Nitroxide-mediated Polymerization Of Methyl Methacrylate Research Articles

Nitroxide-mediated polymerization of methacrylates in the presence of 4-vinyl pyridine as controlling comonomer

The controlled polymerization of methacrylic monomers by nitroxide-mediated polymerization (NMP) still represents a challenge in polymer science. This issue can be circumvented by the addition of a small amount of a comonomer known to exhibit a controlled character in NMP, the most representative example being styrene. The purpose of this work is to explore the use of 4-vinyl pyridine (4VP) as controlling comonomer, while conferring at the same time some functionality to the polymer chains. The NMP of methyl methacrylate (MMA), poly(ethylene glycol) methyl ether methacrylate (PEOMA950, Mn = 950 g mol−1) and methacrylic acid (MAA) using a small amount of 4VP under mild experimental conditions (<90 °C, atmospheric pressure), was investigated in this work. The copolymerization of MMA or PEOMA950 with 10 mol% 4VP, mediated by the use of the BlocBuilder® alkoxyamine and a small amount of free nitroxide SG1, exhibited all the features of a controlled system in agreement with the favored incorporation of 4VP at the chain ends, leading to an efficient deactivation of the propagating radicals by the nitroxide SG1. In contrast, the polymerization of MAA was uncontrolled in the same conditions likely due to acid/base interaction between MAA and 4VP, affecting the reactivity of the functional comonomer. Consistently, the copolymerization of MAA with MMA also led to a progressive loss of control as the MAA content in the feed was increased. Among all the polymers synthesized, the P(MMA72-co-4VP10)-SG1 macroalkoyamine was then successfully used to reinitiate the copolymerization of n-butyl methacrylate (BMA) and 4VP both in solution and via dispersion polymerization in a mixture of ethanol and water. Finally, raspberry-like polymer/silica composite particles were prepared through nitroxide-mediated dispersion polymerization performed in the presence of silica nanoparticles, taking benefit of the strong acid-base interaction between 4VP and silica.

An evaluation of the impact of SG1 disproportionation and the addition of styrene in NMP of methyl methacrylate

A kinetic modeling study is presented for batch nitroxide mediated polymerization (NMP) of methyl methacrylate (MMA; nitroxide: N‐tert‐butyl‐N‐[1‐diethylphosphono‐(2,2‐dimethylpropyl)] (SG1)). Arrhenius parameters for SG1 disproportionation (A = 1.4 107 L mol−1 s−1; Ea = 23 kJ mol−1) are reported, based on homopolymerization data accounting for unavoidable temperature variations with increasing time, that is, nonisothermicity. For low targeted chain lengths (TCLs ≤ 300), this nonisothermicity is also relevant for NMP of MMA with a small amount of styrene. Parameter tuning to copolymerization data confirms a penultimate monomer unit effect for activation (sa2 = ka12/ka22=6.7; 363 K; 1: MMA; 2: styrene). To obtain, for a broad TCL range (up to 800), a dispersity well below 1.3 an initial styrene mass fraction of ca. 10% is required. An interpretation of the comonomer incorporation is performed by calculating the fractions of activation‐growth‐deactivation cycles with a given amount of monomer units and the copolymer composition distribution. © 2018 American Institute of Chemical Engineers AIChE J, 64: 2545–2559, 2018

Efficient synthesis of 2-methylene-4-phenyl-1,3-dioxolane, a cyclic ketene acetal for controlling the NMP of methyl methacrylate and conferring tunable degradability

The efficient and reliable synthesis of 2-methylene-4-phenyl-1,3-dioxolane (MPDL) was reported and MPDL was used as a controlling comonomer for nitroxide-mediated polymerization of methyl methacrylate to give degradable copolymers.

Nitroxide-mediated polymerization of methyl methacrylate by 4,4′-dimethoxydiphenyl-based alkoxyamine

4,4′-Dimethoxydiphenyl nitroxide-based alkoxyamine was prepared and used to control the polymerization of methyl methacrylate. Linear increase in molecular weight with conversion and narrow molecular weight distribution was up to 65% conversion.

Stereocontrol of Methyl Methacrylate during Photoinduced Nitroxide-Mediated Polymerization in the Presence of Photosensitive Alkoxyamine

Photosensitive alkoxyamine 2,2,6,6-tetramethyl-1-(1-phenylethoxy)piperidin-4-yl quinoline-2-carboxylate (PE-TEMPO-Q) was synthesized. Photochemical properties of PE-TEMPO-Q were studied to develop photoinduced nitroxide-mediated polymerization of methyl methacrylate (MMA). Rapid and facile polymerization at ambient temperature with PE-TEMPO-Q as an initiator was confirmed to proceed in a controlled mechanism based on the linear growth in molecular weight combined with relative narrow polydispersity index (1.4–1.8) of the resulting polymers. The stereochemistry of obtained polymers was also investigated, and the syndiotacticity slightly increased compared with the typical photopolymerization. Dual-controlled photopolymerization of MMA was achieved in the presence of synthesized alkoxyamine.

