Kinetics of polymerization of nitroethylene. III. High molecular weight polynitroethylenes

The polymerization of nitroethylene in dimethylformamide and tetrahydrofuran was studied in a wide temperature range. Pyridine and 3‐methyl‐4‐ethyl‐pyridine were used as catalysts. Polymerization was followed by adiabatic temperature rise as well as gravimetrically. At low temperatures the kinetics are first order with respect to catalyst and monomer. The degree of polymerization (at −75°C. in dimethylformamide and at −104°C. in tetrahydrofuran) is proportional to the degree of conversion. High molecular weight polymers are formed with intrinsic viscosities of the order of 2. In the intermediate temperature range (about −30°C.) the rate of reaction in dimethylformamide may be expressed by: At room temperature (0–25°C.), the kinetics are second order with respect to monomer in both solvents. The apparent activation energy is negative and low molecular weight polymers are obtained. The following mechanism is suggested in order to explain the experimental findings: The interaction of catalyst and monomer produces an active dipolar adduct, and the chain is propagated by a polar mechanism. The termination of the growing chain may take place spontaneously or by transfer of the catalyst to monomer. The activation energies associated with termination reactions are much higher than Ei and Ep, therefore at low temperatures the rates of both termination and transfer are approaching zero, while those of initiation and propagation are much less affected. At a sufficiently low temperature, which depends upon the dielectric constant of the solvent, the formation of “living” polymer is postulated.