Copolymerization of acrylonitrile (AN) with acrylic acid (AA) was carried out in deionized water (DI) at 40 °C by free radical polymerization method using sodium bisulfite (SBS) and potassium persulfate (KPS) as redox initiators. The synthesis of poly(AN/AA) was investigated with mole ratio of AN/AA; 100/0, 97/3, 95/5, 93/7 and 90/10. The poly(AN/AA) was then modified with hydrazine hydrate via nucleophilic addition reaction. The functional groups, morphology and polymer contents (carbon, hydrogen, nitrogen and sulphur) of the poly(AN/AA) and hydrazined poly(AN/AA) were characterized by Fourier Transform Infrared (FTIR) spectroscopy, Scanning Electron Microscopy (SEM) and Elemental analysis respectively. The yield of polyacrylonitrile (PAN) was 73% and decreased as the amount of AA increased. The successful of polymerization was confirmed by the appearance of C≡N functional group at 2240 cm-1 and the incorporation of acrylic acid in copolymer system was established by the appearance of C=O at 1730 cm-1 from the IR spectra. The polymer modification was successfully accomplished by the complete disappearance of C≡N from IR analysis. The SEM images have shown that the average spherical diameter of poly(AN/AA) and hydrazined poly(AN/AA) were ~130 nm and ~150 nm respectively.