Reversible addition–fragmentation chain transfer polymerization of methyl methacrylate in emulsion

Abstract

Theoretical simulations showed that for controlled/living radical polymerization in an emulsion system, some of the earliest born particles could be superswollen to a size close to 1 lm. We hypothesized that the superswelling of these particles would lead to colloidal instability. Under the guidance of the simulation results, reversible addition-fragmentation chain transfer (RAFT) emulsion polymerization of methyl methacrylate (MMA) was carried out. Experimental results showed that increasing the initiation rate, surfactant level, and targeted molecular weight could improve the colloidal stability of the RAFT polymerization of MMA in an emulsion. The experimental results were in full accord with the theoretical predictions. The poor control of the molecular weight and polydispersity index was found to have a close relationship with the colloidal instability. For the first time, we demonstrated that RAFT polymerization could successfully be implemented with little coagulum, good control of the molecular weight, and a low polydispersity index with the same process used for traditional emulsion polymerization but with higher surfactant levels and initiation rates.

Comparison of RAFT polymerization of methyl methacrylate in conventional emulsion and miniemulsion systems

“…It has been reported that increasing the amount of surfactant could enhance the stability of RAFT polymerization in both emulsion and miniemulsion systems [21,32]. Considering this point, we increased the amount of SDS from original 0.25 g to 0.60 g (Exp.…”

Living Radical Polymerization by the RAFT Process—A First Update

“…[135] [61] S/VBSC [62] 8* AN [63] (DBI) [64] DMAEMA [65] 9* (DBI) [64] DMAEMA [68] GMA [68] HPMAM/NMS [66] MMA [67] HEMA [68] (MA) [69] MMA [46,70,71] NIPAM [72] PFMA [73] (S) [44,74] S [75] S [76] S/AN [68] S/MAH [68] S S CN S S CN…”

“…A large number of recent studies relate RAFT polymerization in heterogeneous media (emulsion, [67,74,81,98,117,122,139,[161][162][163][164][165][166] miniemulsion, [10,76,[167][168][169][170][171][172][173][174][175] or suspension [176] ). The area has been reviewed by McCleary and Klumperman [11] and Save et al [177] 'Surfactant free' emulsion polymerization making use of a hydrophilic macroRAFT agent (typically based on PAA oligomer formed with RAFT agent 67) [117,161,163,164] has been used for BA [117] and styrene.…”

“…[67] Hartmann et al [98] have studied the effect of degassing on latex stability in RAFT emulsion polymerization of styrene with dithiophenylacetate 39 (bimodal distribution) or xanthate 72 (broad distribution but good control). They report that the use of surfactant-free polymerization media degassed through freeze-pump-thaw cycles provides stable emulsions whereas nitrogen degassing does not.…”

Polymer chain extension in semibatch emulsion polymerization with RAFT‐based transfer agent: The influence of reaction conditions on polymerization rate and product properties

“…LFRP techniques have also been extended to heterogeneous polymerizations such as emulsion and suspension polymerization. [8][9][10][11][12] LFRP with heterogeneous polymerization is an active research area as it provides a powerful tool for preparing tailor-made products and promises substantial practical applications. Three major LFRP techniques are nitroxide-mediated polymerization (NMP), 5 atom transfer radical polymerization (ATRP), 3 and reversible addition-fragmentation chain transfer (RAFT).…”