Copolymerization of acrylonitrile (AN) with acrylic acid (AA) carried out by solvent (DMF)-water suspension method, at 60 oC, using azobisisobutyronitrile (AIBN) as an initiator. The effects of mole fraction variation of acrylic acid and concentration variation of water in reaction medium, on the properties of synthesized copolymers were investigated by FTIR, viscometry, and DSC techniques. The reactivity ratios were calculated using Fineman-Ross and Kelen-Tudos methods. The results obtained show that by increasing the mole fraction of acrylic acid in the feed up to 0.0756, the conversion percentage decreases. However, the molecular weight increases in this range of feed ratio. In the samples prepared by keeping the feed ratio of comonomers constant and varying the ratio of the solvent/nonsolvent, the molecular weight increases by increasing nonsolvent amount. The reactivity ratio of AA is 6.5 times greater than that of AN. DSC Exothermic peak of homopolymer shows a single peak whereas, in copolymers it appears as doublets, due to more distinction of dehydrogenation, oxidation, and cyclization reactions.