Plasma Processes and Polymers

Cover: The synthesis and growth of silica-like nanoparticles from organosilicon precursors can take place within 0.1 s in continuous plasma reactors. The nucleated clusters grow by aggregation, agglomeration and accretion until the fluid element leaves the discharge and the growth is quenched. Further details can be found in the article by C. Roth, G. Oberbossel, E. Buitrago, R. Heuberger, P. Rudolf von Rohr on page 119.

The synthesis of silica-like nanoparticles from organosilicon precursors is studied in a continuous plasma reactor. The influence of plasma power, gas composition, residence time, and system pressure on the particle formation is investigated. A qualitative particle growth model consisting of four phases is introduced and applied to explain the changes in mass production, morphology, and chemistry.

The chemical and morphological features of the interface between plasma-treated PET substrates and silicon oxide coatings are investigated to clarify the influence of the interfacial features on the adhesive and cohesive properties of the polymer–oxide system. One-dimensional polymer protrusion and polymer–oxide composite nanostructures develop sequentially under the influence of strong plasma-ion irradiation and lead to low adhesion of oxide films with PET substrates.

Despite the importance of plasma polymers in biomaterial surface modification, the interplay between plasma polymer surface properties, protein adsorption and cell adhesion is poorly understood. It is shown that the wettability of the surface, the order in which the surface is exposed to the proteins as well as the time available for protein rearrangement are important factors that determine the final composition of the protein layer and thus result in different cellular.

B. subtilisspores in water were effectively inactivated in 6 min by a DC air plasma microjet. SEM images show clear distortion and debris of spores after plasma treatment. Short lived species (such as ^•OH, ^•O and O₂(¹Δ_g)) are detected in the plasma-water system by ESR spectroscopy, and are considered to be the most important agents in the inactivation process. Direct contribution from temperature, pH and long lived species are excluded.

Plasma technology was evaluated as a tool to modify polyamide 6.6 fibers and its relevance on the incorporation and release of an active principle. In vitro caffeine release showed that plasma gas flow increase improved significantly (up to 90% after 24 h) the delivery of active principle from the fabrics without altering the release mechanism from the fabrics.

It was possible to identify two types of free radicals, carbon centred and oxygen centred, that are generated as a result of PIII plasma treatment of PEEK. A significant increase in the free radical density was observed as a result of the PIII plasma treatment of PEEK films. The increase in free radicals led to a significant increase in the bonding strength of PEEK films.

Deposition of polymeric surfaces with controllable wettability is of a high interest from practical perspectives. Novel two-step method based on the combination of nano-clusters with plasma polymers is presented in this contribution. It is shown that this allows controlling independently two main parameters determining the wettability of surfaces—their roughness and chemical composition.

In this study quartz crystal microbalance is used as in situ diagnostic tool to measure protein deposit removal during plasma etching processes. The decontamination processes are described in terms of mass loss and etching kinetics of protein films is resolved. A self-limiting nature of the process is observed and explained in terms of chemical and morphological changes at the surface.

The biocompatible polymers are of a great importance in a tissue engineering and materials science. Both the plasma exposure process and thermal treatment was successfully applied for the polymer surface modification. The changes in physico-chemical surface properties caused by the treatment had a positive effect on polymers' biocompatibility, cell growth and adhesion.

The etching of the biphenyl by ArO₂afterglow occurs by interaction of the phenyl ring with the singlet state of molecular oxygen O₂(a¹Δ_g). [4 + 2] cycloaddition is assumed to be the main process leading to ring opening. Next, a large variety of compounds including alcohols, ketones, acids, and aldehydes are created. Atomic oxygen does not seem to play a significant role in the etching process.

The XPS C_1speak of the coating deposited in filamentary Ar/C₃F₆discharge can be fitted with five peaks. The chemical nature of the coating is characterized by nearly equal contribution of the CF, CF₂ and CF₃ bonds. The F/C ratio, also called Teflon character, is 1.09. The coating, with a thickness up to few microns, is deposited on micron-sized particles using PECVD in a fluidized bed.

A novel approach of fabricating white phosphorescent polymers is successfully developed. Direct injection of high concentrations of 1,10-phenanthroline into plasma reaction chamber allows excellent retention of desired monomer functionalities. Subsequent refluxing with the transition metal imparts broad-band fluorescence and phosphorescence. This simple approach offers great potential for white organic LED phosphorescent materials.