Synthesis and pH-dependent micellization of 2-(diisopropylamino)ethyl methacrylate based amphiphilic diblock copolymers via RAFT polymerization

The polymerization of 2-(diisopropylamino)ethylmethacrylate (DPA) by RAFT mechanism in the presence of 4-cyanopentanoic acid dithio-benzoate in 1,4-dioxane was studied. The DPA homopolymer was employed as a macro chain transfer agent to synthesize pH-sensitive amphiphilic block copolymers using poly(ethylene glycol) methyl ether methacrylate (PEGMA) as the hydrophilic block. H-1 NMR and GPC measurements confirmed the successful synthesis of these copolymers. Potentiometric titrations and fluorescence experiments proved that the copolymers underwent a sharp transition from unimers to micelles at a pH of similar to 6.7 in phosphate buffered saline solutions. It was found that the hydrophilic/hydrophobic balance of these block copolymers had no apparent effect on their pH-induced micellization behaviors. The DLS investigation revealed that the micelles have a mean hydrodynamic diameter below 60 rim with a narrow size distribution. (C) 2007 Elsevier Ltd. All rights reserved.