Formation of Plasma Polymer Thin Films Containing Reactive Metal Chelate Sites

We report here the successful incorporation of chemically active Co2+ and Ni2+ centers into plasma polymer thin films. Metal center incorporation was accomplished by simultaneous plasma polymerization of sublimed Co2+ or Ni2+ complexes with gaseous “comonomers” or Ar. The metal complexes include N,N′-bis(salicylidene)-1,2-phenylenediaminecobalt(II) (CoSalophen), N,N′-bis(salicylidene)ethylenediaminecobalt(II) (CoSalen), N,N′-bis(3-fluorosalicylidene)ethylenediaminecobalt(II) (CoFluomine), meso-tetraphenylporphyrinatocobalt(II) (CoTPP), meso-tetraphenylporphine (TPP), and meso-tetraphenylporphyrinatonickel(II) (NiTPP). Modification to the metal complex structure was observed by IR and UV-vis spectroscopies. IR spectra of plasma polymer films containing the Schiff's base complexes, prepared using Ar as a carrier gas, contained a band at 2190 cm−1, which can be attributed to nitrile group formation, and would necessarily result from destruction of the Co2+ inner coordination sphere. This type of bond cleavage was eliminated by the use of polymerizable “comonomers” instead of Ar. IR spectra of CoFluomine films exposed to pyridine vapor indicate that pyridine is chemically bound within the films. Gravimetric analysis of the CoFluomine films revealed that the pyridine is bound in a 1:1 Co:pyridine ratio, suggested that the metal center remains chemically active. IR spectra of plasma polymer films containing the porphyrin complexes contain evidence for modification to the phenyl and pyrrole rings, indicating that the complexes may be attached to the plasma polymer matrix at these sites. UV-vis spectra of plasma polymer films containing CoTPP contain a band at 610 nm which may be due to chlorin formation, which is consistent with pyrrole ring substitution. Plasma polymer film solubility in toluene was used to estimate the extent of crosslinking within the films. Solubility was found to generally increase with increased concentration of complex in the films. This is discussed in terms of increased deposition rate and decreased glow discharge pressure during synthesis of films with higher metal chelate content. © 1994, American Chemical Society. All rights reserved.

Duke Scholars

Author Alvin L. Crumbliss Chemistry