Use of Solvent Effects to Improve Control Over Nitroxide‐Mediated Polymerization of Isoprene

Abstract

The use of 1,4-dioxane or pyridine as solvents for the polymerization of isoprene mediated by the acid-functional SG1-based alkoxyamines N-(2-methylpropyl)-N-(1-diethylphosphono-2,2-dimethylpropyl)-O-(2-carboxylprop-2-yl)hydroxylamine (BlocBuilder MA) and N-(2-methylpropyl)-N-(1-diethylphosphono-2,2-dimethylpropyl)-O-(2-carboxyleth-2-yl)hydroxylamine results in an increase in the rate of consumption of the initiator and narrower molecular weight distributions of the resulting polymer. In pyridine, an improved control of the polymerization was also obtained for a non-acid-functional initiator, and the overall rate of polymerization increased. These effects are likely to be the result of the disruption of intramolecular hydrogen bonding and, in the case of pyridine, stabilization of the polar SG1 free radical.

H‐transfer reaction during decomposition of N‐(2‐methylpropyl)‐ N‐(1‐diethylphosphono‐2,2‐dimethylpropyl)‐N‐oxyl (SG1)‐based alkoxyamines

“…Decomposition of 13 mM of alkoxyamine yields 7 mM of diethylphosphite and only traces of alkene. These results mean that the presence of carboxylic function in alkoxyamine involves different pathway of decomposition due to intramolecular H‐bonding46, 47 as tentatively is displayed in Supporting Information Scheme 3. In addition, degradation of SG1 can be induced by the acid leading to various side‐products.…”

Isoprene (co)polymers with glycidyl methacrylate via bimolecular and unimolecular nitroxide mediated radical polymerization

“…However, these schemes are highly sensitive to impurities and to the presence of functional groups, so that products based on these substrates containing polar groups such as maleic anhydride (MAH) or GMA are of great value and potential commercial impact. To overcome the limitations posed by the sensitivity of the synthesis techniques mentioned above, FRPs, which possess an inherent robustness, can be advantageously applied to the (co)polymerization of 1,3‐dienes, especially if it is desired to impart some polarity to the final polymer . This can be better done by using controlled radical polymerization (CRP), which is one of the most powerful techniques available today for the synthesis or modification of polymers.…”

“…There are a few studies based on the (co)polymerization of isoprene in CRP . A very recent and thorough review of RAFT (reversible addition fragmentation chain‐transfer) polymerization of dienes by Moad, emphasizes the increasing interest of the scientific community in the broad subject of CRP polymerization of dienes.…”

Reversible addition-fragmentation chain transfer (co)polymerization of conjugated diene monomers: butadiene, isoprene and chloroprene

“…). It is not surprising, therefore, that the advent of RDRP has seen a number of groups apply various techniques, namely nitroxide‐mediated polymerization (IUPAC term is aminoxyl‐mediated polymerization), atom transfer radical polymerization (ATRP), iodine transfer polymerization, tellurium‐mediated radical polymerization and RAFT ( vide infra ), in attempts to control radical polymerization of conjugated diene monomers and provide a route to low‐dispersity polymers with better defined architecture and composition.…”