The IR spectra of PAN, its copolymer and terpolymer are shown in Figure 3. In all cases, the bands in the region of 2943 cm−1 were assigned to C–H stretching in CH, CH2 and CH3. The bands at 1450 cm−1, 1353 cm−1 and 1204–1199 cm−1 were due to the C-H vibrations of different modes. The band at 2244 cm−1 indicated the absorption of nitrile groups in PAN homopolymer, copolymers and terpolymers [26]. The band in the region of 1632 cm−1 was assigned to the stretching of NH2 groups due to acrylamide formation by partial hydrolysis of acrylonitrile units during the polymerization process using redox initiator [27]. The strong band in the range of 1735 cm−1 in copolymer and terpolymer spectra was due to the C=O stretching [26,29]. The disappearance of bands at 2238–2239 cm−1 that are due to the stretching of unsaturated nitriles of FN [30] confirms that FN was incorporated into terpolymers. It was reported that fumaronitrile cannot homopolymerize but copolymerizes easily under free radical condition