FT-IR-ATR Spectroscopic Study of Alkali-treated Polyacrylonitrile Films

Abstract

Chemical reaction at the surface of polyacrylonitrile (PAN) films by alkali treatment has been investigated by FT-IR-ATR spectroscopic method. The chemical species produced at the film surface were analyzed from the difference spectrum between the spectra before and after the reaction. The difference spectrum showed that the surface of the PAN film is partially hydrolyzed to produce polyacrylamide (PAAm) and poly(sodium acrylate) (PSA). A method was proposed to determine the chemical species at the surface of the film quantitatively. The quantitative determination was made by the use of the ratio of absorbances of the characteristic bands of each component at the treated film to those of each of component homopolymers in the ATR spectra. In the method errors caused by incomplete contact between the internal reflection element and the sample were corrected. It was found that PAAm was a chief product at the early stage of the reaction while the content of PSA increased with the progress of the reaction. When H₂O₂ was added into the reaction solution, PA Am was found to be a chief product at the film surface irrespective of the reactio n time. The reaction was limited to a very thin surface layer for PAN homopolymer. The alkali treatment was also investigated for copolymers of acrylonitrile and hydrophilic monomers such as N-vinyl-2-pyrrolidone or sodium 2-methyl-2-propene-l-sulfonate). In this case, the reaction occurred to a very large depth as compared with the homopolymer film.