Organic Syntheses in the Plasma of Glow Discharges and Their Preparative Application

Abstract

It is only during the last few years that reactions of organic substances as a result of electron collisions in the cold plasma of glow and corona discharges have been developed into a preparatively useful method with a wide range of possibilities. Its basic principles and development prospects are discussed in the present progress report on the basis of the research results that are known at present.

Carbon Nanotube-Polypyrrole Composite Electrode Materials Produced In Situ by Electron Bombardment in Radio-Frequency Plasma Afterglows

“…Formation of larger multi‐ringed PAHs during plasma polymerization is characteristic of inert systems, and three ring PAHs have been found to be most prevalent in experiments on soot formation using benzene in inert plasmas . Experiments have shown that plasma reactions between linear unsaturated hydrocarbons in the presence of nitrogen can produce both pyrrole and pyrrole‐like compounds, as well as carbazole and larger ring structures as well . The presence of PPy‐PP in spectra confirms that it is present in the gas phase around the sample, and that deposition occurs from the plasma onto the surface, but it does not give any information on the molecular weight of the plasma polymer or whether it is stable in the RF afterglow.…”

“…Nonetheless, the findings clearly showed a plasma synthesis mechanism that produced higher molecular weight cyclical molecules during plasma treatments. The synthesis of pyrrole and other amide molecules by plasma cyclization of unsaturated hydrocarbons has been known for some time . Addition of oxygen inhibited this mechanism in experiments that were undertaken in excess oxygen .…”

Mechanisms of Plasma Polymerization – Reviewed from a Chemical Point of View

“…are generally absent in plasma polymers 14, 36, 102. However, formation of linear molecules and oligomers, such as biphenyl, diphenylether, or diacetylene, has frequently been reported 24, 25, 103. They may act as initiator (mesogene) of orientation of neighboured (macro‐) molecules (rod‐like units, which enforce the orientation in their surroundings) 103.…”

“…Compositions and structures of plasma polymers were investigated by bulk‐ and surface‐analytical methods. Bulk methods used were IR transmission spectroscopy,7, 41 dielectric relaxation spectroscopy (DRS),40, 99, 100, 130, 131 electron spin resonance (ESR),13–136 thermo‐luminescence (TL),137, 138 thermo‐gravimetry (TG),13, 139, 140 1 H‐ and broadline NMR 42, 135. All results of bulk analyses reflect the total absence of structural and compositional regularity in plasma polymers, regardless of whether they are produced by cw‐ or pulsed plasma.…”

“…Such irregular structures are also produced through constant bombardment of the growing layer by energetic plasma particles and UV photons 21, 22. Neiswender,9 Dinan,23 Suhr/Rosskamp,24, 25 and Friedrich et al26 also largely attributed plasma polymerization to a random poly‐recombination of radicals, but additionally and speculatively to the sticking of C 2 species, thus forming multiples (C 4 , C 6 , C 8 ) such as acetylene, cyclobutadiene, diacetylene, phenylacetylene, 2 + 2 adduct of cyclobutadiene, octatetraene and styrene, as well as plasma polymers (Figure 1).…”