Controlled Synthesis of High Molecular Weight Polyacrylates Having a Dumbbell Topology

Well-defined high molecular weight (MW) (M n ∼ 500 000, M w/M n < 1.2) dumbbell-shaped copolymers based on butyl acrylates (BA) were synthesized by atom transfer radical polymerization (ATRP) in acetone. The synthesis was carried out by polymerization of BA initiated by a difunctional ATRP initiator. The resulting difunctional bromine end-functionalized PBA was used to initiate a small amount of hydroxyethyl acrylate (HEA). The resulting ABA type copolymer containing two short poly(hydroxyethyl acrylate) end blocks was reacted with α-bromoisobutyryl bromide. The resulting ABA polymer was used to reinitiate additional BA end arms to afford the desired dumbbell PBA. All polymer intermediates and the final polymer were characterized by NMR and multiangle laser light scattering size exclusion chromatography (SEC-MALLS). SEC analysis of the low-MW polymers obtained by base hydrolysis of the intended structure confirmed the successful BA polymerization at the A blocks. Hydrolysis gave the expected number and MWs of the grafted chains.