A SIMULATION-MODEL FOR LONG-CHAIN BRANCHING IN VINYL-ACETATE POLYMERIZATION .1. BATCH POLYMERIZATION

A new simulation model for the kinetics of long-chain branching formed via chain transfer to polymer and terminal double-bond polymerization is proposed. This model is based on the branching density distributio n of the primary polymer molecules. The theory of branching density di stribution is that each primary polymer molecule experiences a differe nt history of branching and provides information on how each primary p olymer molecule is connected with other chains that are formed at diff erent conversions, therefore making possible a detailed analysis on th e kinetics of the branched structure formation. This model is solved b y applying the Monte Carlo method and a computer-generated simulated a lgorithm is proposed. The present model is applied to a batch polymeri zation of vinyl acetate, and various interesting structural changes oc curring during polymerization (i.e., molecular weight distribution, di stribution of branch points, and branching density of the largest poly mer molecule) are calculated. The present method gives a direct soluti on for the Bethe lattice formed under nonequilibrium conditions; there fore, it can be used to examine earlier theories of the branched struc ture formation. It was found that the method of moments that has been applied successfully to predict various average properties would be co nsidered a good approximation at least for the calculation of not grea ter than the second-order moment in a batch polymerization. (C) 1994 J ohn Wiley & Sons, Inc.