Molecular weight distribution of living radical polymers - 2. Monte Carlo simulation

A new Monte Carlo simulation method is proposed for the living radical polymerization on the basis of the random sampling technique. The stable free-radical polymerization is used as a specific reaction mechanism. The illustrative calculations are conducted to investigate the effects of simultaneous use of two different types of radical initiators, with a large and a small decomposition rate constant. The addition of second initiator that decomposes slowly leads to a significant increase in the polymerization rate. The increased frequency of forming the dead and new growing polymer chains makes the molecular weight distribution (MWD) broader. On the other hand, however, there exists a weak but definite factor to reduce the polydispersity, which may compensate the broadening. On the basis of the simulation studies, one may find an excellent reaction condition to produce polymer with a higher productivity, having a larger MW, and with a narrow distribution. The effect of the monomer trans-fer reactions on the formed MWD is investigated to find that the transfer reactions must be accounted for when the designed number-average chain length is larger than about 10% of 1/C(m), where C(m) is the monomer transfer constant.