The role of excess nitroxide in the SG1 (N‐tert‐butyl‐N‐[1‐diethylphosphono‐(2,2‐dimethylpropyl)] nitroxide)‐mediated polymerization of methyl methacrylate

Abstract

Methyl methacrylate (MMA) polymerizations have been conducted in the presence of large excesses of N-tert-butyl-N-[1-diethylphosphono-(2,2-dimethylpropyl) nitroxide] (SG1) at 1108C. It is demonstrated that such a protocol does not improve control/livingness in the nitroxide mediated polymerization (NMP) of this monomer, instead substantial levels of disproportionation between the nitroxide and propagating radical (PMMA l ) results. The extent of the disproportionation reaction increased with the SG1 concentration, eventually becoming the sole end forming event. Significant disproportionation between SG1 and PMMA l was also observed at substantially lower temperatures (458C) in the presence of large excesses of SG1. V V C 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45:

Nitroxide‐mediated radical polymerization of carbon dioxide‐expanded methyl methacrylate

“…A significant drawback of NMP is that it is in general incompatible with alkyl methacrylates [5][6][7][8][9] primarily due to the tendency of nitroxide radicals and the corresponding propagating radicals to undergo disproportionation generating a hydroxylamine and a dead chain with an unsaturated end group. 10,11 This reaction may also proceed unimolecularly, although it has been shown for the present system that the bimolecular pathway is predominant. 6,12,13 It was reported in 2007 that the nitroxide known as 2,2-diphenyl-3-phenylimino-2,3-dihydroindol-1-yloxyl nitroxide (DPAIO) 14 can be successfully used for NMP of methyl methacrylate (MMA) because of the absence of such disproportionation reactions.…”

“…5), assigned to the unsaturated x end group of PMMA. 10 M n (NMR) was estimated by comparison of the relative intensities of the 1 H NMR resonances of the unsaturated end group with the resonance of the methoxy (OCH 3 ) group, that is, based on the assumption that each polymer chain bears one unsaturated end group. The number of unsaturated end groups per polymer chain (f) was subsequently estimated via eq 1 10 :…”

“…If termination by disproportionation is the only pathway to unsaturated chain ends, the maximum value of f is 0.5, and k td /k tc ¼ 4.37 corresponds to f ¼ 0.45. 10 The value of f was estimated for polymerizations with and without CO 2 (the data point at the highest conversion in each data series), resulting in f ¼ 0.84 (without CO 2 ) and 0.78 (with CO 2 ). Thus, the average number of unsaturated end groups per chain was slightly lower in the presence of CO 2 .…”

Controlled Photoradical Polymerization Mediated by 2,2,6,6-Tetramethylpiperidine-1-Oxyl

“…Thermal NMP at high temperatures often causes hydrogen abstraction by the nitroxide mediator from the propagating radical [64,65]. Photopolymerization carried out at room temperature can eliminate this side reaction.…”

Block copolymer synthesis by controlled/living radical polymerisation in heterogeneous systems

“…213,66 However, the co-monomers St 171 or sodium 4-styrene sulfonate (SS) 172 (~ 10 mol%) were necessary to achieve controlled synthesis of PMAA-SG1, a well-known strategy for NMP of methacrylates. 226,227 Non-spherical block copolymer nano-objects can also be obtained by nitroxidemediated emulsion polymerisation. This was achieved during the one-pot synthesis of PAA-b-P4VP, 228 in which PNaA21-SG1 was first synthesised in water at 120 °C and pH 11, and then used as the initiator for controlled polymerisation of 4VP under the same conditions (at which 4VP and P4VP were insoluble).…”