Nitroxide-Mediated Polymerization of Methyl Methacrylate and Styrene with New Alkoxyamines from 4-Nitrophenyl 2-Methylpropionat-2-yl Radicals

The N-phenylalkoxyamine N-(1-methyl-(1-(4-nitrophenoxy)carbonyl)ethoxy)-N-(1-methyl-(1-(4-nitrophenoxy)carbonyl)ethyl)benzenamine (1) was prepared by the addition of 4-nitrophenyl 2-methylpropionat-2-yl radicals across the double bond of nitrosobenzene and evaluated as an initiator for nitroxide-mediated polymerization (NMP). N-Phenylalkoxyamines have not been extensively studied in NMP, though they have shown promise in controlling methyl methacrylate (MMA) polymerization to moderate conversions. It is thought that delocalization of the nitroxide radical through the N-phenyl substituent may minimize cross-disproportionation of the nitroxide with the chain end that has made NMP of MMA difficult. Here, we show that alkoxyamine 1 is capable of controlling the NMP of MMA to 50% conversion while maintaining narrow molecular weight distributions (Mw/Mn = 1.12−1.30). Additionally, chain extension from the resulting PMMA macroinitiators with MMA or styrene allows the formation of diblock copolymers. The correspo...

A minimal amount of acrylonitrile turns the nitroxide‐mediated polymerization of methyl methacrylate into an almost ideal controlled/living system

AbstractNitroxide‐mediated controlled/living free‐radical polymerization of methyl methacrylate initiated by the SG1‐based alkoxyamine BlocBuilder was successfully performed in bulk at 80–99 °C with the help of a very small amount of acrylonitrile (AN, 2.2–8.8 mol %) as a comonomer. Well‐defined PMMA‐rich P(MMA‐co‐AN) copolymers were prepared with the number‐average molar mass, Mn, in the 6.1–32 kg mol−1 range and polydispersity indexes as low as 1.24. Incorporation of AN in the copolymers was demonstrated by 1H and 13C NMR spectroscopy, and its effect on the chain thermal properties was evaluated by DSC and TGA analyses. Investigation of chain‐end functionalization by an alkoxyamine group was performed by means of 31P NMR spectroscopy and chain extensions from a P(MMA‐co‐AN)‐SG1 macroinitiator. It demonstrated the very high proportion of SG1‐terminated polymer chains, which opened the door to block copolymer synthesis with a high quality of control. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 34–47, 2010

First Effective Nitroxide-Mediated Polymerization of Methyl Methacrylate

Bulk methyl methacrylate (MMA) controlled radical polymerization was carried out using two 2,2-diphenyl-3-phenylimino-2,3-dihydroindol-1-yloxyl nitroxide (DPAIO) based alkoxyamines. Whatever the alkoxyamine used, polymerization presents a controlled character, and high conversion can be reached. Polymerization up to 60% conversion, initiated with the nitro para-substituted alkoxyamine 2, showed a linear increase of number-average molecular weight (Mn) vs conversion even at the beginning of the polymerization with the final polydispersity index (PDI) close to 1.4. A reinitiation test onto n-butyl acrylate has shown that even if this nitroxide is not suited for acrylate monomers, the shift of the size exclusion chromatography (SEC)trace proved the poly(methyl methacrylate)−DPAIO macroinitiator (PMMA−DPAIO) obtained had a living character. These results showed that the range of monomers that could be polymerized by nitroxide mediated polymerization (NMP) can still be extended.

Theoretical Expression of the Average Activation−Deactivation Equilibrium Constant in Controlled/Living Free-Radical Copolymerization Operating via Reversible Termination. Application to a Strongly Improved Control in Nitroxide-Mediated Polymerization of Methyl Methacrylate

The average activation−deactivation equilibrium constant, 〈K〉, was determined on a theoretical basis for controlled free-radical copolymerizations operating via a reversible termination mechanism (i.e., nitroxide-mediated polymerization or atom transfer radical polymerization), using the terminal model for the activation−deactivation equilibrium and the terminal model or the implicit penultimate unit effect model for the propagation reaction. From the equation, it was shown that the addition of a small fraction of an appropriate comonomer to a monomer with a very large activation−deactivation equilibrium constant, K, might lead to strong reduction of 〈K〉, providing the added comonomer exhibits a low K. In nitroxide-mediated polymerization, the monomers with a very high K, such as the methacrylic esters, do not lead to controlled polymerization in the presence of nitroxides like SG1, despite the absence of disproportionation reaction between the nitroxide and the growing radical, because of the too fast irreversible self-termination of the propagating radicals present in high concentration. The polymerization stops at low conversion. Consequently, a reduction of K might lead to an enhanced quality of control. The method was indeed successfully applied to the SG1-mediated polymerization of methyl methacrylate at 90 °C. By adding only 4.4 or 8.8 mol % of styrene, the polymerization could be carried out to large conversions, while exhibiting all the features of a controlled system.