Plasma derived polymers, properties

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. 

The chemical and physical properties of plasma polymers derived from a monomer are dependent on many factors of overall conditions of plasma polymerization. In other words, a monomer does not yield a well-defined polymer in plasma polymerization. The variation of properties is largely influenced by the energy input parameter of plasma polymerization, WjFM, as described in Chapter 8. 

It is well known that the surface chemical and physical properties play a dominant role in the separation characteristics of a membrane. Most of the currently used membranes are made of polymers because they have excellent bulk physical and chemical properties, they are inexpensive, and are easy to process. However, the surface properties of polymers, their hydrophobicity, and their lack of functional groups stand in the way of many other applications (Chan et al. 1996). So far, various polymers have been used for membrane fabrication. However, due to the limited number of polymeric materials on the market, one cannot expect any significant increase in the variety of the membranes offered. What is more, large-scale production of brand-new polymers has not been commercialized during the last decade, nor is it expected to be launched in the near future. These observations have forced material scientists to search for alternative methods to increase the number and variety of membranes being prepared. There are two directions for new membrane manufacturing (i) to modify a polymer in bulk and then prepare the membrane from it or (ii) to prepare the membrane from a standard polymer and then modify its surface. The first method needs the optimization of the membrane formation for the particular derivative separately. The second seems to be less complicated and less expensive, and it can offer a wide variety of new membranes based on one starting matrix. The authors intention is to present the plasma methods for membrane modification and tailor them based on the end-user requests. 

---