FREE-RADICAL COPOLYMERIZATION .5. RATE CONSTANTS OF PROPAGATION AND TERMINATION FOR A STYRENE METHYL-METHACRYLATE TOLUENE SYSTEM

The free-radical copolymerization of styrene and methyl methacrylate at 40 degree C in the presence of 50 wt% of toluene was critically examined by studying both the steady-state and nonsteady-state polymerizations and thus evaluating the rate constant of propagation and termination individually as a function of monomer composition. The results closely agree with those for the corresponding bulk system, establishing that the propagation step of this system, which the terminal model fails to describe, obeys the penultimate model rather than other alternatives which include the solvent fraction as one of the model parameters. The termination rate constants in the solution agree, within experimental error, with those in the bulk, showing no particular preference for the cross-termination reactions.