Plasma polymerization comparison

Many applications of XPS to problems in adhesion science have been reported in the literature. One interesting example is provided by the work of Tsai et al. on the use of XPS to investigate reactions between model rubber compound and plasma polymerized acetylene films that was discussed above [22,23], Consideration of that system permits some interesting comparisons to be made regarding the type of information that can be obtained from RAIR and XPS. 

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. 

The results demonstrate the versatility of plasma polymerization of various monomers onto rubber fillers and vulcanization ingredients. The largest effects are seen in blends of different rubbers with unequal polarities. Substantial improvements in mechanical properties are seen in comparison with the use of unmodified fillers and curatives. 

In parylene polymerization, the thermal cracking of the dimer (starting material) creates monomeric diradicals. All starting materials are converted to the reactive species, i.e., diradicals. No specific initiator for the chemical structure of starting material is formed. The situation is close to that of plasma polymerization. The comparison of plasma polymerization and radiation polymerization, and the comparison of the two vacuum deposition polymerizations (parylene polymerization and plasma polymerization) enable us to construct an overall view of material formation in the luminous gas phase. 

Figure 6.9 Comparison between the TMS and the CH4 signals obtained by the DC cathodic plasma polymerization method (5 W, 50 mtorr, 3 min) (a) TMS plasma (b) CH4 plasma.

Because of the unique growth mechanism of material formation, the monomer for plasma polymerization (luminous chemical vapor deposition, LCVD) does not require specific chemical structure. The monomer for the free radical chain growth polymerization, e.g., vinyl polymerization, requires an olefinic double bond or a triple bond. For instance, styrene is a monomer but ethylbenzene is not. In LCVD, both styrene and ethylbenzene polymerize, and their deposition rates are by and large the same. Table 7.1 shows the comparison of deposition rate of vinyl compounds and corresponding saturated vinyl compounds. 

According to this scheme of plasma polymerization of TMS in a closed system, it is anticipated that the atomic composition of the plasma polymer should continuously change with the plasma polymerization time. Figure 13.21 depicts comparison of XPS cross-section profile of C/Si ratios for plasma polymers deposited in a flow system reactor and that in a closed system reactor. The results clearly show that a closed system plasma polymerization of TMS indeed produces a... 

Table 9-8. Dielectric Properties of Plasma-Polymerized Films in Comparison with Conventional Polymers at Temperature 20°C and Frequency 1 kHz...

Aramid tire cords have been treated by argon plasma etching and plasma polymerization of acetylene. The combination of argon plasma etching and acetylene plasma polymerization results in a greatly improved pull-out force of 91 N in comparison to 34 N with the untreated aramid tire cord. Thus, the plasma treatment improves the adhesion to rubber compounds. " ... 

Polybutadiene/polycarbonate membranes with a pp-ethylenediamine layer had an increased gas permeability (in comparison with the unmodified one) due to surface etching. Their selectivity was closely connected with the chemical composition of the top layer. A high nitrogen content was required for high O2 selectivity (Ruaan et al. 1998). The presence of the amine groups on the membrane surface also enhanced the capacity for CO2/CH4 separation. The plasma-polymerized diisopropylamine on the surface of the composite membrane—porous polyimide (support)/ silicone (skin)— made the separation coefficient as high as 17 for a permeation rate of 4.5 X cmVcm sec cmHg (Matsuyama et al. 1994). 

Fig. 5.3 Comparison of experimental data obtained for plasma-polymerized vinylferrocene (solid circles) and the theoretical calculation (open circles) according to (5.39). (Reproduced from [14] with the permission of Elsevier)...

The non-equilibrated, low-temperature plasma which is generated by glow discharge in gases is very suitable for the modification of polymer surfaces. Examples are plasma polymerization and plasma treatment In comparison with these plasma applications, plasma-induced graft copolymerization has attracted the attention of only very few researchers. 

Clark DT, Abu-Shbak MM (1984) Plasma polymerization. XL A comparison of the plasma polymerization of the isomeric perfluorinated diazines. J Polym Sd Polym Chem Ed 22 17-28... 

The plasma polymerization ofphosphazene monomers was the subject of a 1982 U.S. Patent [40], wherein the phosphazene monomers studied were trimers and tetramers substituted with halides or organic nucleophiles. Experiments were conducted by direct exposure of crystalline trimer to the plasma, followed by extraction of the residues into warm tetrachloroethane. It was concluded that the resultant polymers were crosslinked and formed in low yield (-10%). Another experiment used an initial plasma polymerization followed by post-plasma treatment at 210 °C. On comparison with a control sample which was subjected only to the post-plasma treatment, some polymerization was observed, although the only residues formed were insoluble in toluene. 

Figure 8 illustrates a comparison between measured and computed rates of butadiene polymerization in an rf plasma sustained at 13.56 MHz. A perfect fit is achieved by adjusting the rate coefficients appearing in the model to the following values ... 

Figure 13.8. The second is that the edge effect was depressed in comparison with that at 50mtorr as observed in Figure 13.8. As a result, an even more uniform plasma deposition was achieved with DC cathodic polymerization that was carried out at higher system pressure (at a fixed flow rate).

The significance of LCVD is in the unique aspect of creating a new surface state that is bonded to the substrate material particularly polymeric material. The new surface state can be tailored to be surface dynamically stable. However, caution should be made that not all LCVD films fit in this category. Appropriately executed LCVD to lay down a type A plasma polymer layer creates surface dynamically stable surface state. In the domain, in which surface dynamic instability is a serious concern in the use of materials, a nanofilm by LCVD is quite effective in providing a surface dynamic stability, and other methods do not fare well in comparison to LCVD. 

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