Synthesis and characterization of amphiphilic heterograft copolymers with PAA and PS side chains via “Grafting from” approach

The amphiphilic heterograft copolymers poly(methyl methacrylate-co-2-(2-bromoisobutyryloxy)ethyl methacrylate)-graft-(poly(acrylic acid)/polystyrene) (P(MMA-co-BIEM)-g-(PAA/PS)) were synthesized successfully by the combination of single electron transfer-living radical polymerization (SET-LRP), single electron transfer-nitroxide radical coupling (SET-NRC), atom transfer radical polymerization (ATRP), and nitroxide-mediated polymerization (NMP) via the “grafting from” approach. First, the linear polymer backbones poly(methyl methacrylate-co-2-(2-bromoisobutyryloxy)ethyl methacrylate) (P(MMA-co-BIEM)) were prepared by ATRP of methyl methacrylate (MMA) and 2-hydroxyethyl methacrylate (HEMA) and subsequent esterification of the hydroxyl groups of the HEMA units with 2-bromoisobutyryl bromide. Then the graft copolymers poly(methyl methacrylate-co-2-(2-bromoisobutyryloxy)ethyl methacrylate)-graft-poly(t-butyl acrylate) (P(MMA-co-BIEM)-g-PtBA) were prepared by SET-LRP of t-butyl acrylate (tBA) at room temperature in the presence of 2,2,6,6-tetramethylpiperidin-1-yloxyl (TEMPO), where the capping efficiency of TEMPO was so high that nearly every TEMPO trapped one polymer radicals formed by SET. Finally, the formed alkoxyamines via SET-NRC in the main chain were used to initiate NMP of styrene and following selectively cleavage of t-butyl esters of the PtBA side chains afforded the amphiphilic heterograft copolymers poly(methyl methacrylate-co-2-(2-bromoisobutyryloxy)ethyl methacrylate)-graft-(poly(t-butyl acrylate)/polystyrene) (P(MMA-co–BIEM)-g-(PtBA/PS)). The self-assembly behaviors of the amphiphilic heterograft copolymers P(MMA-co–BIEM)-g-(PAA/PS) in aqueous solution were investigated by AFM and DLS, and the results demonstrated that the morphologies of the formed micelles were dependent on the grafting density. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011