Kinetic model of reversible addition fragmentation chain transfer polymerization of styrene in seeded emulsion

Abstract

A detailed model describing the kinetics of living polymerization mediated by reversible addition-fragmentation chain transfer (RAFT) in seeded emulsion polymerization is developed. The model consists of a set of population balance equations of the different radical species in the aqueous phase and in the particle phase (accounting for radical segregation) as well as for the dormant species in the particle phase. The entire population of radicals was divided into several distinguished species, based on their length and their chain end group. The model results are helpful in understanding inhibition and retardation phenomena that are typical for RAFT emulsion polymerizations. While inhibition is due to the radical loss in form of the RAFT leaving group, retardation is mostly caused by a small amount of short dormant chains in the particle phase, leading to a slight increase of radical loss via RAFT exchange with radicals entering a particle. The model results are compared to a series of experiments, using cumyl dithiobenzoate as a RAFT agent in polymerizations of styrene. The agreement between experimental and model results is good and, notably, the only parameters considered adjustable were the RAFT exchange rate coefficients. V V C 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6114-6135, 2006

“Living”/controlled free radical polymerization of MMA in the presence of cobalt(II) 2‐ethylhexanoate: A switch from RAFT to ATRP mechanism

“…At the same time, the polymerization of MMA in the concurrence of CPDN and CEH maintained the “living”/controlled characteristics and complied with the radical mechanism. It was noteworthy that the retardation effect, a familiar existent in RAFT polymerization48, 51–55 was depressed by the addition of CEH, and the polymerization rates were evidently enhanced with the increase of the CPDN concentration at the same concentration of CEH. These experimental results complied with the expectations that the RAFT polymerization may be transferred into the ATRP with CPDN acting as the initiator of ATRP when CEH was added.…”

Butyl acrylate RAFT polymerization in miniemulsion

“…On the other hand, it has been pointed out that R • could be apt to exit out of particles or mini‐droplets 20, 46. The influence of R • exit on RAFT miniemulsion or seeded emulsion polymerization kinetic has been investigated by Monte Carlo simulation20, 48 and kinetic model 49. The simulations predicted that an inhibition period would be caused by the exit of R • .…”

Controlled/Living Radical Polymerization in Aqueous Miniemulsion

“…Inhibition in RAFT miniemulsion polymerization using low MW RAFT agents is often more important than in bulk due to exit of the RAFT agent leaving group to the aqueous phase. The extent of inhibition will therefore be linked to the hydrophobicity of this leaving group [152,157,158]. Similarly, retardation in RAFT miniemulsion polymerization is generally more severe than in bulk/solution counterparts.…”