Front Cover: General analytic formulas for the number‐ and weightaverage molecular weights of the core cross‐linked star polymers are proposed. The method to extract important structural information from the experimentally measurable quantities is discussed. The full MWD profiles could be estimated by using the Monte Carlo simulation method. This is reported by Hidetaka Tobita in article number 1600037.

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In free‐radical olefin polymerizations, the polymer transfer reactions could lead to chain scission as well as forming long‐chain branches. For the random scission of branched polymers, it is virtually impossible to apply usual differential population balance equations because the number of possible scission points is dependent on the complex molecular architecture. On the other hand, the present problem can be solved on the basis of the probability theory by considering the history of each primary polymer molecule in a straightforward manner. The random sampling technique is used to solve this problem and a Monte Carlo simulation method is proposed. In this simulation method, one can observe the structure of each polymer molecule formed in this complex reaction system, and virtually any structural information can be obtained. In the illustrative calculations, the full molecular weight distribution development, the gel point determination, and examples of two‐ and three‐dimensional polymer structure are shown. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 391–403, 2001

A new MC simulation method is proposed for the controlled/living radical polymerization in a dispersed medium, assuming an ideal miniemulsion system. This tool is used to consider the effects of particle size on the polymerization rates and the molecular weight distributions. For NMP, the polymerization kinetics are basically governed by two conflicting factors, (i) the confined space effect that promotes the coupling reaction between a radical and a trapping agent and (ii) the isolation effect of radicals into different particles that suppresses the overall frequency of bimolecular termination. For RAFT polymerization, a significant rate enhancement by reducing the particle size could be observed only for the systems with fast fragmentation of adduct radicals.magnified image

SUMMARY Comprehensive accounts for the newly proposed concept of the random sampling technique are given in detail. This techniques involves random sampling of polymer molecules from an infinite number of polymeric species in the reaction mixture, and can provide a deeper insight into the complex molecular buildup processes such as those involving branching, crosslinking, and degradation reactions. For simpler cases, the analytical solutions for the molecular weight distribution can be obtained. By combining this technique with the Monte Carlo method, one obtains a very powerful simulator that can be applied to virtually any type of nonlinear polymer formation (or degradation) irrespective of the reactor types used, as long as the chain‐length and structural dependences of the reaction kinetics can be neglected. In the Monte Carlo simulations, we can observe the structure of each polymer molecule directly so that very detailed structural information, including the spatial distribution of polymer chains, can be obtained in a straightforward manner. Several types of nonlinear polymerization schemes are used to illustrate the fundamentals of the presented technique.