Controlled Radical Polymerization at High Conversion: Bulk ICAR ATRP of Methyl Methacrylate

Abstract

Methyl methacrylate (MMA) was polymerized in bulk via atom transfer radical polymerization (ATRP) with azobis(isobutyronitrile) (AIBN) and tert-butyl peroxybenzoate (TBPB) as initiator for continuous activator regeneration (ICAR). The ATRP was first carried out up to high conversion at 70 °C. When the system reached its glass state at about 94%, the polymerization temperature was elevated to 120 °C to maximize the conversion. Livingness of the ICAR ATRP process and control of polymer molecular weight at high conversion were carefully examined to elucidate the mechanisms of diffusioncontrolled reactions. The "gel effect" started at about 50% conversion, and it was accompanied by molecular weight distribution broadening. A dramatic increase in polydispersity was observed at above 90% conversion. The loss of control over molecular weight was caused by diffusion-controlled deactivation, which could be reduced to some extent by increasing deactivator concentration. However, despite the loss of control at high conversion, livingness of the system did not suffer, owing to diffusioncontrolled termination. The polymer chains collected at very high conversion could be easily extended with high efficiency.

Electrochemical Atom Transfer Radical Polymerization in Miniemulsion with a Dual Catalytic System

“…43–49 Currently, however, several catalyst (re)-generation methods allow performing ATRP reactions with low ppm levels of catalysts; these techniques include activators regenerated by electron transfer (ARGET) ATRP, 50–58 initiators for continuous activator regeneration (ICAR) ATRP, 50,59–65 supplemental activator and reducing agent (SARA) ATRP, 66–73 photoinduced ATRP (photoATRP), 74–85 85 and electrochemically mediated ATRP ( e ATRP, the method used in this work). 86–97 …”

Modeling the Influence of Diffusion-Controlled Reactions and Residual Termination and Deactivation on the Rate and Control of Bulk ATRP at High Conversions

“…The reactants are monomer, initiator and catalyst with the initial concentrations of [M] In our previous study [13], the bulk ATRP of methyl methacrylate (MMA) was carried out up to very high conversions. The results showed that although the livingness of polymer chains was preserved because of the diffusion-controlled termination, the control over polymer molecular weight was lost because of the diffusion-controlled deactivation.…”

“…In CRP, it is the diffusion-controlled deactivation that is responsible for the "gel effect" occurring. Diffusion-controlled termination in CRP is considered as an asset that helps the livingness of polymer chains [13,16].…”

Pushing Monomer Conversions High in Bulk ATRP: The Effects of ICAR Agent Concentrations on the System Livingness and Polymer Molecular Weight Control

“…The high catalyst loading gives deep color to the final ATRP products and makes the post purification costly (8). The high conversion in bulk causes diffusion control problem for those reactions involving chain species and loss of control of the reaction (9). Solution polymerization is often employed.…”

“…In contrast, the problem associated with high conversion has not been addressed thoroughly. The high conversion problem is attributed to diffusion-controlled reactions, which cause "gel effect" and "glass effect" and make the system suffer from loss of control and result in high dispersity (Đ) (9,13,14).…”