While I was at CSIRO in 1997-1998 I had the opportunity to work on plasma polymerization and really dig into some of the variables that can affect the surface modification of polymers with “monomers”.  Monomers in this sense are not unsaturated compounds but rather small molecules with reactive functional groups and aliphatic groups (methyl, ethyl, etc).  Glow discharge plasma methods are generally very messy, ripping molecules apart and recombining them.  When performing surface modification of polymeric materials, the exposed aliphatic groups of the polymer surface are also ripped apart, and in the presence of one of these “monomers” can then react with the monomer fragments to create functional groups on the surface.  The group at CSIRO Chemicals & Polymers published a number of papers in this area, some of which are in the references of the paper. We were able to surface modify films with amines, siloxanes, and various aldehydes just to name a few to render different surface properties. 

In the example given here of previously unpublished work, the incorporation of a quartz crystal microbalance (QCM) into a glow discharge plasma reactor allows the direct measurement of deposition rates from plasma polymerization.  To accomplish this task, we first measured the deposition rate of acetaldehyde plasma polymers under various conditions of monomer flow rate and RF power input using a QCM apparatus and correlated it with XPS data. From a large number of experiments a family of curves resulted for deposition rate vs. a specific Yasuda composite parameter W/F (power/flow rate).  These curves have an excellent fit for deposition rate vs. the natural log of W/F of the form A*ln(W/F) + b.  Plotting the empirical values of the pre-logarithmic term A and intercept b, a general equation predicting the rate of deposition of acetaldehyde plasma polymers for a given power and flow rate was obtained.  This reduces the characterization of a system to a few variables that can then be artfully controlled to provide consistent results. 

I hope you find the article interesting, and please feel free to contact me if you have any questions or comments.  Thanks for visiting my page!

Plasma Polymerization Rates

Dr. Henry Oviatt

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