ABSTRACT
On the basis of the branching density distribution proposed earlier (Tobita, 1992a), a new theory for the kinetics of nonlinear free-radical polymerization that involves chain transfer to polymer is proposed. The present theory in which the history of each primary polymer molecule is properly accounted for is quite general and can be applied to various complex polymerization systems that include branching, crosslinking, and degradation of polymers. The present theory is solved by application of Monte Carlo method and a simulation algorithm for the molecular weight distribution (MWD) is developed. It was found that simulation of growth for only about 1000 polymer molecules is enough for practical purposes and that the simulation algorithm can be handled on a personal computer. It was shown clearly why gelation never occurs by chain transfer to polymer without assistance of other inter-linking processes such as bimolecular termination by combination irrespective of the reactor types used. The present simulation method gives direct solution for the Bethe lattice formed under nonequilibrium conditions, and therefore, it can be used to examine the earlier theories of branched structure formation. It was found that the method of moments that has been applied successfully to a batch polymerization cannot be applied to a continuous stirred tank reactor.
