Characterization Infrared (IR) and Surface electron microscopy (SEM) of asymmetric membranes based on Poly (acrylonitrile-co-vinyl acetate)

ABSTRACT

Asymmetric membranes, denominated respectively Mb1 and MB2, were obtained by the phase inversion method, employing the copolymer poly (acrylonitrile-co- vinyl acetate) - P (AN-co-VA) with an initial weight of composition 6.5% and 8.5% Polyvinylpyrrolidone (PVP). Membranes were characterized by means of spectroscopy techniques with Infrared Fourier Transform (FT-IR) and Scanning Electron Microscopy (SEM). Through the FT-IR technique it was possible to identify the bands that allowed showing the main functional groups present: i) in the base polymer ii) in the copolymer and iii) in the PVP polymeric additive used in the manufacture of membranes. Such bands are: in 2246 in cm^-1, band associated with the axial deformation of the C≡N group of acrylonitrile unit; in 1744 cm^-1, band associated with stretching of the carbonyl group (C = O), present in the comonomer ester or acid used in the polymerization of Polyacrylonitrile (PAN), and in 1242 cm^-1 (νC-O), band associated with the acetate groups present in copolymer P(AN-co-VA). The fundamental bands of PVP were identified in 1664 cm^-1 and in 1293 cm^-1 attributed to the stretching of the carbonyl group (C=O) attached to the amide and the stretching of the bond (-C-N), respectively. The results obtained by SEM pointed to structural changes in membrane morphology resulting from the increase in PVP concentration.

Keywords:
Asymmetric Membrane; Polyacrylonitrile; polyvinylpyrrolidone; FT-IR and SEM