A new strategy for the synthesis of methacrylate end-functionalized macromonomers by ATRP
Résumé
The influence of the polymerization temperature, the [CuBr]0/[PMDETA]0 ratio, and the monomer conversion on the chain-end functionality of poly(ethyl acrylate)s (PEAs) was studied during the atom transfer radical polymerization (ATRP) of ethyl acrylate (EA) using CuBr/N,N,N′,N′,N″-pentamethyldiethylenetriamine (PMDETA) as a catalyst system and ethyl-2-bromo-2-methylpropionate (EBiB) as an initiator. The presence of bromine chain-end of PEA was checked by MALDI-TOF spectrometry and by chain-extension reaction. It was shown that ATRP of EA performed with [EA]0/[EBiB]0/[CuBr]0/[PMDETA]0 ratios of 25/1/0.5/0.5 in toluene at 50 °C allows to obtain a quantitative functionality of halide end-groups of PEA up to 66% monomer conversion. Well-defined poly(ethylene oxide)-b-poly(ethyl acrylate) PEO-b-PEA bearing bromide chain-ends were obtained by the ATRP of EA using PEO-Br as a macroinitiator under previous experimental conditions. A more detailed study of PEO-b-PEA block copolymers synthesis was previously published (Piogé et al., Macromolecules 2009, 42, 4262–4272). These end-groups were transformed into methacrylate end-groups by a two-step pathway. An original approach to generate hydroxyl end-groups was based on the nucleophilic substitution of the halogen end-groups using different mercaptoalcohols. Using 6-mercaptohexan-1-ol, a quantitative functionalization was observed. In a second step, hydroxyl groups were esterified quantitatively with methacryloyl chloride, and the resulting methacrylate end-functionalized PEO-b-PEA macromonomers have well-defined molecular weights and low polydispersities.