MONTE-CARLO SIMULATION OF KINETICS AND CHAIN-LENGTH DISTRIBUTION IN RADICAL POLYMERIZATION

In this paper, the Monte Carlo method for numerically simulating the k inetics and chain-length distribution in radical polymerization is des cribed. Because the Monte Carlo method is not subject to the assumptio n of steady-state, it is particularly suitable for studying the kineti c behaviour before the steady-state has been reached and for systems i n which the steady-state assumption may be violated. Illustrative appl ications of the algorithm given in this paper not only demonstrate con vincingly both the feasibility and usefulness of the algorithm, but al so provide some new insight into the illustrative examples. For the ca se of pseudostationary radical polymerization such as rotating-sector and pulsed-laser initiations, we have found that the pseudostationary radical concentration can be reached after two or three initiation per iods. However, the number-average chain-length x(n)BAR reaches the pse udostationary value much slower than the radical concentration. It is oscillatively reaching the pseudostationary value, and the amplitudes of the oscillations are decreasing with time. We have also found that the chain-length distribution of the resulting polymer in the case of pseudostationary radical polymerization with termination by combinatio n has stronger periodic modulation. Hence, it should be easier to loca te the points of inflection in practice. Therefore, the rate constant of propagation, k(p), can be determined precisely for systems which ar e dominated by a combination-type of termination.