidase under the same conditions. A quantitatively low specific activity value of 4.34 U/mg was obtained for the same enzyme solution by monitoring the hydrogen peroxide oxidation current using cyclic voltammetry. Incorporation of GOx-PPNVP/PEUU into the thin-layer allowed for the detection of immobilized enzyme activity in 0.2 M sodium phosphate (pH 5.2) at room temperature. 

The organic thin films used in lithography are polymer casting films, Langmuir-Blodgett (LB) films, SAMs and plasma-polymerized films. The molecular designs and syntheses of organic monolayer materials are studied for SPNL resists [89]. 

Because powder formation can be characterized as the rapid formation of polymeric species in a localized gas phase, the quantity of particles or powders mixed in a coherent film that forms at a substrate surface should also be related to the rate of film formation. Thompson and Smolinsky [8] found a direct correlation between the particle density on the surface of a plasma-polymerized film and the growth rate of the film as depicted in Figure 8.14. 

Figure 8.19 Infrared spectra of (a) low-density polyethylene film, (b) plasma-polymerized film, (c) plasma-polymerized powder. Adapted from Ref. 11.

The morphology of the plasma polymerized films has been examined by electron microscopy by a number of workers ( 3,, 48). Figure 12 shows the replica electron micrograph of plasma polymerized ethylene deposited on chromium substrate at several gas pressures (46). The presence of powder particles is clearly evidenced in Figures 12a-c. The size and density of the powdery products decrease with increasing pressure until at a pressure of 3 torr when the polymer is mainly film and contains very few particles. 

Figures 13 and 14 compare the surface structures of the plasma polymerized ethylene on Teflon, and cleaved mica ( 6). Because of the rougher initial surface on Teflon, there is a greater concentration of powder on that surface. The mica surface is smooth before polymer deposition. The polymer films are also very smooth and featureless, indicating the strong dependence of morphology of plasma polymerized films on the surface roughness of the substrates.

Plasma polymerized films are thin (from hundreds of angstroms to several microns) and pinhole-free. 

Figure 15. IR spectra of plasma-polymerized films on sodium chloride substrate...

Electron spectroscopy (ESCA) has been found to be particularly useful for the structural analysis of plasma polymerized film surfaces. Most of the applications are directed to fluorocarbon polymers because of the large chemical shifts in the binding energies of C(ls) electrons caused by fluorines bonded to carbon. 

There has been a great deal of interest in the study of the electrical properties of plasma polymerized films. Early data on the dielectric and conductivity of the films has been reviewed by Mearns ( ). More recently, the dielectric properties of plasma polymerized styrene (69-71), acrylonitrile (72), hexamethyldisiloxane (73-75), tetrafluoroethylene... 

The conductivity and capacitance of plasma polymerized films has also been reported by numerous workers (72,77-81). Morita, et. al. (81) found that the dc conduction current decreases when exposed to oxygen, and attributed the decrease to the disappearance of space charge on exposure to oxygen. Harai and Nakada (72) suggested that the dc conductivity effects of plasma polymerized acrylonitile can be adequately interpreted by the field assisted ionization of impurity levels first enunciated by Poole and Frenkel (82). ... 

Stancell et. al. ( 0) reported the possible use of ultrathin films deposited onto relatively permeable substrates as permselective membranes. Ultrathin and highly crosslinked coatings effectively distinguish between molecules of different sizes and increase the permselectivity of the substrate film. Chang et. al. ( ) demonstrated that the permeability coefficient of silicone rubber to oxygen decreased noticeably after depositing a plasma-polymerized ethylene film on the surface. Colter, et. al. (92.93) found similar effects of plasma polymerized films as diffusion barriers in controlled-released drug delivery systems. 

Effects of Plasma-Polymerized Film on the Current-Voltage Characteristics of Single Probe... 

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