Azine bridge formation during the electrografting of acrylonitrile

Abstract

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 À1 and a second band at 1096 cm À1 , 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.

Moisturized Polyacrylonitrile Copolymer for Stronger Precursor Fibers

“…According to FT-IR data, moisturization did not induce structural changes in the copolymer in the EPAN fibers (Figure S8). The amide peak at 1664 cm –1 was less intense in the EPAN0.5, EPAN1.0, and EPAN1.44 samples compared with the EPAN0 sample, which indicates less residual DMF . This was attributed to the prevention of DMF adsorption by the more readily adsorbed water molecules.…”

“…Moisturization of PAN did not result in molecular structural changes according to FT-IR data (Figure S6). The peak at 1664 cm –1 , attributed to the amide peak of residual DMF, was evident in the FT-IR spectra of the GPAN fibers, and the peaks of the AN-derived CH 2 anti-symmetrical and symmetrical vibrations (2920 and 2840 cm –1 , respectively), CN (2242 cm –1 ), and CH 2 deformation (1440 cm –1 ) and of the MA derived CO stretching (1730 cm –1 ), O–CH 3 deformation (1380 cm –1 ), and C–O stretching (1255 and 1090 cm –1 ) were observed. , …”

“…The sample codes are denoted as EPAN0, EPAN0.5, EPAN1.0, and EPAN1. 44, where the numbers indicate the adsorbed water content. Similar to the GPAN fibers, the EPAN fibers displayed uniform morphology.…”

“…The amide peak at 1664 cm −1 was less intense in the EPAN0.5, EPAN1.0, and EPAN1.44 samples compared with the EPAN0 sample, which indicates less residual DMF. 44 This was attributed to the prevention of DMF adsorption by the more readily adsorbed water molecules. The reduced DMF adsorption was not expected to affect the strength of the EPAN fibers.…”

Covalent Bonding of Functional Coatings on Conductive Materials: the Electrochemical Approach

“…As far as PAN is concerned, Fourier transform infrared (FTIR) analysis [58] also confirmed the absence of cross-linking, which had, however, been suggested earlier [59][60][61]. However, these chains are completely desorbed when the surface is immersed in an electrolytic solution (without monomer) and cathodically polarized in the range of the second voltammetric peak.…”