Propagation rate coefficients for styrene solution polymerization in dimethyl formamide and acetonitrile

The technique of pulsed-laser polymerization was used to measure the propagation rate coefficient (kp) of styrene in dimethyl formamide and acetonitrile over a range of monomer concentrations at 40°C. A significant solvent effect was observed in both solvents. In dimethyl formamide, the kp value systematically falls, as the monomer concentration decreases, to a value that is (at 1 mol l−1 of styrene) approximately 75% of the bulk kp. In acetonitrile, the kp is also reduced. In this case, however, the kp value has a minimum at an intermediate dilution.