Kinetics studies on copolymerization of acrylonitrile vinyl acids by solvent-water suspension polymerization

Polyacrylonitrile is an important polymer that is widely used in the manufacture of synthetic fibers, particularly for applications in apparel. Although a vast amount of literature is available on the polymerization process of acrylonitrile (AN) with other monomers, there are few reports of studies on polymerization in a mixed solvent of water with an organic solvent. It is conceivable that this method could combine the advantages of the solution and suspension polymerization methods. Synthesis of AN copolymers with two vinyl acids, methacrylic acid (MAA) and itaconic acid (IA), is carried out by solvent-water suspension polymerization. The polymerizations are performed with an equal ratio mixture of dimethylformamide as a solvent and water as a nonsolvent at 60 degrees C using alpha,alpha-azobisisobutyronitrile as an initiator. The kinetics of polymerization are studied by plotting the conversion versus reaction time for different mole ratios of AN with vinyl acids. Copolymers are characterized by FTIR and capillary viscometery. The results show that IA depresses the rate of polymerization more than MAA in this reaction medium, and this effect becomes more significant at higher vinyl acid mole ratios. High conversion in a short reaction time is obtainable for copolymers with a low vinyl acid mole fraction. However, for mole ratios of more than 93:7, the rate of the reaction is drastically reduced and low conversion (< 60%) results, even after 8 h. The intrinsic viscosities of all cases are surprisingly high. Although they are reduced with increasing acidic comonomer mole fraction, this reduction is more significant for IA compared to MAA. (c) 2005 Wiley Periodicals, Inc.