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

International audience• 4VP is an efficient controlling comonomer for NMP of MMA and PEOMA. • 4VP is unable to control the NMP of methacrylic acid. • Successful formation of 4VP-based block copolymers by chain extension. • Chain extension in the presence of silica particles yields raspberry-like composite colloids. A B S T R A C T 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 (PEOMA 950 , M n = 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 PEOMA 950 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(MMA 72-co-4VP 10)-SG1 macroalkoyamine was then successfully used to reinitiate the copolymerization of n-butyl metha-crylate (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