(262f) Modeling of Crosslinking In Free-Radical Polymerization

Since the pioneering studies of Flory and Stockmayer many different models have been introduced to describe crosslinking in free-radical polymerization. Purely kinetical, statistical, Monte Carlo and combinations of these models have been proposed.

In the present work, a mixed statistical/kinetic model, based on Flory’s gelation theory and on Tobita’s extension of it, has been developed. The most important cyclization reactions have been implemented in a classical population balance equation scheme and a thorough sensitivity analysis, focusing on the cyclization rate constants, has been performed. The influence of these rate constants has been evaluated in terms of their effect on system properties such as gelation time, crosslinking density distribution, elasticity and molecular weight distribution between crosslinks. The birth time of the chains and the “actual” time, at which the polymerization occurs, had to be distinguished as the crosslinking distribution has been proven to be non-random in time. The present model describes bulk and heterogeneous crosslinking copolymerization and has been validated by comparison with Monte Carlo simulations.