Deterministic Modeling of Degenerative RAFT Miniemulsion Polymerization Rate and Average Polymer Characteristics: Invalidity of Zero–One Nature at Higher Monomer Conversions

The polymerization rate and average polymer characteristics of degenerative reversible addition–fragmentation chain transfer (RAFT) miniemulsion polymerization of methyl methacrylate with cyanoprop-2-yl dithiobenzoate as initial RAFT agent (R₀X) and potassium persulfate as initiator are studied at 333 K up to monomer conversions of 95%, considering a two-dimensional Smith–Ewart model. This model accounts for the number of macroradicals and R₀ radicals per nanoparticle, an average particle size between 50 and 500 nm, targeted chain lengths (TCLs) between 50 and 600, exit/entry of R₀ radicals, and the possible influence of diffusional limitations on termination and RAFT transfer at the microscale. The accuracy of the microscale model parameters is highlighted by a successful description of bulk literature data, and the interphase mesoscale parameters are determined based on literature miniemulsion data at various average particle sizes. It is demonstrated that at high monomer conversions it is not afforded to assume zero–one kinetics due to diffusional limitations on termination. With larger average chain lengths this deviation is more pronounced and further accelerated by diffusional limitation on RAFT transfer. Even though the miniemulsion kinetics are faster than the bulk counterpart, retardation due to consecutive entry/exit events of R₀ radicals can be observed as long as R₀X is present.