Polymerization Kinetics of Poly(amidoamine)s in Different Solvents

The polyaddition kinetics of 2-methylpiperazine to 1,4-bisacryloylpiperazine was determined in water, methanol, ethylene glycol, formamide, and dimethylformamide, respectively. In the protic solvents the polyaddition proceeded through a two-step mechanism, each step involved one of the two different secondary amino groups; the difference in amine reactivity was ascribed to the different steric hindrance by the neighbouring groups. Each step followed pseudo-second-order kinetics; the kinetic constants included the catalytic protonic species. In the case of dimethylformamide, the polyaddition proceeded through third-order kinetics; this accounted for the autocatalytic activity of the amino groups. The apparent kinetic constants in the protic solvents increased with the increase in the autoprotolysis constant values and decreased with the increase of the dipole moment.