Plasma deposition polymerization, surface

Plasma treatment and plasma deposition polymerization provides a unique and powerful method for the surface chemical modification of polymeric materials without altering their bulk properties. (7-5) These techniques offer the possibility to improve the performance of existing biomaterials and medical devices and for developing new biomaterials-(- -6)... 

Abstract Plasma polymerization is a technique for modifying the surface characteristics of fillers and curatives for rubber from essentially polar to nonpolar. Acetylene, thiophene, and pyrrole are employed to modify silica and carbon black reinforcing fillers. Silica is easy to modify because its surface contains siloxane and silanol species. On carbon black, only a limited amount of plasma deposition takes place, due to its nonreactive nature. Oxidized gas blacks, with larger oxygen functionality, and particularly carbon black left over from fullerene production, show substantial plasma deposition. Also, carbon/silica dual-phase fillers react well because the silica content is reactive. Elemental sulfur, the well-known vulcanization agent for rubbers, can also be modified reasonably well. 

Plasma deposition on a hydrogen-containing surface from HFE is a selfterminating plasma polymerization process. When the initial plasma polymer surface, which contains hydrogen atoms, is sufficiently covered by the plasma polymer of HFE, the deposition ceases because the supply of hydrogen diminishes. 

It is important to note that plasma deposition occurs predominantly on the cathode surface in the cathodic polymerization, and a new cathode (substrate) was used in every plasma coating operation. In other words, the contamination of the reactor is considered to be minimal. 

Furthermore, in this type of plasma the polymeric materials deposit not only on the substrate but also on the electrode surfaces. Thus, the sputter deposition of metal in polymer-forming plasmas is more complicated than that in non-polymer-forming plasmas. 

The influence of the surface area of cathode on the plasma deposition rate is shown in Figure 15.27. It is clear that the plasma deposition rate decreases with the increase of cathode surface area. This is because plasma deposition rate is proportional to current density in cathodic polymerization as described in Chapter 8. The patterns of distribution due to magnetron configuration are similar, but the trends are magnified as the deposition rate increases with smaller cathode area. 

The (TMS 02) plasma-modified polymers were made considerably more hydrophilic with average cos 0D,a,i= 0.654 (Op,a,i =49.2 11.7) but remain in the domain of amphoteric surface, under the conditions of plasma polymerization used. (TMS + O2) plasma-deposited films were slightly more dependent on the nature of the conventional polymer substrates. This is probably due to the fact that substrate polymers have different oxygen plasma susceptibilities. 

Plasma deposition has also been utilized to deposit PEO-like materials from volatile precursors onto a variety of subjects. This technique involves generating a reactive plasma containing PEO-like monomers, which polymerize and deposit, often with chemical grafting, onto any surface within the plasma. The availability of large-scale vacuum apparatus makes this technique feasible on an industrial scale. The materials deposited by this technique were often shown to contain only short PEO segments yet greatly reduced protein deposition was observed and the small amounts (ng/cm) that did deposit were easily eluted. ... 

In the grafting from approach, a surface, that was previously activated e.g. by plasma treatment, is exposed to a monomer solution (Huang et al. 2003). A more simple, one-step procedure is to inadiate a polymeric surface like TCP, which is covered with the monomer solution, by an electron beam (Yamada et al. 1990). Alternatively, ultraviolet light and a photosensitiser can be utilised to initiate polymerisation and cross-linking (Curti et al. 2005). A completely different route to prepare thin SRP coatings with good adhesion to solid substrates is plasma polymerisation (Biederman and Osada 1992). In this case, NIPAAm is used as a precursor in a plasmachemical thin film deposition process (Cheng et al. 2005 Pan et al. 2001). 

Yameen B, Khan HU, Knoll W, Foerch R, Jonas U. Surface initiated polymerization on pulsed plasma deposited polyallylamine a polymer substrate-independent strategy to soft surfaces with polymer brushes. Macromol Rapid Commun 2011 32(21) 1735—40. 

More recently, an approach for low permeability materials is to deposit parylene-C into the poly-(dimethylsiloxane). The base matrix is coated with parylene-C by chemical vapor deposition polymerization in the usual way [78]. Then the parylene-C on the surface is removed by oxygen plasma etching and only what is in the pores of the matrix remains there. 

Another approach was developed using two-step deposition polymerization to make the direct formation of patterned PPy thin film [260]. The surface roughness of PPy films was much lower than that of conventional PPy film. The film surface was formed with an apparent granular structure of the dimension less than 300 nm. The conductivity of iodine-doped PPy was also comparable to that of PPy film formed by plasma polymerization or electrochemical deposition. 

Plasma-deposited allylanune films were studied by in situ ToF-SIMS before exposure to ambient air by Oran et al. [151]. The results indicated that aUylamine monomer s primary amino groups were partially transformed into other nitrogen functionalities during plasma polymerization. The same principle was applied for acrylic acid (AA) monomers. The resulting polymer films were used for surface modification of T1O2 nanoparticles [152], By means of SIMS, it was shown that AA films contain low MW oligomeric components. 

---