Azine bridge formation during the electrografting of acrylonitrile
2009
Easter, Penelope A. | Taylor, D Martin
We report the electrografting of polyacrylonitrile (PAN) films onto evaporated gold, silver, and copper substrates, and onto platinum foil. The FTIR spectra of the films are virtually identical to library spectra of PAN and show no evidence of the cyclization observed by some authors. Raman spectra of the same films, however, display a broad absorption band centered at ~1520 cm⁻¹ and a second band at 1096 cm⁻¹, which are neither present in spin-coated films of commercially obtained PAN nor are they present in the FTIR spectra. These previously unreported Raman bands are dependent on a number of factors in the electrografting process; the working electrode metal, the monomer concentration, the solvent used, and the electrochemical protocol used for cleaning the working electrode. The relative intensity of the bands was found to be strongest in films grown on platinum and weakest in those grown on gold, and stronger in thin films (<50 nm) than in thick films (>100 nm). We suggest that these new spectral features are associated with azine-linked polymer chains in a ladder-like structure close to the electrode surface as a result of the predominantly isotactic brush-like conformation of the polymer during the early stages of electrografting.
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