Ag(I) Catalyzed Grafting of Acrylonitrile onto Gum Arabic by Ce(IV) in Medium: A Kinetic Study

Grafting of Acrylonitrile (AN) onto water-soluble polymer Gum arabic (GA) was carried out using ceric ammonium sulfate [Ce(IV)] as initiator in the presence and absence of Ag(I) in H2SO4 medium at 313 K. The rate of oxidation (oxi), rate of grafting (g), and grafting efficiency (GE) were determined for catalyzed and uncatalyzed grafting and suitable mechanism was proposed to explain the observed results. No homopolymerization in the absence of GA indicates that the polymer obtained is purely a graft copolymer. A probable mechanism involving the formation of Ag(I)-GA adduct followed by its oxidation with Ce(IV) to give Ag(II)-GA adduct, and its decomposition to give initiating radicals is proposed to explain the observed results. The graft polymer was characterized using Fourier-transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), X-ray diffraction, and scanning electron microscopy (SEM) considering GA as reference.