Polymerization of acrylonitrile in the presence of different solvents

The polymerization of acrylonitrile in ethylene carbonate and in dimethylformamide with azobisisobutyronitrile as initiator has been studied at 50°C. Polymerization occurs under homogeneous conditions in the range of monomer concentrations from 0 to 6 moles/l. in ethylene carbonate and from 0 to 4 moles/1. in dimethylformamide. Under these conditions the simple law usually valid for homogeneous polymerization is obeyed only when the monomer concentration is higher than 2.5 moles/l. At monomer concentrations lower than 2.5 moles/l. the reaction order with respect to monomer is increased. In the range in which polymerization is heterogeneous from the onset of the reaction, in ethylene carbonate the rates of polymerization as well as the molecular weights of the polymers, in dimethylformamide the rates only pass through a maximum with increasing monomer concentration. Owing to the chain transfer action of the solvent in polymerization the molecular weights of the polymers obtained in dimethylformamide increase continually as the monomer concentration is increased. The various features of heterogeneous polymerization are interpreted in terms of a concept recently proposed by us for the polymerization of vinyl chloride.